150 PHENOMENA DEPENDENT ON MOLECULAR PATHS 61 



Jochmann, 1 and others related to a series of very different 

 phenomena, which were apparently irreconcilable with the 

 theory, but are all referable to one and the same point of 

 the theory that is easily liable to misconception. 



Starting from the hypothesis that the particles of a 

 gas are in a state of forward motion in straight lines, we 

 have found ourselves forced to the conclusion that, for 

 the elasticity and pressure of a gas to be explained, these 

 motions are executed with enormous speed. A particle of 

 air traverses a path of more than 400 metres in a second, 

 and a molecule of hydrogen a path even four times greater. 

 If these paths are really traversed in a single straight line, 

 as the hypothesis of the theory seems to require, many 

 phenomena are at once unintelligible. 



Smoke can hang in still air for a long time almost im- 

 movable like a cloud. But it would be dispersed in a 

 moment if the air molecules tore the particles of smoke away 

 from each other, and carried them off in all directions nearly 

 500 metres in a second. 



Sulphuretted hydrogen, generated in the corner of a 

 room, must at once be scented everywhere in the whole 

 room if its molecules hastened through the room in straight 

 lines with the speed of 409 metres per second as calculated 

 in 28. On the contrary, we observe that the diffusion of 

 this and other gases proceeds with the utmost slowness. 



Still more convincingly than by this objection the theory 

 seems to be refuted by the fact that gases conduct heat very 

 slowly. For if heat consists in that rapid motion, and if 

 this proceeds in straight lines, it must be propagated so fast 

 by its own agency that a rise of temperature occurring at 

 one point of a gas would be discoverable 400 metres away 

 in no longer than a second ; it must travel, in fact, quite as 

 fast as sound. 



For the same reason it would not be conceivable that 

 the equilibrium of temperature that exists in the earth's 

 atmosphere, where the higher layers are much colder than 

 the lower, could be maintained ; indeed there would be all 

 the appearance of the earth's being surrounded by such good 



1 Pogg. Ann. 1859, cviii. p. 153. 



