590 SCIENTIFIC RECORD FOR 1885. 



Tliomsou had never seen any reason at all for believing in Boltzuiaun's 

 theorem. J. J. Thomson said that he thought the reason that the value 

 of the specific heats of a gas, as found by experiment, did not agree 

 with the value given by Boltzmann's theorem was because Boltzmann's 

 theorem was not true. Hicks stated that to him one of the greatest 

 objections to this theorem was the difficulty in believing that the mean 

 energy of any vibration whatever of an atom was susceptible of unlim- 

 ited increase. Osborne Reynolds remarked that the kinetic theory is 

 supposed to be true only in so far as the assumptions on which it is 

 based represent the actual conditions. In any gas the mean energies of 

 translation in which there is most rapid communication and no appre- 

 ciable resistance will be much greater than the mean energies of vibra- 

 tion to which there is all the resistance consequent on the radiation and 

 in all probability bat little communication, (TV^a^wre, August, October, 

 1885, XXXII, 352, 533.) 



De Roinilly has modified the form of vacuum jet which he suggested 

 in 1881, and to which he gave the name of pneole. In its original form a 

 jet of water or of mercury was thrown upward from a circular orifice into 

 a second and similar one placed above it, carrying the surrounding air 

 with it. Since the interior parts of the solid column contributed nothing 

 to the effect, the periphery alone being useful, the author has placed 

 a solid cylinder within the jet so as to make the opening annular. The 

 liquid is thrown up by centrifugal action. A mercury apparatus of this 

 ilescription, turned by hand, made a barometric vacuum in a globe of 

 (3QQC. c. capacity in about six minutes. (</. Fhys., August, 1885, II, iv, 

 3G6.) 



Wilde has made a series of experiments on the velocity with which 

 air rushes into a vacuum. Theory assumes that air rushes into a vac- 

 uum with the velocity which a heavy body would acquire by falling 

 from the top of a homogeneous atmosphere, i. e., a velocity of 1,332 

 feet a second. The apparatus consisted of two strong cast-iron cylin- 

 ders, the snmller having a capacity of 573 cubic inches and the larger 

 of 8,459 cubic inches. To the smaller a compression pump and pressure 

 gauge were attached, to the larger an exhausting pump and a vacuum 

 gauge. The air was discharged from the smaller cylinder into the 

 large one through a disk of tinned iron 0-75 inch in diameter, and 0-01 

 inch thick, pierced in the center with a circular hole 0-02 inch in diam- 

 eter. The vacuum M\as G inch mercury, and the pressure varied from 

 10 to 135 pounds i)er square inch. The maximum velocity observed 

 was 1,225 feet per second, and this only at the commencement, the 

 values in general being considerably less than theory indicates, though 

 at forty atmospheres the theoretical velocity would be reached. Experi- 

 ments made on the discharge of the compressed air into the atmosphere 

 showed that the times of each discharge from 120 pounds to 15 pounds 

 effective j)ressure are identical with the times of discharge from 135 

 pounds to 30 pounds absolute pressure into a vacuum. Hence the au- 



