404 Intelligence and Miscellaneous Articles. 



the molecules their normal ratios, and thus reimpart to a muscle the 

 power of contraction. A coagulation, on the other hand, could never 

 disappear instantaneously. 



(7) Making a series of experiments on the same muscle, by- 

 heating it several times successively to the point of zero work and 

 then cooling, I have observed that the greatest ordinate, that in 

 which the mechanical force ceases to increase or to diminish, ap- 

 peared in the next experiment at a lower temperature. I have found 

 that this phenomenon is caused by the remarkable fact that the 

 muscle is more rapidly exhausted at a higher than at a lower 

 temperature. This I proved by putting to work two muscles of 

 the same weight (as nearly as possible) under the same tension and 

 the same irritation, but at different temperatures. At the commence- 

 ment the ordinates at the higher temperature were then always greater 

 than at the lower one ; that is, the muscle raised the weight to a 

 greater height : but the abscissa was always shorter at the higher 

 temperature ; this amounts to saying that then the muscle always 

 ceased working sooner. In consequence of this fact, 



(8) The total work of the muscle is always greater at a low than 

 at a high temperature, all other conditions being equal. 



(9) The increase in mechanical work during increase of tempera- 

 ture is due to the circumstance that the elasticity of the muscle at 

 work increases with increase of temperature. — Comptes Bendus* 

 August 26, 1867. 



ON THE INTENSITY OF THE SOLAR RADIATION. 

 BY M. J. L. SORET. 



The actinometer I use in these researches consists essentially of a 

 thermometer, the blackened bulb of which is placed within an enve- 

 lope also blackened. An aperture, 2 centims. in diameter, in this 

 envelope gives entrance to a solar ray which falls on the bulb of the 

 thermometer. The temperature rises until it loses, either by radia- 

 tion or by contact with the surrounding air, as much heat as it re- 

 ceives from the sun. 



In order to have the instrument always under the same conditions 

 as regards radiation, the envelope is surrounded by melting ice, so 

 that the thermometer is uninfluenced by the reverberation of adja- 

 cent bodies, or the radiation from various parts of the sky. 



Contact with the surrounding air, although the thermometer is 

 protected from the wind, contributes a notable proportion of the 

 cooling, which varies and increases with the atmospheric pressure. 

 If the same observations were always made in the same place, 

 these variations might be neglected ; but this is by no means so if 

 we work at different heights. By direct experiments on the appa- 

 ratus itself I have determined the influence which the barometric 

 pressure exercises on the temperature of the thermometer. The in- 



