A. MATHEMATICS AND ASTRONOMY. 13 



least thirty seconds of arc, which corresponds at the sun to 

 fifteen thousand miles. He finds also that the whole amount 

 of heat sent from the ring of photosphere around the sun is 

 less than that received from the nucleus of a single solar 

 spot. 6 i?, LXXX., 748. 



SOLAR SPOTS AND TERRESTRIAL PHENOMENA. 



Fritz, so well known by his studies upon the aurora, and 

 especially by his great chronological catalogue of aurorse, 

 states that, after renewed investigation and comparison of 

 thunder-storms in various portions of the earth, he is again 

 forced to the conclusion that there is no perceptible definite 

 connection between the frequency of thunder-storms and 

 auroras, nor between these storms and the solar spoLs, so far 

 as observations from over thirty places can afford any result. 

 Some of the series employed by him reach back to 1755. 

 He has also studied the series of observed heights of rivers, 

 especially the Seine, at Paris, the Rhine, the Elbe, the Do- 

 nau, and other German rivers. This comparison shows that 

 between 1785 and 1844 there was a comparative coincidence 

 in the periodical changes of depth of water and sun-spots, 

 but that the law is reversed from 1844 to 1867, similarly to 

 the reversal found by Professor Wolf, who compared the 

 rainfall itself with tlie sun-spots. Kleiii's Wochenschrift, 

 1875,238. 



ON THE RELATIVE TEMPERATURE OF VARIOUS PORTIONS OF 



THE SUN. 



In a second communication to the French Academy of 

 Sciences, Professor Langley, of Pittsburgh, has given the re- 

 sults of some measurements of the relative temperatures of 

 the solar surface. This subject was first carefully investi- 

 gated by Laplace, who showed that the solar atmosphere 

 absorbed the light that emanates from its nucleus to such an 

 extent that were its atmosphere removed we should receive 

 twelve times more light than at present. The parallelism 

 that exists between the phenomena of light and heat would 

 lead us to expect a result somewhat of the same sort, in case 

 we could measure the heat of the sun. Professor Langley 

 has therefore compared the apparent temperature of ever}'- 

 portion of the solar disk, as Bouguer did for the solar light 



