Miscellaneous. 
BURNING GLASSES, 
A remarkably large parabolic lens was recently purchased at 
Vienna, for the French government. It was made at Gratz, in 
Styria, by Rospine, a celebrated mechanist, for some alchemist. It 
was not cast, but softened by heat and bent over a parabolic mould* 
Several pieces were broken before he succeeded ; so that it cost 
originally from 800 to 1200 guineas. It is three feet three inches 
in diameter, and of eight feet four inches focus ; composed of 2 
pieces of glass united together by an iron hoop so as to form a hol- 
low vessel, capable of holding eighty or ninety quarts of spirits of 
wine. M. Jacquin, of Vienna, and several men of science, who 
witnessed the experiments, declared, that it burned a diamond in a 
few seconds, and fused platina in a few minutes. A button of pla- 
tina weighing twenty-nine grains, was melted by it, and made in 
part to boil. The diameter of the focus does not appear to exceed 
four lines. It weighs 550lbs. avoirdupois. London Pap. 
This seems to me to be an improvement in the manufacture of 
lenses. 
Of burning glasses. I have examined the question concern- 
ing the burning glasses of Archimedes. It rests upon vague and 
second hand authority. Polybius says nothing of it : nor Livy* 
nor Plutarch. There is not authority sufficient for the story of the 
burning glasses of Proclus. Such feats may have been done * 
there is no clear testimony to warrant our assertion that they were 
done. 
In modern times, the glasses of Villette, Tchirnhausen, Buf- 
fon, Trudaine, and Parker are well known. That of M. Trudaine 
made at the expence of 1000/. sterling and presented by him to the 
Academy of sciences was constructed somewhat on the principle 
of the above mentioned lens. Two concave glasses, joined by 
their edges so as to present a cavity of 4 feet diameter, filled with 
140 French pints of spirit of wine. It was broken by accident soon 
after it was presented. In the glass above mentioned made at Vi- 
enna, the improvement seems to be, the bending the plane glasses 
by gradual heat, over the mould. 
Parker’s lens, made at the expence of 700/. sterling, was sold 
by him for less than prime cost, and carried out by Lord Macart- 
ney as a present to the emperor of China, to be placed among the 
toys of that childish court. This was clearly the best lens ever 
constructed ; and it is a disgrace to the nation, that Mr, Parker 
