Chemistry and Physics. 63 



to the electric discharge in high vacua follows an inverse rule from 

 that governing discharges at ordinary pressures. In air at 

 atmospheric pressure the resistance increases for moderate dis- 

 tances as the length between the terminals increases, while in 

 high vacua the resistance is said to diminish as the distance 

 between the terminals increases. 



If the latter were true it would be so discordant with known 

 laws that I have during several years made experiments with 

 freshly prepared X-light tubes to see what could be learned. I 

 have concluded that the accepted opinion is not correct. When 

 the resistance in high vacua appears to follow another rule from 

 that governing in air it is because the true condition is masked. 

 To show that the same law applies in both cases I mention results 

 obtained from tubes recently prepared for experiments on burn- 

 ing the skin. These had the movable terminals described and 

 figured in my Notes in The Electrical Review for December, 

 1897, and January, 1898. They were carefully prepared with 

 heat and heavy surges during pumping to get the terminals in 

 proper condition for the current afterward to be used in exciting 

 them. In No. 1, the target (anode) was placed forty millimeters 

 from the cathode. In this position the resistance to an amount 

 of current suitable for the tube was equal to four millimeters of 

 air at atmospheric pressure. When the distance between the 

 cathode and target was increased to one hundred millimeters, the 

 resistance increased to ten millimeters of air. 



In No. 2, under the same conditions, the resistance was equal 

 to eight millimeters and twenty millimeters of air. In studying 

 the resistance of high vacua, X-light tubes are valuable as they 

 are very sensitive, and it is important to consider the conditions 

 which determine the production of a regular cathode stream 

 (such as the form of the terminals, the condition of the gas amal- 

 gamated with them) — the establishment of a normal circulation 

 of the residual gases (depending on the form of the tube and the 

 relations of the terminals to it) — the amount of the current and 

 the size of the surges which are sent through the tube. 



11. Studies from the Chemical Laboratory of the Sheffield 

 Scientific School ; edited by Horace L. Wells. — In two volumes : 

 Vol. I, Papers on General Inorganic Chemistry, pp. 444 ; Vol. II, 

 Papers on Organic Chemistry, pp. 379. Yale Bicentennial Publi- 

 cations. New York, 1901 (Charles Scribner's Sons). The 

 Chemical Laboratory, which, as "the Philosophical Department 

 of Yale College," had its beginning in 1847, has the distinction of 

 having been the nucleus which has developed and expanded into 

 the vigorous department of Yale University now known as the 

 Sheffield Scientific School. From those early days until the 

 present time the Sheffield Chemical Laboratory has been active 

 in research no less than in instruction. This fact is well brought 

 out by the Bibliography given on pages 4 to 10 of volume I before 

 us, which, however, is limited to the titles of papers (130 in num- 

 ber) published, or about to be published, by the officers at pres- 



