ETCHING ON GLASS—GLASS-CUTTING. 245

animals and plants, in a manner perfectly natural, andbrought them to the highest perfection.

The glass proposed to be etched is made perfectlyfree from grease and clean, then the figure is coveredwith a varnish, then an edge of wax being raised roundthe glass, the acid is poured in, and the whole ground onthe exterior of the figure appears rough, whilst the figureis preserved in its original beauty of outline, bright andsmooth. This is the mode the inventor adopted.

Professor Beckmann says, he mentioned this ancientmethod of etching upon glass to an artist of the name ofKlindworth, who possessed great dexterity in such arts,and requested him to try it; he drew a tree with oil varnishand colours, on a plate of glass, applied the acid on theplate in the usual manner ; after it had been upon the platefor a sufficient time, poured off, and the plate afterwardscleaned of the varnish; a beautiful tree was left brightand smooth, with a rough back ground. It is conceivedthat many great improvements may be yet made in thisprocess.

It appears that no other kind of acid than that producedby the sparry fluor is capable of corroding every kind of glass,though Baume, in his Experimental Chemie, iii. p. 302,says that many kinds of glass may be corroded by themarine and vitriolic acids.

In this state of uncertainty was the public mind till theyear 1725, when it was thought that a recipe older thanthat previously mentioned might possibly be discovered.Accordingly, in that year, in the month of January, in the(Ekonomische Encyclopedic, xi. p. 678; the followingis said to be transmitted to the publisher by Dr. John GeorgeWeygand, of Goldingen , which is reported to have be-longed to Dr. Matth. Pauli, of Dresden , then deceased,with which the last named gentleman had etched on glass,arms, landscapes, and figures of various kinds. We findthat in it strong acid of nitre was used, which entirelydisengages the acid of sparry fluor, though the vitriolicacid has been commonly employed, and figures thus pro-duced will appear as if raised above the plane of the glass.

This sparry fluor is found among Derbyshire productionsas well as in the mines of Germany. Theophrastus is the first who notices the effect of sparry fluor, by observing, that thereare certain stones which, when added to silver, copper, andiron ores, become fluid. It appears that Cronstedt wasthe first systematic writer who gave it a name.

When spiritus nitri per distillationem has passed into the