Apeil 6, 1900.] 



SCIENCE. 



553 



lightning is to the electrician what the sea ser- 

 pent is to the zoologist. It has often been seen, 

 but never by those who are most competent to 

 study and describe it, and all efforts to produce 

 ball lightning eifects by artificial means have 

 hitherto failed. But these twelve negatives 

 show with perfect distinctness discharges of 

 this character. They could be seen while they 

 were being photographed. They looked like 

 little spheres of light, which traveled over a 

 non-conducting plate, forming the insulation of 

 a condenser. They traveled very slowly among 

 the sparks of the ordinary disruptive discharge. 

 Their speed was usually at the rate of an inch 

 in three or four minutes. Their tracks showed 

 with the greatest sharpness among the more 

 indistinct flashes of miniature lightning. They 

 sometimes jump for a quarter to a third of an 

 inch, with such quickness that the eye can 

 hardly follow them. Five or six such spheres 

 of light sometimes appear at once, each follow- 

 ing its own track. Sometimes one will cross a 

 track previously traced by another, but it never 

 follows the track of another. 



By proper illumination of the room the effects 

 of the spark discharges can be nearly obliter- 

 ated in the negative, but the paths of the ball 

 discharges are not materially affected. One 

 negative thus treated had been exposed for 

 thirty- five minutes, and the ball lightning tracks 

 were most elaborate. The branching network 

 of lines must have been produced by hundreds 

 of these little spheres. 



The same results can be obtained by fixing 

 the negatives without any developing process. 

 Everything then vanishes from the plate but 

 the ball discharges. 



Professor Nipher stated that this phenomenon 

 could not be identified as the same thing as ball 

 lightning, since the latter had not been studied. 

 But it responds to the same description in many 

 ways. As soon as the ball lightning effects 

 appear, the behavior of the machine changes 

 in a very remarkable way. 



Mr. Koch exhibited an electrical fire an- 

 nunciator. 



Five persons were elected to active member- 

 ship in the Academy. 



William Teelease, 

 Becording Seeretary. 



THE philosophical SOCIETY OF WASHINGTON. 



At the 515th meeting of the Philosophical 

 Society of Washington, held at the Cosmos 

 Club, March 17th, Mr. Abbe called the atten- 

 tion of the members to three interesting works 

 in meteorology : 



1. The work in theoretical physics, viz, the 

 memoir of Professor Marcel Brillouin, explain- 

 ing the formation of cloud and rain in accord- 

 ance with the principles developed by Helm- 

 holtz and von Bezold. The full memoir is 

 published by the Central Meteorological Bureau 

 of France. 



2. A work in experimental laboratory phys- 

 ics conducted by Mr. C. T. R. Wilson, showing 

 how the condensation of aqueous vapor takes 

 place bj' preference upon the negative ions and 

 that such negative nuclei can be formed in the 

 atmosphere by the action of various forms of 

 radiation including the Kontgen Bays, the 

 Uranium rays, sunlight, etc. That, finally, 

 according to Professor J. J. Thomson, we must 

 no longer regard the earth as primarily electri- 

 fied negatively, and acting by induction upon 

 the atmosphere to make it positive. We must 

 regard the atmosphere as a mixture of neutral 

 atoms and positive and negative ions ; the latter 

 being brought down to the earth's surface by 

 rain make the earth negative while leaving the 

 atmosphere positive. 



3. A work of observation in the free air, viz : 

 the Keport of Professor H. Hergesell of Stras- 

 burg, published in the last number of the Zeit- 

 schrift of the German and Austrian Societies. 

 In this report Hergesell presents isotherms, 

 isobars and movements for sea level and at 5000 

 meters and, also, 10,000 meters elevation for 

 three different dates, as deduced from 32 bal- 

 loon ascensions, thus demonstrating the exis- 

 tence of the descending cyclones with cold cen- 

 ters first described by Ferrel. The three 

 memoirs above mentioned were submitted for 

 the personal examination of the members pres- 

 ent. 



Mr. L. P. Shidy read a paper on the State of 

 Progress of our knowledge of the Tides, in 

 which after briefly reviewing the steps by which 

 our knowledge has beeu increased, he presented 

 some of the views of Dr. R. A. Harris in re- 

 gard to the tidal movements in the great oceanic 



