254 M. 0. Szily on the Dynamical Signification of the 



heavy shower of hailstones, will, irrespective of resistance 

 from the air, return to the ground with a certain loss of 

 motion, because the force of impact of the hailstones will be 

 greater on the stone Avhen ascending: than when descending. 

 Now if we substitute gravific corpuscles for hailstones we 

 shall have the same result, though, of course, to a far less 

 extent, owing to the enormous velocity of the gravific cor- 

 puscles compared with that of the hailstones. But unless 

 these corpuscles move with infinite velocity, the force of im- 

 pact cannot be absolutely as great on the descending as on 

 the ascending stone ; and if so it cannot return to the earth 

 with absolutely the same velocity as it left. There must be a 

 loss of motion, however small that loss may be. 



In all probability this is a point too nice ever to be deter- 

 mined by experiment. This loss of motion might, however, 

 if real, be detected in the case of comets or planets with very 

 eccentric orbits. The tendency of this canse would be to 

 produce a shortening of the major axis of the orbit of the 

 planet or comet, and of course a corresponding decrease in 

 the period of revolution. 



If gravitation were an impact, no planet nor comet could 

 move everlastingly in an elliptic orbit. But the mutual disturb- 

 ing forces of the planets will always maintain them in elliptic 

 orbits ; and it would therefore seem to follow that gravity 

 alone, without any resisting medium, would ultimately bring 

 the planets to the sun. 



The same results will follow on the supposition that gravity 

 is caused by unequal pressure in a substance continuously 

 filling space. 



XXXIII. On the Dynamical Signification of the Quantities 

 occurring in the Mechanical Theory of Heat. By 0. Szily, 

 of Buda-Pesth*. 



ONE of the most important physical fundamental notions 

 is that of temperature ; all the quantities of the theory 

 of heat, nay, every physical quantity stands in relation to 

 this ; and yet there is perhaps not a single notion in the entire 

 range of physics which has been so indefinite and obscure. 

 Both the rational definition and the measurement of tempera- 

 ture have for their sole basis the frequently discussed but not 



* Translated from a German version, communicated by the Author, of 

 a memoir which appeared in the Hungarian Miiegyetemi Lapok, vol. i. 

 p. 165. On perusing- the proof sheet of the English translation, the 

 author has made a few modifications, and inserted the results of some of 

 his new investigations on the subject. 



