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A solid consisting of 12 similiar faces, each of which is rhomb, the angle between any two adjacent face being 120 degrees.

Rhombic Dodecahedron

A solid consisting of 12 similiar faces, each of which is rhomb, the angle between any two adjacent…

"The outer edge is a semicircle, with center at 0, and is divided into 360 parts. Each division is one-half of one degree, and, for convenience, the degrees are numbered from 0 to 180 from both A and B." — Hallock, 1905

Protractor

"The outer edge is a semicircle, with center at 0, and is divided into 360 parts. Each division is one-half…

"A patented frame that can be shoved out of the window and adjusted to any angle; it is made in different sized from 16 in. x 24 in. to 48 in. x 72 in. When not in use, it can be folded up against the wall and occupies but little space." — Hallock, 1905. The frame is used in the blueprint reproduction process.

Painting Frame

"A patented frame that can be shoved out of the window and adjusted to any angle; it is made in different…

"Carte, Guard. Turn wrist with nails upwards; hand on a line with lower part of breast; arm somewhat bent, and elbow inclined a little to the outside; point of foil elevated at an angle of about 15 degrees, and directed at upper part of adversary's breast." — Chambers, 1881

Carte

"Carte, Guard. Turn wrist with nails upwards; hand on a line with lower part of breast; arm somewhat…

"Seconde, Parade. Nails and wrist downward, hand opposed outward, and blade, pointing low, should form an angle of about 45 degrees with the ground." — Chambers, 1881

Seconde

"Seconde, Parade. Nails and wrist downward, hand opposed outward, and blade, pointing low, should form…

"An instrument much employed in land-surveying for the measurement of angles horizontal and verticle." — Chambers, 1881

Theodolite

"An instrument much employed in land-surveying for the measurement of angles horizontal and verticle."…

An outline of a butterfly labeling the different parts of the wings.

Butterfly Outline

An outline of a butterfly labeling the different parts of the wings.

"E represents the scape-wheel turning in a minute, and e its pinion, which is driven by the wheel D having a pinion d driven by the wheel C, which we may suppose to turn in an hour. The arbors of the scape-wheel and hour-wheel are distinct, their pivots-meeting in a bush fixed somewhere between the wheels. The pivots of the wheel, D are set in the frame AP, which rides on the arbors of the hour-wheel and scape-wheel, or on another short arbor between them. The hour-wheel also drives another wheel G, which again drives the pinion f on the arbor which carries the two arms f A, f B; and on the same arbor is set a fly with a ratchet, like a common striking fly, and the numbers of the teeth are so arranged that the fly will turn once for each turn of the scapewheel. The ends of the remontoire arms f A, f B are capable of alternately passing the notches cut half through the arbor of the scape-wheel, as those notches successively come into the proper position at the end of every half minute; as soon as that happens the-hour-wheel raises the movable wheel D and its frame through a small angle; but nevertheless, that wheel keeps pressing on the scape-wheel as if it were not moving, the point of contact of the wheel C and the pinion d being the fulcrum or center of motion of the level A d P." — Encyclopedia Britanica, 1893

Gravity Train Remontoire

"E represents the scape-wheel turning in a minute, and e its pinion, which is driven by the wheel D…

A beautiful bird of a rich yellow color, passing by degrees through olivaceous tints on te rump, wings, and tail, the last blotch with white. The bill is comparatively large and black.

Prothonotary Warbler

A beautiful bird of a rich yellow color, passing by degrees through olivaceous tints on te rump, wings,…

"Three principal parts, the card, the needle on its lower suface, and the case. The whole is enclosed in the compass-box, or binnacle. the term compass is said to have been applied to the instrument because the card involves or compasses the whole plane of the horizon, or because the needle indicates the whole circle of possible variations of direction. The surface of the card is divided by radiating lines into 32 parts, each containing 11 degrees." — Encyclopedia Britannica, 1893

Compass Card

"Three principal parts, the card, the needle on its lower suface, and the case. The whole is enclosed…

A math tool used for measuring angles on blueprints.

Protractor

A math tool used for measuring angles on blueprints.

"The dredges on this pattern, used in Britain for ten years after their first introduction, about the year 1838, were usually small and rather heavy, not more than 12 to 15 inches in length, by 4 or 4.5 inches in width at the mouth. Two scrapers, the length of the dredge-frame, and 1.5 to 2 inches wide, were set at an angle of about 110 degrees to the plane of the dredge's mouth, so that when the dredge was gently hauled along it took hold of the ground and secured anything loose on its surface." — Encyclopedia Britannica, 1893

Ball's Naturalists' Dredge

"The dredges on this pattern, used in Britain for ten years after their first introduction, about the…

"ABCD is a cylinder of glass 1 foot in diameter and 1 foot high. This cylinder is closed by a glass lid pierced centrically by two openings, each about 20 lines wide. Into the middle opening is cemented a glass tube 2 feet high, to the upper end of which is fitted a torsion head; the separate parts of the head are shown larger at the side of the figure. H is a collar cemented to the glass tube; MO a metal disc, divided on the edge into 360 degrees; this disc is fastened to a tube N, which slips into the collar H. K is a button whose neck turns easily in a hole in MO; to the lower part of the button is fastened a small clamp, which seizes the wire of the balance. I is an arm with a small projecting piece which slips over the edge of the disc MO." — Encyclopedia Britannica, 1893

Torsion Balance

"ABCD is a cylinder of glass 1 foot in diameter and 1 foot high. This cylinder is closed by a glass…

"Flat-flame burners, or burners which spread their flame in a broad thin sheet, are of two principal kinds known respectively as "fishtail" and "batwing" burners. The fishtail or union burner has two orifices driller in its surface, which are inclined towards each other at the angle of 90 degrees, so that the issuing currents impinge and spread the flame in a broad sheet." — Encyclopedia Britannica, 1893

Burner

"Flat-flame burners, or burners which spread their flame in a broad thin sheet, are of two principal…

"Flat-flame burners, or burners which spread their flame in a broad thin sheet, are of two principal kinds known respectively as "fishtail" and "batwing" burners. The fishtail or union burner has two orifices driller in its surface, which are inclined towards each other at the angle of 90 degrees, so that the issuing currents impinge and spread the flame in a broad sheet." — Encyclopedia Britannica, 1893

Burner

"Flat-flame burners, or burners which spread their flame in a broad thin sheet, are of two principal…

A molding characterized by a sharp and sudden return from its extreme projection to a reentrant angle.

Quirk Molding

A molding characterized by a sharp and sudden return from its extreme projection to a reentrant angle.

A molding characterized by a sharp and sudden return from its extreme projection to a reentrant angle.

Quirk Molding

A molding characterized by a sharp and sudden return from its extreme projection to a reentrant angle.

A molding characterized by a sharp and sudden return from its extreme projection to a reentrant angle.

Quirk Molding

A molding characterized by a sharp and sudden return from its extreme projection to a reentrant angle.

A molding characterized by a sharp and sudden return from its extreme projection to a reentrant angle.

Quirk Molding

A molding characterized by a sharp and sudden return from its extreme projection to a reentrant angle.

"The nature of the cut itself in pruning is of more consequence, especially in the case of fruit trees, than at first signt may appear. The branches should be separated by a clean cut at an angle of abouot 45 degrees, just at the back of a bud, the cut entering on a level with the base of the bud and passing out on a level with its top, for when cut in this way the wound becomes rapidly covered with new wood, as soon as growth recommences, whereas if the cut is too close the bud is starved, or if less close an ugly and awkward snag is left." — Encyclopedia Britannica, 1893

Pruning

"The nature of the cut itself in pruning is of more consequence, especially in the case of fruit trees,…

"The nature of the cut itself in pruning is of more consequence, especially in the case of fruit trees, than at first signt may appear. The branches should be separated by a clean cut at an angle of abouot 45 degrees, just at the back of a bud, the cut entering on a level with the base of the bud and passing out on a level with its top, for when cut in this way the wound becomes rapidly covered with new wood, as soon as growth recommences, whereas if the cut is too close the bud is starved, or if less close an ugly and awkward snag is left." — Encyclopedia Britannica, 1893

Pruning

"The nature of the cut itself in pruning is of more consequence, especially in the case of fruit trees,…

"The nature of the cut itself in pruning is of more consequence, especially in the case of fruit trees, than at first signt may appear. The branches should be separated by a clean cut at an angle of abouot 45 degrees, just at the back of a bud, the cut entering on a level with the base of the bud and passing out on a level with its top, for when cut in this way the wound becomes rapidly covered with new wood, as soon as growth recommences, whereas if the cut is too close the bud is starved, or if less close an ugly and awkward snag is left." — Encyclopedia Britannica, 1893

Pruning

"The nature of the cut itself in pruning is of more consequence, especially in the case of fruit trees,…

"The nature of the cut itself in pruning is of more consequence, especially in the case of fruit trees, than at first signt may appear. The branches should be separated by a clean cut at an angle of abouot 45 degrees, just at the back of a bud, the cut entering on a level with the base of the bud and passing out on a level with its top, for when cut in this way the wound becomes rapidly covered with new wood, as soon as growth recommences, whereas if the cut is too close the bud is starved, or if less close an ugly and awkward snag is left." — Encyclopedia Britannica, 1893

Pruning

"The nature of the cut itself in pruning is of more consequence, especially in the case of fruit trees,…

"The nature of the cut itself in pruning is of more consequence, especially in the case of fruit trees, than at first signt may appear. The branches should be separated by a clean cut at an angle of abouot 45 degrees, just at the back of a bud, the cut entering on a level with the base of the bud and passing out on a level with its top, for when cut in this way the wound becomes rapidly covered with new wood, as soon as growth recommences, whereas if the cut is too close the bud is starved, or if less close an ugly and awkward snag is left." — Encyclopedia Britannica, 1893

Pruning

"The nature of the cut itself in pruning is of more consequence, especially in the case of fruit trees,…

"The nature of the cut itself in pruning is of more consequence, especially in the case of fruit trees, than at first signt may appear. The branches should be separated by a clean cut at an angle of abouot 45 degrees, just at the back of a bud, the cut entering on a level with the base of the bud and passing out on a level with its top, for when cut in this way the wound becomes rapidly covered with new wood, as soon as growth recommences, whereas if the cut is too close the bud is starved, or if less close an ugly and awkward snag is left." — Encyclopedia Britannica, 1893

Pruning

"The nature of the cut itself in pruning is of more consequence, especially in the case of fruit trees,…

"The Montreuil form of training. The principal feature is the suppression of the direct channel of the sap, and the substitution of for or more commonly two mother branches, so laid to the wall that the central angle contains about 90 degrees. The other branches are all treated as subordinate members. This form is open to the objection that, if the under branch should die, the upper one cannot be brought down into its place." — Encyclopedia Britannica, 1893

Montreuil Fan

"The Montreuil form of training. The principal feature is the suppression of the direct channel of the…

"Professor James Thomson's inward flow or vortex turbine has been selected as the type of reaction turbines. It is one of the best even in normal conditions of working, and the mode of regulation introduced is decidedly superior to that in most reaction turbines; it might almost be said to be the only mode of regulation which satisfies the conditions of efficient working, and it has been adopted in a modified form in the Leffel turbine, which is now largely used in america. The turbine has suction pipes, which permit the turbine to be placed at any height less than 30 feet above the tail-water level. The water enters the turbine by cast-iron supply pipes at A, and is discharged through two suction pipes S. The water on entering the case distributes itself through a rectangular supply chamber SC, from which it finds its way equally to the four guide-blade passages G. In these passages it acquires a velocity about equal to that due to half the fall, and is directed into the wheel at an angle of about 10 or 12 degrees with the tangent to its circumference. The wheel W receives the water in equal proportions from each guide-blade passage." — Encyclopedia Britannica, 1893

Reaction Turbine

"Professor James Thomson's inward flow or vortex turbine has been selected as the type of reaction turbines.…

"Professor James Thomson's inward flow or vortex turbine has been selected as the type of reaction turbines. It is one of the best even in normal conditions of working, and the mode of regulation introduced is decidedly superior to that in most reaction turbines; it might almost be said to be the only mode of regulation which satisfies the conditions of efficient working, and it has been adopted in a modified form in the Leffel turbine, which is now largely used in america. The turbine has suction pipes, which permit the turbine to be placed at any height less than 30 feet above the tail-water level. The water enters the turbine by cast-iron supply pipes at A, and is discharged through two suction pipes S. The water on entering the case distributes itself through a rectangular supply chamber SC, from which it finds its way equally to the four guide-blade passages G. In these passages it acquires a velocity about equal to that due to half the fall, and is directed into the wheel at an angle of about 10 or 12 degrees with the tangent to its circumference. The wheel W receives the water in equal proportions from each guide-blade passage." — Encyclopedia Britannica, 1893

Reaction Turbine

"Professor James Thomson's inward flow or vortex turbine has been selected as the type of reaction turbines.…

"Professor James Thomson's inward flow or vortex turbine has been selected as the type of reaction turbines. It is one of the best even in normal conditions of working, and the mode of regulation introduced is decidedly superior to that in most reaction turbines; it might almost be said to be the only mode of regulation which satisfies the conditions of efficient working, and it has been adopted in a modified form in the Leffel turbine, which is now largely used in america. The turbine has suction pipes, which permit the turbine to be placed at any height less than 30 feet above the tail-water level. The water enters the turbine by cast-iron supply pipes at A, and is discharged through two suction pipes S. The water on entering the case distributes itself through a rectangular supply chamber SC, from which it finds its way equally to the four guide-blade passages G. In these passages it acquires a velocity about equal to that due to half the fall, and is directed into the wheel at an angle of about 10 or 12 degrees with the tangent to its circumference. The wheel W receives the water in equal proportions from each guide-blade passage." — Encyclopedia Britannica, 1893

Reaction Turbine

"Professor James Thomson's inward flow or vortex turbine has been selected as the type of reaction turbines.…

"Professor James Thomson's inward flow or vortex turbine has been selected as the type of reaction turbines. It is one of the best even in normal conditions of working, and the mode of regulation introduced is decidedly superior to that in most reaction turbines; it might almost be said to be the only mode of regulation which satisfies the conditions of efficient working, and it has been adopted in a modified form in the Leffel turbine, which is now largely used in america. The turbine has suction pipes, which permit the turbine to be placed at any height less than 30 feet above the tail-water level. The water enters the turbine by cast-iron supply pipes at A, and is discharged through two suction pipes S. The water on entering the case distributes itself through a rectangular supply chamber SC, from which it finds its way equally to the four guide-blade passages G. In these passages it acquires a velocity about equal to that due to half the fall, and is directed into the wheel at an angle of about 10 or 12 degrees with the tangent to its circumference. The wheel W receives the water in equal proportions from each guide-blade passage." — Encyclopedia Britannica, 1893

Reaction Turbine

"Professor James Thomson's inward flow or vortex turbine has been selected as the type of reaction turbines.…

"A very beautiful American, bird, found in all parts of the United States, and as far north as 55 degrees N. lat., but migrating to tropical or subtropical regions in winter." — Chambers' Encyclopedia, 1875

Oriole

"A very beautiful American, bird, found in all parts of the United States, and as far north as 55 degrees…

"Crown-work, in Fortification, is formed to strengthen a weak front, or to occupy ground which might facilitate the enemy's operations. It consists of two faces inclined to each other at an angle, with a bastion in the middle, and half-bastions at the two ends; and it is connected with the main body of the work by two long sides. RMNPS is the crown-work, in front of and protecting the ravelin O. Both of these works are entirely beyong the main ditch of the place, but each has also a ditch of its own." — Chambers' Encyclopedia, 1875

Crown-Work

"Crown-work, in Fortification, is formed to strengthen a weak front, or to occupy ground which might…

"Upon a tripod provided with levelling screws stands the pillar P, to which is fixed the graduated azimuthal circle CC. The compass box B, with the vernier V, attached to it, moves on the azimuthal circle by means of a pivot at the pillar P. Two uprights, U, U, are fixed to the side of the compass-box, on the tops of which rests the axis of the telescope T. A graduated are A, is fixed to the bottom of one of the uprights, and the angle of elevation of the telescope is marked by the vernier on the arm E, attached to the axis of the telescope. A level, L, is also hung on the axis of the telescope, for adjusting the instrument. Inside the compass-box is another graduated circle, F, the line joining the zero-points of which is parallel to the axis of the telescope. All the fittings are in brass or copper, iron, of course, being unsuitable." — Chambers' Encyclopedia, 1875

Declinometer

"Upon a tripod provided with levelling screws stands the pillar P, to which is fixed the graduated azimuthal…

"The usual form of crank-axle bearing which has inward-cups and is cup-adjusting. The end of the bracket is split and the cup after adjustment is clamped in position by the clamping screw S. The usual mode of fastening the cranks to the axle is by round cotters C with a flat surface at a slight angle to the axis, thus forming a wedge, which is driven in tight. The small end of the cotter projects through the crank, and is screwed and held in place by a nut. The chain-wheel at the crank-axis is usually detachable fastened to the right-hand crank." — The Encyclopedia Britannica, 1910

Crank-axle Bearing

"The usual form of crank-axle bearing which has inward-cups and is cup-adjusting. The end of the bracket…

"An optical instrument employed to facilitate the sketching of objects from nature by producing a reflected picture of them upon paper. Wollaston's apparatus is one of the commonest. The essential part is a totally-reflecting prism with four angles, one of which is 90 degrees, the opposite one 135 degrees, and the other two each 67 degrees. One of the two faces which contain the right angle is turned towards the object to be sketched." — Winston's Encyclopedia, 1919

Camera Lucida

"An optical instrument employed to facilitate the sketching of objects from nature by producing a reflected…

"The root used in medicine under this name is obtained from Cephaelis Ipecacuanha, A. Rich, a small shrubby plant of the natural order Cinchonaceae. It is a native of Brazil, growing in clumps or patches in moist shady forests from 8 degrees to 22 degrees S. lat., and is believed to extend to the Bolivian province of Chiquitos, and the calley of Catica in New Granada." — The Encyclopedia Britannica, 1893

Ipecacuanha Plant

"The root used in medicine under this name is obtained from Cephaelis Ipecacuanha, A. Rich, a small…

"Another form is called the polyangular kaleidoscope. The only essential difference in it is that the mirrors are so arranged that the angle between them can be varied at pleasure. This, being very useful for illustrating the theory of the instrument, is the form usually found in collections of philosophical apparatus." —The Encyclopedia Britannica, 1910

Polyangular Kaleidoscope

"Another form is called the polyangular kaleidoscope. The only essential difference in it is that the…

"In the ordinary pattern of a lapidary's bench the handle turns in a horizontal plane, where W is the driving-wheel turned by the handle A, and working the pulley P by means of a strap. The pulley is fixed on a vertical spindle, which carries M the disk for slitting or the leaden lap for roughing or polishing. The upper end of this spindle is conical, and rotates in a socket drilled in a horizontal arm of iron which projects from a vertical wooden rod D. A block of wood C fits on to the end of an iron support termed the gim-peg or germ-peg. This support is used to steady the operator's arm when grinding the edges of small stones, and the wooden block, which is fixed by a wedge, is employed for cutting facets at any desired angle, the stone being cemented to the end of a stik S, which is fixed at the requisite angle in one of the holes or notches made in the sides of the socket C." —The Encyclopedia Britannica, 1910

Lapidary's Mill

"In the ordinary pattern of a lapidary's bench the handle turns in a horizontal plane, where W is the…

"In order to produce, on the catoptric system, a fixed light showing all round the circle, a number of reflectors are fixed round the outside of a stationary chandelier n. As the ordinary paraboloid has about 14 degrees of divergence, twenty-five reflectors were needed to light up continuously (though not equally) the whole horizon." —The Encyclopedia Britannica, 1910

Revolving Light

"In order to produce, on the catoptric system, a fixed light showing all round the circle, a number…

"Fresnel next conceived the admirable improvement of employing the principle of "total" or internal reflexion by glass prisms. The ray Fi falling on a prismoidal ring, ABC, is refracted and bent in the direction iR, and falling on the side AC, at an angle of incidence greater than the critical, is totally relfected in the direction Re, and, impinging on the side BC at e, it undergoes a second refraction, and emerges horizontally. The highest ray FA after refraction by AB and reflexion by AC must (in order to avoid superfluous glass) pass along AB, and after a second refraction at B emerge horizontally. The lowest ray FB after refraction by AC and a second refraction by BC also emerge horizontally." —The Encyclopedia Britannica, 1910

Reflecting Prism

"Fresnel next conceived the admirable improvement of employing the principle of "total" or internal…

"Perfect Form of Dioptric Holophote for an Oil Flame.—By combining the back prisms ga, hc just described with a semi-holophote abc subtending 180 degrees and a portion of the dioptric spherical mirror ijk, no light is lost on the burner, and all the rays are parallelized, so that this apparatus, being all of glass, is both geometrically and physically perfect." —The Encyclopedia Britannica, 1910

Dioptric Holophote

"Perfect Form of Dioptric Holophote for an Oil Flame.—By combining the back prisms ga, hc just described…

"Professor Swan's Designs.—Among several ingenious arrangements and new forms of agents proposed by Professor Swan is the mode of sending rays from prisms through interstices left between other prisms placed in front, and also a form of agent which he termed the triesoptric prism, in which the rays would undergo two refractions and three reflexions. a are the front and b the triesoptric prisms. The two upper and lower prisms a are constructed of flint glass of high refractive power. It will be observed from the drawing that this ingenious arrangement is nevertheless open to objection, for cones of light of 30 degrees in front and of 65 degrees at the back are lost through the interstices." —The Encyclopedia Britannica, 1910

Swans Designs

"Professor Swan's Designs.—Among several ingenious arrangements and new forms of agents proposed by…

"Differential Lens.—Horizontal divergence may be obtained to any required amount by varying the radius of curvature of the inner face of an annular lens. The outer face is the same as that of an ordinary annular lens, which the other face, though straight in the vertical, is ground to the required curve in the horizontal plane. The rays f'fc falling upon the lens x converge to the vertical focal plane ff and afterwards diverge through the smaller horizontal angle x'f'x', and so for any other case." —The Encyclopedia Britannica, 1910

Differential Lens

"Differential Lens.—Horizontal divergence may be obtained to any required amount by varying the radius…

"Differential Lens.—Horizontal divergence may be obtained to any required amount by varying the radius of curvature of the inner face of an annular lens. The outer face is the same as that of an ordinary annular lens, which the other face, though straight in the vertical, is ground to the required curve in the horizontal plane. The rays f'fc falling upon the lens x converge to the vertical focal plane ff and afterwards diverge through the smaller horizontal angle x'f'x', and so for any other case." —The Encyclopedia Britannica, 1910

Differential Lens

"Differential Lens.—Horizontal divergence may be obtained to any required amount by varying the radius…

"Differential Lens.—Horizontal divergence may be obtained to any required amount by varying the radius of curvature of the inner face of an annular lens. The outer face is the same as that of an ordinary annular lens, which the other face, though straight in the vertical, is ground to the required curve in the horizontal plane. The rays f'fc falling upon the lens x converge to the vertical focal plane ff and afterwards diverge through the smaller horizontal angle x'f'x', and so for any other case." —The Encyclopedia Britannica, 1910

Differential Lens

"Differential Lens.—Horizontal divergence may be obtained to any required amount by varying the radius…

"Condensing Apparatus for Steamer's Side Lights.—By means of this application of the condensing principle all the light can be distributed with strict equality over 112 degrees, which is the arc prescribed for steamers by the Board of Trade. Several of the Transatlantic and other steamers have adopted this kind of apparatus, which is hung on gimbals and placed in iron towers, having an entry from below the deck, which can be made use of in bad weather." —The Encyclopedia Britannica, 1910

Condensing Apparatus

"Condensing Apparatus for Steamer's Side Lights.—By means of this application of the condensing…

"Condensing Apparatus for Steamer's Side Lights.—By means of this application of the condensing principle all the light can be distributed with strict equality over 112 degrees, which is the arc prescribed for steamers by the Board of Trade. Several of the Transatlantic and other steamers have adopted this kind of apparatus, which is hung on gimbals and placed in iron towers, having an entry from below the deck, which can be made use of in bad weather." —The Encyclopedia Britannica, 1910

Condensing Apparatus

"Condensing Apparatus for Steamer's Side Lights.—By means of this application of the condensing principle…

"Condensing Quadrant.—The fixed apparatus bbb, with spherical mirror behind, throws its rays directly through the angle of 90 degrees afa', while the supplementary rays falling on the straight condensing prisms p, p, p', p' are sent out parallel to the corresponding rays in the unobstructed central quadrant of the main apparatus. The whole light will therefore be condensed equally over 90 degrees." —The Encyclopedia Britannica, 1910

Condensing Quadrant

"Condensing Quadrant.—The fixed apparatus bbb, with spherical mirror behind, throws its rays directly…

"Condensing Octant.—The central fixed apparatus bb with spherical mirror dd throws its rays directly over the angle of 45 degrees pgp, while the supplemental rays fall upon the straight condensing prisms p, each of which spreads the incident rays parallel to the corresponding rays in the central angle pgp. In this way the whole of the front hemisphere of rays is parallelized in the vertical plane and spread equally over the 45 degree in azimuth." —The Encyclopedia Britannica, 1910

Condensing Octant

"Condensing Octant.—The central fixed apparatus bb with spherical mirror dd throws its rays directly…

"Condensing Octant.—The central fixed apparatus bb with spherical mirror dd throws its rays directly over the angle of 45 degrees pgp, while the supplemental rays fall upon the straight condensing prisms p, each of which spreads the incident rays parallel to the corresponding rays in the central angle pgp. In this way the whole of the front hemisphere of rays is parallelized in the vertical plane and spread equally over the 45 degree in azimuth." —The Encyclopedia Britannica, 1910

Condensing Octant

"Condensing Octant.—The central fixed apparatus bb with spherical mirror dd throws its rays directly…

"Suppose the Earth to be in her Summer solstice, which takes place on the 21st of June. At this period she will be at a, having her north pole, n, so inclined towards the Sun, that the whole arctic circle will be illuminated, and consequently the Sun's rays will extend 23.25 degrees, the breadth of the polar circle, beyond the north pole." —Comstock, 1850

Seasons

"Suppose the Earth to be in her Summer solstice, which takes place on the 21st of June. At this period…

"Let S be the Sun, E the Earth, and A, B, C, D, F, the Moon in different parts of her orbit. Now when the Moon changes, or is in conjunction with the Sun, as at A, her dark side is turned towards the Earth, and she is invisible, as represented at a. The Sun always shines on one half of the Moon, in every direction, as represented at A and B, on the inner circle; but we at the Earth can see only such portions of the enlightened part as are turned towards us. After her change, when she has moved from A to B, a small part of her illuminated side comes in sight, and she appears horned, as at b, and is then called the new Moon. When she arrives at C, severel days afterwards, one half of her disc is visible, and she appears as at c, her appearance being the same in both circles. At this point she is said to be in her first quarter, because she has passed through a quarter of her orbit, and is 90 degrees from the place of her conjunction with the Sun. At D, she shows us still more of her enlightened side, and is then said to appear gibbous as at d. When she comes to F, her whole enlightened side is turned towards the Earth, and she appears in all the spendor of a full Moon." —Comstock, 1850

Moon Phases

"Let S be the Sun, E the Earth, and A, B, C, D, F, the Moon in different parts of her orbit. Now when…

"The middle one an ordinary hook tool, suited for outside work on wrought iron or steel, and the one above it a left hand tool which can be used also for inside. Their cutting edges are of course forged and ground straighter or more pointed or otherwise varied according to circumstances, and for cast iron or brass the angle of the edge is made much less acute, as in the lowest of the three in the engaving." —The Encyclopedia Britannica, 1903

Slide-Rest Tools

"The middle one an ordinary hook tool, suited for outside work on wrought iron or steel, and the one…

"Longitudinal and Vertical section of the skull of a dog, with mandible and hyoid arch. an, anterior narial aperture; MT, maxillo-turbinal bone; ET, the ethmo-turbinal; Fr, frontal; Pa, pariental; IP, interparietal; SO, supra-occipital; ExO, sphenoid; OS, orbito-sphenoid; PS, presphenoid; Pl, palatine; Vo, vomer; Mx, maxilla; PMx, premaxilla; sh, stylo-hyal; eh, epi-hyal; ch, cerato-hyal; bh, basihyal; th, thyro-hyal; s, symphysis of mandible; cp, coronoid process; cd, condyle; a, angle; id, inferior dental canal. The mandible is displaced downwards, to show its entire form; the * indicated the part of the cranium to which the condyle is articulated." —The Encyclopedia Britannica, 1903

Dog Skull

"Longitudinal and Vertical section of the skull of a dog, with mandible and hyoid arch. an, anterior…

"The original Merz micrometer of the Cape Observatory, made on Fraunhofer's model. S is the head of the micrometer screw proper, s that of the screw moving the slide to which the so-called "fixed web" is attached, s' that of a screw which moves the eye-piece E. C is the clamp and M the slow motion in position angle, L, L are tubes attached to a larger tube N; the latter fits loosely on a strong hollow cylinder which terminates in the screw V. By this screw the whole apparatus is attached to the telescope." —The Encyclopedia Britannica, 1903

Micrometer

"The original Merz micrometer of the Cape Observatory, made on Fraunhofer's model. S is the head of…

"a is the sphere, placed in half-holes on the axis bb, so that when its principal axis is parallel to the axis the telescope it gives only one image of the object. In a direction perpendicular to that axis it must be so placed that when it is moved by rotation of the axis bb the separation of the images shall be parallel to that motion. The angle of rotation is measured on the grduated circle C. The angle between the objects measured is = r sin 20, where r is a constant to be determined for each magnifying power employed." —The Encyclopedia Britannica, 1903

Micrometer

"a is the sphere, placed in half-holes on the axis bb, so that when its principal axis is parallel to…

"a is the sphere, placed in half-holes on the axis bb, so that when its principal axis is parallel to the axis the telescope it gives only one image of the object. In a direction perpendicular to that axis it must be so placed that when it is moved by rotation of the axis bb the separation of the images shall be parallel to that motion. The angle of rotation is measured on the grduated circle C. The angle between the objects measured is = r sin 20, where r is a constant to be determined for each magnifying power employed." —The Encyclopedia Britannica, 1903

Micrometer

"a is the sphere, placed in half-holes on the axis bb, so that when its principal axis is parallel to…

"The circles for position angle and declination are read by micrometer microscopes illuminated by the lamp L; the scales are illuminated by the lamp l. T is part of the tube proper and turns with the head. The tube V, on the contrary, is attached to the cradle, and merely forms a support for the finder Q, the handles at f and p, and the moving ring P. The latter gives quick motion in position angle; the handles a p clamp and give slow motion in position angle, those at f clamp and give slow motion in right ascension and declination." —The Encyclopedia Britannica, 1903

Micrometer

"The circles for position angle and declination are read by micrometer microscopes illuminated by the…

Still life arrangement including a globe, telescope, book, right angle, rolled map, and dividers.

Still Life with Globe and Telescope

Still life arrangement including a globe, telescope, book, right angle, rolled map, and dividers.

If the earth were uniformly covered with a layer of water, the passage of the moon over any place as at <em>a</em>, would cause the water to lose its globular form, become bulged at <em>a</em>, and <em>b</em>, and flattened at <em>c</em>, and <em>d</em>. In other words, the water would become <em>deeper</em> at <em>a</em>, and <em>b</em>, at the parts of the earth nearest and farthest from the moon and <em>shallower</em> in all places 90 degrees or at right angles to these points.

Lunar Tide

If the earth were uniformly covered with a layer of water, the passage of the moon over any place as…