1875.| Physics. 409 
slightest degree, even when applied while the material was in a fluid or soft 
condition. He therefore changed his tactics, and commenced to apply to 
glass a system of tempering, such as is usually applied to steel, namely, sub- 
mitting it to a bath of heated oil. jHe knew well that by immersing heated 
glass in cold water he would only put the material in a state of unstable 
equilibrium, so that the least shock would cause it to break up, as in the case 
of the Rupert drops. He then sought to invert this result, to diminish, or 
even to remove, the extreme fragility of glass by tempering it by immersion 
in a fluid other than water. In attaining this obje@ two essential objects 
had to be determined. First, the point at which glass can be tempered 
without being put out of shape, and secondly, the medium to be employed for 
the immersion of the glass. The first condition M. de la Bastie found to be 
that degree of heating at which softness or malleability commences, when 
the molecules are capable of closing suddenly together, condensing the 
material when it is plunged in a liquid at a somewhat lower temperature. 
The second condition he found was satisfied by having a fluid capable of 
being raised to a much higher temperature than that of boiling water, 
without entering into a state of ebullition. For this purpose, and after a long 
series of experiments, M. de la Bastie devised an oleaginous compound, 
formed of oils, wax, tallow, resin, and other similar ingredients in certain 
proportions. Although the invention is apparently a most simple one, there 
are many delicate conditions involved, the disregard of any one of which con- 
stitutes the precise difference between success and failure. It thus happened 
that, seven years since, just as M. de la Bastie had perfected his invention, 
and had produced highly satisfactory results, he lost the clue to his success, 
and for two years was baffled in every attempt to re-discover it. He at 
length succeeded in regaining his secret, and has since been engaged in 
perfecting his invention, and putting it into a practical shape. He had to 
carefully adjust all the numerous details, for although the invention consists 
in simply heating the glass, and dipping it while hot into a heaced oleaginous 
bath, there are many conditions involved. Thus glass articles may be under- 
heated, and will not be susceptible to the effect of the bath, or they may be 
overheated, and will lose their shape; or, again, they may be heated to the 
right temperature, and yet be spoiled during the process of transference into 
the bath. Then, again, the exact proportions of the oleaginous constituents 
of the bath, and their precise temperature, have an important influence upon 
the ultimate result. All these points, however, with many others, have been 
definitely settled by M. de la Bastie, who has for some time past worked his 
process experimentally, and is now erecting a factory in France, in which to 
carry it on practically and commercially. It may be as well that I should 
here mention that it is recorded by Pliny, that in the reign of Tiberius a com- 
bination was said to have been devised by which a flexible glass was produced, 
and that the machinery by which it was made was destroyed in order to 
prevent a depreciaticn in the value of the precious metals. We have, how- 
ever, no evidence that this was the toughening process invented by M. de la 
Bastie, and the statement to which publicity has recently been given, in no 
whit detracts from the merits of that gentleman as the inventor of an 
important economic process. Nothing more than the bare fact above alluded 
to is on record, except it be, perhaps, that the hapless inventor was destroyed 
as well as his apparatus. But there was no Society for the Encouragement 
of Arts, Manufactures, and Commerce in those days. In carrying out his 
process, M. de la Bastie finds it necessary to raise the glass to be tempered to 
a very high temperature. The hotter it is the less the risk of breaking the 
glass, and the greater the shrinkage or condensation. Hence the advantage, 
and often the necessity, of heating the glass to the point of softening, which 
is attended by the difficulty that glass in the soft condition gets readily out of 
shape, so that it must be plunged into the bath almost without touching it. 
In plunging the hot glass into a heated combustible liquid the latter is apt to 
take fire, and cannot easily be extinguished, so that time and material are 
lost. These difficulties M. de la Bastie has overcome by placing the temper- 
ing bath in immediate communication with the heating oven, and covering it 
