96 Answers to Queries. 
entire surface. Set aside the plate to cool. The design to be 
put upon the glass should be drawn boldly in very black ink upon 
a piece of paper, and attached to the unwaxed side of the glass. 
The pattern is then traced through the wax with a pointed 
instrument, taking care to clear away all the wax in the lines. 
When the design is finished, put some coarsely powdered fluor 
spar in a vessel, together with a quantity of sulphuric acid. As 
soon as they are incorporated, the vessel is slightly heated, and the 
glass placed over the vessel with the waxed side down. When the 
fumes of the acid begin to rise, they attack the unprotected sur- 
face of the glass, and in about half an hour the plate can generally 
be removed from its steam-bath. When the wax is scraped off, 
the design will be found perfectly etched on its surface. Bab: 
338.—Soap-Bubbles.—A reference to Vol. VIII., p. 358, of 
the Lntellectual Observer will supply what information you seek 
under the title of “New Experiments with Soap-Bubbles,” by 
John Broughton, B.Sc. The solution recommended is as follows : 
—‘ Dissolve one part of pure oleate of soda in fifty parts of 
distilled water, and to every three volumes of the clear solution 
thus formed mix two volumes of pure glycerine.” The bubbles 
formed from this mixture will endure in a pure atmosphere from 
one hour and a-half to four hours, and occasionally much longer, 
but they then require to be shielded from draughts. ‘The perma- 
nence of these bubbles depends upon the purity of the oleate of 
soda, which is rather troublesome to prepare. I can endorse the 
accuracy of the above, having myself prepared the mixture 
successfully. A more easy method, but not so successful, is to 
take 150 grains of finely-shred Castille soap, and shake it up in a 
bottle with half-a-pint of distilled water until dissolved ; allow the 
turbid solution to settle and filter through blotting-paper. Use the 
clear solution to mix with glycerine instead of that of the pure 
oleate. E. Bosrock. 
338.—Soap Bubbles.—I find the following in my book of 
miscellaneous cuttings, but cannot give the authority :—(r1) 
Dissolve 1 part, by weight, of Marseilles soap cut into thin slices 
in 40 parts of distilled water, and filter. Call this filtered liquid 
A. (2) Mix 2 parts, by measure, of pure glycerine with 1 part of 
solution A in a temperature of 66° Fahr., and after shaking them 
together long and violently, leave them to rest for some days. <A 
clear liquid will settle with a turpid one above. The lower is to 
be sucked out from beneath the upper with a siphon, taking the 
utmost care not to carry down any of the latter to mix with the 
clear fluid. M.E. 
agit 
