220 



ASTRONOMY. 



to a terrestrial arc of one minute — the degree containing sixty of these 

 miles— when in reality it contains G9.5, the error being about one-sixth. 

 This error delayed for many years the discovery of universal attraction. 

 The first time the idea that the attraction of the earth retaining the 

 moon in its orbit is the same thing as gravity, presented itself to New- 

 ton, he failed in the verification, because he then employed the mile in 

 calculating the earth's radius. He thought he must renounce the idea, 

 and he only returned to it when he became acquainted much later with 

 the measurement of a degree executed by Picard, of France. 



The Moon. — M. Janssen has succeeded in j)hotographing the lumiere 

 c-endree or "earthshine" on the moon when three days old. In the 

 photograph the "continents" were to be distinguished clearly from the 

 *'seas." 



Asteroids. — From the Berliner Jahrhuch for 1883 the following is 

 extracted : 



Column I contains the numbers of the minor planets in the order of 

 discovery. Column II contains the mean magnitudes of the corre- 

 sponding planets, and column III contains the means of the magni- 

 tudes of these planets at the times of their discovery. This table is a 

 summary of a more extended one where these quantities are given for 

 each asteroid separately. 



From this table it follows that the discoveries have, on the average, 

 taken place in those parts of the orbits nearer the perihelion than the 

 aphelion, and moreover that the later discovered planets are not spe- 

 viallv fiiinter than those since No. 100. 



List of asteroids discovered in 1881. 



This is possibly 108 Hecuba. 



Jupiter. — The annual report of the Chicago Astronomical Society, for 

 1880-'81, makes an interesting and valuable exhibit of Professor Hough's 

 work for the year iiast. He has reached the conclusion which it would 



