Natural Philosophy. — Mechanics. 195 
instruments at once, with the greatest facility and correctness. 
He plays on the violin in the usual manner, and on the violin- 
cello by means of his feet. His right foot goes into a sort of 
shoe at the end of the bow, and in consequence of his right 
thigh being supported by a spring attached to the chair on which 
he sits, he has the full command of his foot, without suffering 
any fatigue. By means of his left foot he acts upon a set of le- 
vers, by which he shortens the strings with great facility. Mr 
Watson has frequently played thirteen and fourteen hours in one 
day, without any extraordinary fatigue. 
MECHANICS. 
9. Physical Strength of Men. — M. Coulomb, in his fine 
Memoir on the Physical Strength of Men, after remarking that 
he had always found the grenadiers to perform a third more 
work than the other companies, observes, that the mean quanti- 
ty of action varies with the nature of the food, and particularly 
with the climate. I have executed,'” he says, great works 
at Martinique by the troops, when the thermometer rarely stood 
‘‘below 68° Fahrenheit; and I have executed in France the same 
kind of work by troops ; and I am assured, that under the lljth 
degree of latitude, where the men are almost always inundated 
with perspiration, they are not capable of half the quantity of 
daily worh which they can furnish in our climate.''’' The follow- 
ing experiments by Peron, with Pegnier-s dynamometer, shew 
that the individual strength depends also on the climate. 
English, 
- 
71.4 
French, 
- 
69.2 
Timor, 
- 
58,7 
Van Diemen’s Land, 
- 
51,8 
New Holland, 
- 
5QJ ^ 
HYDllODYNAMldS. 
10. Oh the AppVication of a Jet of Water te drive a Water- 
wheel. — M. Morosi of Milan has found that the force of a jet of 
water is greatly increased by raising a rim about half an inch 
high round the circumference of the disc upon which it is 
thrown. The following results were obtained by directing a 
stream of water one inch square, against a plain disc, and one vVith 
a raised edge. 
