SCIENTIFIC SUMMARY. 
331 
Toughening Glass . — The important discovery of M. de la Bastie is ex- 
plained very fully in a paper Tby Mr. P. F. Nursey in our present number. In 
the course of Mr. Nursey’s experiments before the Society of Arts, some 
glass dessert-plates were dropped from a height of between four and five feet 
to the ground without fracture, one of them rebounding over a table. Sub- 
sequently one of the audience dropped a plate from a height of four feet on 
to an iron grating, and it rebounded to the height of a foot without injury.. 
Grease-catchers, to put on candles, were thrown with some force from the 
same height with similar result, except when four were thrown together, 
and then one of them broke into innumerable fragments, without the sharp 
cutting edges which are so characteristic of the fracture of glass not so 
toughened. A piece of plate glass about six inches square and a quarter- 
inch thick was next put into a frame of wood, so as to raise the under sur- 
face of the glass half an inch from the floor. A brass 4-oz. weight was then 
dropped several times from a height of ten feet fairly on to the centre of the 
piece of glass with perfect impunity. Next an 8-oz. weight was tried with 
the same result. Then a piece of ^-inch plate was substituted, and the 
lecturer, a man approaching 12 stone in weight, put his heel in the centre 
and spun round on it. Next the 8-oz. weight was dropped on it, and, as in 
the case of the thicker piece, without the slightest damage. A piece of the 
same quarter-inch plate glass, which had not been toughened, was broken 
with the usual star fracture by dropping the 4-oz. weight from a height of 
two feet. At last, as it seemed impossible to break the plates of glass in 
any other way, a hammer was brought, and a smart blow being given to one 
of the quarter-inch thick plates, it shivered into a great number of very small 
pieces, and with the peculiarity of the edges of the pieces being rounded, as 
if partially fused after fracture. 
Mr. Crookes' Discovery ; the Mechanical Power of Light . — On this very im- 
portant subject the discoverer has already contributed two papers (the second 
on April 27) to the Royal Society. In these, as in his especially beautiful 
and elaborate experiments, conducted at the Royal Society’s soiree, Mr. 
Crookes has, we think, proved that light alone — all heat being absorbed — is 
sufficient to produce mechanical force. Professor 0. Reynolds has attempted 
an explanation of the action, supposing it to be due to evaporation and con- 
densation at the surface, but his efforts have been shown to be idle. Mr. 
Crookes philosophically concludes with the following remarks : — While ob- 
jecting to the theories already advanced as not accounting for all the facts of 
the case, the author confesses that he is not as yet prepared with one to put 
in their place. He wishes to avoid giving any theory on the subject until a 
sufficient number of facts have been accumulated. The facts will then tell 
their own tale. The conditions under which they invariably occur will givo 
the laws, and the theory will follow without much difficulty. 
