Intelligence and Miscellaneous Articles. 403 



the stratum-interval has by the rarefaction of the gas been raised 

 to twice or three times its first-measured value, then in all the 

 other tubes the intervals have been doubled or trebled. 



The tube-diameters in my experiments varied between 2 millim. 

 and 4 centim. The above-mentioned regularity came out, indepen- 

 dently of whether the different cylinders formed separate vessels 

 with two metallic electrodes each, or whether, united into a single 

 tube, they were inserted in a line one behind another in the current. 



The law is moreover found to hold good equally whether the 

 mean interval be taken from a large or a small number of strata, 

 provided the numbers in the different tubes be equal, although at 

 the same time the absolute value changes. From this it can be 

 concluded that each single interval also increases in accordance with 

 the above-mentioned law. 



The value of the mean interval is found with great regularity to 

 be, in every tube, as much smaller as the number of strata from 

 which it is derived is greater. Yet the amplitude of the undulation, 

 multiplied by the greatest number of strata employed, never reaches 

 the value of the smallest of the single intervals. Consequently, 

 from the abova law it follows that, if in any tube the magnitude of 

 the mean stratum-interval for a series of gas-densities D v D„ . . . D n 

 is known, and also, for a number of other tubes, each value of the 

 mean interval that corresponds to any one of those densities, the 

 number of the strata which these tubes can show at all the densities 

 from D x to D n can be calculated. 



The proportion — = — - permits us to conclude that the func- 

 Jo J s 

 tion according to which the mean interval varies with the gas- 

 density is the same for tubes of different widths. Experiments 

 for the purpose of ascertaining that function gave the following 

 result : — 



If the rarefactions of the gas increase in a geometrical series, the 

 stratum-intervals are augmented also, very nearly, in a geometrical 

 series. But the exponents of the two series are not identical ; 

 that is, the stratum-intervals are not (as was once maintained by 

 the other side) inversely proportional to the pressure of the gas. 

 On the contrary the measurements prove that the intervals increase 

 much more slowly than the rarefactions — approximately at the rate 

 of -| when the rarefaction is 3. I will defer more definite state- 

 ments until I have determined the exponents with the greatest 

 possible exactness, for which I am at present experimenting on a 

 Toepler pump in the form described by von Hagen*. — Monatsbe- 

 riclite der Kon. ATcad. der Wissenschafteu zu Berlin, 1881, pp. 876- 

 878 (separate impression, communicatd by the Author). 



ON THE ELASTICITY OF EAEEFIED GASES. BY E. H. AMAGAT. 



This subject has already been treated by Mendeleef, Kirpitchoff 

 and Hemilian, by Silgerstrom, and by myself. Those researches 



* Wied. Ann. xii. p. 425. 



