A. MATHEMATICS AND ASTRONOMY. 41 



York), in which he gives the results of his investigations into 

 the difference of intensity of heat transmitted from different 

 parts of the sun's surface. His instrument has a focal length 

 of fifty-eight feet, being a telescopic tube of that length, 

 within which diaphragms may be placed so as to expose to 

 view only definite small portions of the solar disk. By 

 means of three actinometers which record simultaneously 

 the rays of heat received first, from the entire area of the 

 solar disk, second from a central region, third from a zone 

 at the border he is able to arrive at the desired comparison. 

 In order to insure greater exactness, he surrounds his three 

 actinometers with wooden jackets through which a steady 

 stream of water is circulated, thereby keeping the chambers 

 at a uniform temperature. He concludes that the radiation 

 at the edge of the solar disk is but two thirds of that at the 

 centre, while the total absorption of the solar atmosphere is 

 about one seventh of the radiation emanating from the pho- 

 tosphere. Ericsson'' s Solar Investigations^ Neio Yorh^ 1876. 



DISTRIBUTION OF STANDARD TIME IN SWITZERLAND. 



The report of Professor Hirsch, Director of the Observatory 

 of the canton of Neuchatel,in Switzerland, gives an account 

 of the methods adopted at Neuchatel for distributing accu- 

 rate time throughout the neighboring country. He says the 

 importance of telegrajDhic transmission of astronomical time 

 for the development of accurate horology is fully apj^recia- 

 ted both in Neuchatel and the neighboring cantons. Grad- 

 ually the system of transmission of time has been extended 

 so as to embrace even the canton ofYaud; and, among other 

 cities, those of Neuchatel, Geneva, St. Croix, Locle, and numer- 

 ous other stations. In accordance with a formal agreement 

 between the canton of Vaud and the canton of Neuchatel, 

 the government of the former pays an annual sum toward 

 the support of the Neuchatel Observatory ; the organization 

 of the whole service being left with the observatory, but the 

 local expenses of receiving time signals are charged to the 

 government of the canton of Vaud. It w^ould seem, howev- 

 er, tliat the organization of the astronomical and telegraphic 

 work has not yet reached the perfection which it has attained 

 in England, since it is reported since last year that the signal 

 at one station has ceased altogether, while at another it was 



