PROGRESS IN ASTRONOMY — PUISEUX. 139 



observatory at Meudon. Bosler has succeeded in proving that in 

 each locality there is a definite direction not only for the earth cur- 

 rent but also for the disturbed magnetic field and this takes place as 

 if due to the direct action of a current upon a magnetized needle. 

 Another result of the same research was to show yet more clearly that 

 the years when the sun spots have been the most numerous have 

 been those when Encke's comet has been the most brilliant. 



The total solar eclipse of April 28, 1911, was observed by several 

 expeditions sent for that purpose to Vavau of the Tonga Islands. 

 The weather was unfavorable. We must mention in passing one new 

 result, the photograph taken by Father Cortie of the extreme red end 

 of the bright line spectrum. 



The army of minor planets continues to grow. The most inter- 

 esting without doubt was that observed on October 3 and 4 atVienna 

 and Copenhagen and designated by the letters MT. Its motion deter- 

 mined at that time indicated that its distance was as small as that of 

 Eros. But it could not be found again on subsequent days. We are 

 forced to believe that its brightness varies rapidly and that it was 

 visible on the earUer dates because of an exceptional temporary 

 brightness. 



Bu'kland, while trying to reproduce the solar corona by means of 

 the luminous phenomena about an electrified sphere, got a very close 

 representation of the ring system of Saturn. He was thus led to pro- 

 pose a new theory of those singular objects. Particles of radiant 

 matter, emitted from Saturn, reach a certain distance, make their 

 revolutions according to the third law of Kepler, and serve as absorb- 

 ers and resonators for the luminous energy coming from the sun. 



The flattening of the planet Mars and the orientation in space of its 

 axis of rotation rested until recently upon very discordant data from 

 the micrometer. H. Struve, in a communication to the Berlin Acad- 

 emy of Sciences (Nov. 30, 1911), showed that by a very laborious but 

 surer process depending on the variations in the orbits of its satellites, 

 he had reached much better values. The best series was furnished 

 by the powerful instruments of the Lick and the Yerkes Observa- 

 tories. A very useful series of photographs of the satellites was ob- 

 tained at the observatory at Pulkova by Kostinsky. The figure 190.4 

 for the reciprocal of the flattening and 202.7 for the ratio of the force 

 of gravity to the centrifugal force at the equator will doubtless receive 

 only insignificant changes. 



The topography of the moon will now have a more solid basis as the 

 result of the catalogue of 2,885 objects published by Saunder and 

 based upon measures of plates taken at the Paris and the Yerkes 

 Observatories. It is already in use at the Paris Observatory in a 

 study of the libration of the moon. The uncertainty of a position 

 derived from three plates appears to be less than 0.15". On our own 



