266 Prof. 11. Clausius on a new Mechanical Theorem 



record of the atmospheric electricity on that day. The Astro- 

 nomer Royal informs me that the atmosphere was + on the 

 morning of that day, but that of the afternoon there is no record. 



§ 51. The following attempts were made to measure approxi- 

 mately the temperature (1) at which a hot insulated iron ball com- 

 menced or ceased to discharge — electricity when at a distance 

 of 2 inches from an electroscope, (2) at which an insulated iron 

 ball begins or ceases to discharge + electricity at the same dis- 

 tance of 2 inches, (3) at which there is no sensible difference 

 between the discharge of + and — . These experiments were 

 checked by examining the temperatures at which an insulated iron 

 ball on cooling (1) commences to be able to receive — , (2) com- 

 mences to be able to receive + , and (3) freely and equally 

 receives both. 



§ 52. Experiments. — The heats of balls at the critical tempera- 

 tures were taken by plunging them into weighed quantities of 

 cold water, weighing them both together. Taking into account 

 the weight and specific heat of glass, and calling the sum of 

 the heat-units in one gramme of iron from 0° C. to the tempe- 

 rature t° C, 



telfy, 

 it was found that 



= 83-7J W 



= 115-91 <2) 



= 116-3/ w 



= 145-11 m 



= 137-0/ (o) 



At (1) both electricities cease to be discharged, and the insu- 

 lated iron can serve as a proof plane for both kinds. Between 

 (1) and (2) — electricity is discharged only, and the insulated 

 iron may serve as a carrier for — electricity, but not for -f . 

 At (3) and above, both electricities are discharged equally, and 

 the iron refuses to receive a charge of either kind. 



August 28, 18/3. 



XXXII. On a new Mechanical Theorem relative to Stationary 



Motions. By K. Clausius. 



[Concluded from p. 244.] 



7. rjlHE above-illustrated notion of the phase, which refers 



-IS- to periodic changes in the motion, can be employed in the 



consideration of motions which take place simultaneously in 



closed paths. But when we have a system of points which, 



though moving in a stationary maimer, do not describe closed 



