Foreign Literature and Science. 305. 
charged with from two to three pounds of powder. The 
number of seconds which elapsed between the flash and 
the sound, was noted by chronometers furnished by Bre- 
guets, one of which denoted even the sixtieth of a second. 
A singtilar fact in the course of the experiments was, that 
the firing was distinctly heard at Ville-Juif, by all the gen- 
tlemen, without difficulty, while at the other station 
not one half the sounds were audible. Very little wind 
prevailed, and what there was, was in favor of the persons 
stationed at Montlhery. The reporters do not undertake 
to explain the cause of this difference; for, say they, we 
can only offer to the reader, conjectures void of proof. 
The result of their trials, after all due allowances, is, that 
at the temperature of 50° I’. the velocity of sound is 173.01 
toises, 337.2 metres, 1106-3026 English feet per second. 
36. Steel._—The Society of Encouragement at Paris, has 
decreed a gold medal to M. Pradier, who has brought his 
stee] instruments to the highest degree of perfection. He 
has discovered the valuable art of rendering steel very 
hard, and at the same elastic. His steel blades can be 
bent double, and are yet so hard as to cut iron, without any 
injury whatever to the edge, however fine and thin it may 
be. This operation was many times repeated by M. Pra- 
dier, in presence of the committee, and always with suc- 
cess. 
37. Sal-Ammoniac.—By the accidental combustion of a 
bed of coal in a mine near St. Etienne io France, in a situ- 
ation where it could not be extinguished, there is exhaled, 
in addition to the usual products of the combustion of coal a 
vapour which becomes condensed on the adjacent substan- 
ces, in the form of a white salt. It was considered by the 
country people as salt-petre, and some of the physicians 
supposed it to be alum. But from experiments made in 
the laboratory of the school of mines it proved to be very 
pure sal-ammoniac, (hydro-chlorate of ammonia.) During 
a few dry days the ground becomes covered with an efflo- 
rescence of this salt, and it continues to increase till dissolv- 
ed by rain. In the interior of an uninhabited house, are 
found those fine specimens which now make a show in some 
cabinets. During the years 1818 and 1819, the production 
