December 31, 1915] 



SCIENCE 



943 



space in front of the cathode (shown by the 

 dotted line mn in the figure). 



The usefulness of the above described tube 

 for many laboratories is limited because liquid 

 air is used in its initial adjustment and sub- 

 sequent operation. If desired the bulb B may 

 also be sealed off. The only disadvantage is 

 that this fixes the gas content in the tube. In 

 case no liquid air is available it is still possi- 

 ble to construct the tube provided access may 

 be had to a good pump. In this event the dis- 

 charge tube should be washed out several times 

 with the desired gas, in order to remove every 

 trace of air, and then sealed off when the 

 beams are brightest. This gives a permanent 

 tube provided the occluded gases in the elec- 

 trodes and walls of the vessel do not in time 

 let the vacutun down. Danger from this 

 source, however, may be largely avoided by 

 gently heating the tube during exhaustion. 

 The obvious advantage of a charcoal bulb is 

 that the proper exhaustion can always be 

 reached and at the same time the discharge at 

 various stages of exhaustion successively ex- 

 hibited. 



It should be added that the best results only 

 are obtained when the hollow cathode C, which 

 is an altmainum cylinder closed at the ends 

 with aluminum discs through the center of 

 each is cut a rectangular opening about 1 mm. 

 by 6 mm., is placed exactly on the axis of the 

 tube connecting the bulbs M and N. The cor- 

 rect position is shown in the figure, end view 

 at 6, and side view at d. The discharge leav- 

 ing the cathode, confined in a narrow tube as 

 here, is always along the axis of the glass 

 tube, regardless of the alignment of the cath- 

 ode. In other words, the shape of the glass 

 tube rather than the shape of the cathode 

 determines the position of the cathode beam. 

 Lack of alignment is shown at c and e where 

 the opening through the hollow cathode is 

 below the axis and as a result few positive rays 

 get through and show in the bulb M, though 

 they show distinctly at their origin in front of 

 the cathode. To avoid possible lack of align- 

 ment it is advised to make the hoUow cathode 

 C of such diameter so as to fit snugly into the 

 neck connecting M and N as shown in a of the 

 figure. 



An interesting test to show that the beam in 

 N is composed of electrons, and that in M of 

 positively charged ions, is to deflect them in 

 turn by a strong electro-magnet. The cathode 

 beam is readily deflected while the positive 

 ray beam is but little deflected and that in the 

 opposite sense. This is in full agreement vnth 

 the theory of the magnetic deflection of mov- 

 ing positive and negative charges. 



Chas. T. Knipp 



Laboratory of Physics, 

 University or Illinois, 

 October 9, 1915 



THE AMERICAN CHEMICAL SOCIETY 

 The fifty-first meeting of the American Chemical 

 Society was held in Seattle, Washington, August 

 30 to September 3, 1915, inclusive. The members 

 came to Seattle from many directions, although a 

 special car brought thirty-three over the Great 

 Northern railroad on the evening of the thirtieth. 

 Those who came in the special car spent August 

 29 in Glacier National Park. The meeting was 

 opened by an address of welcome by the dean of 

 the University of Washington, to which response 

 was made by President Herty. A general meeting 

 was then called to order and listened to an address 

 by Leo H. Baekeland on "Chemical Industry" and 

 a second address by H. K. Benson on "Industrial 

 Eesources and Opportunities of the Pacific North- 

 west. ' ' Following these addresses the society con- 

 tinued in general session until noon of the follow- 

 ing day, holding public symposiums. 



On Wednesday afternoon the various additional 

 programs were held as well as the election of addi- 

 tional ofiicers for 1916. On the evening of the 

 thirty-first a complimentary smoker was given by 

 the Seattle Commercial Club, at which Professor 

 Meany gave a beautifully illustrated lecture with, 

 colored slides on Mt. Rainier. The members were 

 also entertained by a Japanese sword contest and 

 by a Chinese cartoonist. Besides the usual attrac- 

 tions of the excursions and the President 's address, 

 the ladies were given special entertainment of a 

 reception and tea on the university campus Tues- 

 day, August 31, and an organ recital the same 

 evening. On Wednesday they were given a special 

 drive by automobile through the parks and boule- 

 vards of Seattle. On Wednesday the members were 

 treated to an automobile trip through the beauti- 

 ful parks and boulevards of Seattle and on Wed- 

 nesday evening at 8 o'clock, President Charles H. 

 Herty gave his presidential address, entitled "Co- 



