916 Transactions of the American Institute. 



top is a small lamp in which is placed some common resin, and when 

 about to be used a small piece of phosphorus is put into the cup ; 

 this phosphorus will ignite the resin the moment the float comes to 

 the surface. 



Prof. J. A. Whitney remarked that, it is well known that where 

 air is compressed, there is so much heat evolved, and so much power 

 lost. Thu» it would seem that it would work against the operation 

 of the float. 



Mr. Shelburne thought that the burning resin could be seen but a 

 short distance on water, particularly in rough weather. If the 

 weight of a diving bell was suflicient to sink it to the bottom, it 

 would remain there, perhaps just touch the bottom ; but if a portion 

 of the weight of the bell was removed, it would commence to rise 

 with considerable velocity. Therefore, beyond a certain depth, this 

 instrument would not rise. 



Dr. L. Bradley read the following paper : 



AUKOKA BOREALIS. 

 By L. Bradley, M. D., Jersey City, N. .J. 

 In treating the interesting and important subject of aurora bore- 

 alis, I deem it necessary to premise by a general but brief examina- 

 tion of the phenomena, the causes and the effects of atmospheric 

 electricity, in order that we may deduce, if possible, a rational theory 

 of the essential nature of the aurora itself. 



ATMOSPnERic Electeicity 

 Plays an important part in all atmospheric phenomena, either as a 

 cause, a concomitant, or an effect. The formation of fog ; the fall of 

 rain and of snow ; in storms, generally ; in lightning, and in many 

 phenomena which do not possess the character of lightning. Under 

 the name of Castor and Pollox, the ancients designated the bright 

 light which, in stormy weather, sometimes invests the projecting 

 angles and the metallic parts of bodies. 



Sailors tell us of St. Elmos fires, which sometimes appear at the 

 mastheads and yardarms of ships, which, in extreme cases, make a 

 peculiar noise, similar to that of electricity, where it escapes into the 

 air under the influence of powerful tension. Cases are related in 

 which soldiers and cavalry have seen fires shining on the points of 

 their bayonets and swords. The spires of churches and other pub- 

 lic buildings, are sometimes enveloped in a similar manner. Most 



