M. TECHNOLOGY. 555 



iron and steel, it appears not to apply to glass. By the ap- 

 plication of heat in the form of a tempering bath, however, 

 he succeeded in effecting his purpose, and in changing the 

 physical properties of this material to a remarkable degree. 



That the invention is attracting considerable notice will be 

 manifest from the following comments of the London Times of 

 recent issue : " Of the practical value of M. De la Bastie's dis- 

 covery there can be no question whatever; nor can there be 

 any doubt of its value in the arts, sciences, and manufactures. 

 The applications which suggest themselves are innumerable ; 

 and above and beyond the utility of the process in relation 

 to articles of domestic use, come important considerations 

 affecting the applied sciences, especially in connection with 

 chemical manufactures and similar industries, where a ma- 

 terial equally indifferent to the action of heat and acids has 

 been long and vainly sought for notably in connection with 

 the vitriol chambers in the manufacture of sulphuric acid, 

 and for piping in chemical works." 



The technical journals give at considerable length the de- 

 tails of a number of comparative tests of the strength of the 

 Bastie product and of ordinary glass, which appear to be well 

 authenticated. These accounts all acn-ee in the statement 



CD 



that the tempered glass possesses, in comparison with the or- 

 dinary glass, an astonishing degree of toughness, whether sub- 

 jected to the test of rapid alternations of heat and cold or the 

 impact of a falling weight. The following comparative ex- 

 periment, selected from a number, will serve our purpose. A 

 piece of ordinary plate-glass is reported to have been broken 

 by a 2-ounce brass weight falling from a height of 24 inches. 

 On a thinner piece of toughened glass no impression was made 

 by the same weight falling from heights ranging from 2 feet 

 to 10 feet, the weight simply rebounding from the glass. An 

 8-ounce weight, tried at 2 feet and 4 feet, gave with the same 

 piece a similar result. At 6 feet, however, the glass broke. 

 The breaking of the plates under these circumstances appears 

 to be attended with the same phenomenon of complete dis- 

 integration that characterizes the well-known scientific toy 

 known as Prince Rupert's drop a coincidence that may be 

 of value in explaining the nature of the change of qualities 

 effected by the Bastie process. 



