August 2, 1900] 



NA TURE 



325 



been thought worth while to bring the co-ordinates past the 

 epoch 1880. 



Commencing astronomical observations in l86i with a very 

 small instrument, Prof. Burnham obt lined a six-inch equatorial 

 from Alvan Clark in 1869, with which he commenced system- 

 atic work on double stars in 1872. Since that time his observa- 

 tions have been made with instruments of varying aperture, 

 9'4, 12, I5"5, 16, 185, 26, 36 and 40 inches respectively. 



Especially interesting is the fact th it a great proportion of the 

 pairs discovered have been found to be physically binary, and 

 that these are generally closer and more difficult to measure 

 compared with those in slower motion. 



A special list of quadruple stars is given, and various measures 

 ive been obtained by the cooperation of other observers with 

 different instrumental equipment. The stars are arranged in order 

 " right ascension ; and besides the present elements, a short de- 

 Bription of special particulars with comparative previous mea- 

 ires are added to each where necessary, and several illustra- 

 )ns are given of the instruments used in the course of the work. 



large battery and the large condenser, to photograph com- 

 paratively slow oscillations. I have lately succeeded in obtaining 

 photographs of oscillations eight hundred a second ; and experi- 

 ments on the permeability of iron wire with powerful discharges 

 with such low periods are now in progress. 



That most discharges of lightning are to-and-fro, or oscillatory, 

 I feel sure, and I have outlined my method of proof ; but this 

 was hardly necessary, for the photographs of the long sparks 

 shovy on mere inspection the toand-fro motion, for on the line 

 of discharge forks can be observed pointing in opposite direc- 



SOME RESULTS OBTAINED WITH A 



TORA GE BA TTER V OF TWENTY THO US AND 



CELLS} 



'HE remarkable development of practical employments of 

 electricity have put the professor of physics at a dis- 

 Ivantage, compared with the electrical engineer. The latter has 

 at his service thousands of electrical horse-power, while the 

 college instructor can barely obtain fifty. The engineer can 

 experiment with enormously strong currents and study their 

 effects in chemical industries, and in the production of intense 

 heat. Thus the study of the manifestations of electricity on a 

 great scale seems to be relegated to the electrical engineer. 



There is one direction, however, in which the university pro- 

 fessor can enter into competition with the engineer and even 

 surpass him in resources. This direction is in the field of high 

 electromotive force ; and I wish to call your attention to some 

 results which I have obtained with a storage battery of twenty 

 thousand cells. For several years I have had at my command 

 ten thousand cells ; and the plant has proved so practical that I 

 resolved last autumn to double the number of cells. The battery 

 is now finished, and you will have an opportunity of seeing its 

 manifestations. 



With twenty thousand cells of the Plante type I can obtain 

 forty two thousand volts, and by the use of Leyden jars I can 

 step up to three million. I cannot go higher, for the very 

 interesting reason that air at atmospheric pressure becomes a 

 fairly good conductor beyond two million volts, and it is im- 

 possible to charge Leyden jars to this potential, or to produce 

 sparks in a laboratory of greater length than seven feet. To 

 obtain the greatest manifesta-ions of three million volts, it would 

 be necessary to put the apparatus in an open field at least 

 thirty feet from the ground, and remote from all other objects. 

 Jars and circuits charged to this high voltage emit a luminous 

 discharge to the floor of the room and to the brick walls, and 

 indicate by this inductive discharge the presence of steam pipes 

 twenty feet distant. The air breaks down quickly under this 

 powerful electric stress, and, indeed, acts like a rarified gas. 



Nevertheless discharges of electricity six and seven feet long 

 are of interest, especially to many of you who are citizens of 

 Boston, where Benjamin Franklin was born. These discharges 

 closely resemble lightning, and one can reproduce all the photo- 

 graphic effects obtained by students of this astounding natural 

 phenomenon. I have discovered the interesting fact that these 

 long sparks are oscillatory. 



The method of proof is this : I connected the condensers 

 which were used in series to produce the high potential of three 

 million volts, in multiple with a known self-induction. The 

 discharge was then photographed. Here is one of the results : 

 The distance between these bead-like figures from centre to 

 centre represents one five-thousandth of a second (Fig l). 

 When the condensers are connected in series through the same 

 self-induction the discharge still remains oscillatory, but of a 

 much higher period ; we are sure of this fact from Lord 

 Kelvin's discussion of the limits of oscillatory action. You will 

 perceive from Fig. i that I have been able, by means of the 



1 Paper read by Prof. John Trowbridge at a meeting of the American 

 Academy of Arts and Sciences, held in the Jefferson Physical Laboratory, 

 Harvard University, Cambridge, U.S. 



tions, showing that the discharge changed from positive to 

 negative. These forks, or branching discharges, have an inter- 

 esting peculiarity, which was brought out in the following 

 manner. A sheet of plate glass about five feet square was 

 placed between the terminals of the high potential apparatus, 

 and a minute hole was bored in the middle of this plate. 



This hole could be made very small by plugging the orifice 

 with paraffin, and making needle-holes in the paraffin. When the 

 spark terminals were opposite the hole, each a foot and a-half 



from it, the spark sought the hole. A photograph of the spark 

 (Fig. 2) shows an apparent breadth of spark much greater than 

 the diameter of the hole ; indeed, the minute size of the latter 

 cannot be reproduced on the negative ; while the spark seems to 

 the eye to be an eighth of an inch in thickness, and actually 

 measure? about a millimetre in diameter on the negative. The 

 reason of this phenomenon, I believe, is that only a portion of 

 the discharge passes through the hole. This can be shown in 

 the following manner. The terminals were not placed oppo- 



FlG. 3 



site the hole, but to one side of it, about a foot from it, and 

 about half a foot from the glass. The discharge then jumped to 

 the glass (Fig. 3), and pursued a devious way to the hole. 

 When the hole was completely filled with paraffin the spark 

 still jumped to the glass, apparently piercing a hole through it ; 

 but this was impossible, for the thickness prevented this. The 

 discharge was continued evidently by an inductive action. I 

 next restored the orifice, and, keeping the spark terminals in the 

 last position referred to, I hung a large sheet of paraffined paper 



NO. 1605, VOL. 62] 



