ClipArt ETC
"The parting vessels are of porcelain which, to protect them against fracture by irregular heating, are covered with wire netting and plastered over with a mixture of clay and smithy scales. They are mounted in a frame and set loose in an iron pot with a hemispherical bottom, which is heated by a fire from below, the pot also serves to catch the contents of the porcelain vessel if the latter should be accidentally broken. The cover is perforated by a hole in the center for the passage of a lead pipe to carry off the sulphurous acid fumes." — Encyclopedia Britannica, 1893

Parting Vessel

"The parting vessels are of porcelain which, to protect them against fracture by irregular heating,…