134 EECOKD OF SCIENCE FOR 1886. 



Mr. Hill has received the gold medal of the Royal Astronomical 

 Society for his laborious and masterly researches upon this difficult 

 subject. 



An interesting historical note on the inequalities of the motion of the 

 moon which depends on the figure of the earth, is given by Professor 

 Hall in the Annals of Mathematics, vol. 2, No. 5. 



Mars: The '■' canals ^^ of Mars. — M. Perrotin and his colleagues at 

 Nice succeeded in recovering many of Schiaparelli's enigmatical " canals" 

 at the last opposition of Mars, although the planet was seen under very 

 unfavorable conditions. Its apparent diameter at this opposition was 

 only 14", against 25" at the opposition of 1877, when the canals were 

 discovered. The canals were made out by several observers at Nice, 

 and were recognized as having the same general outline and position 

 attributed to them by Schiaparelli in 1882. They seem, therefore, to be 

 essentially permanent, forming a sort of network of grayish lines pro- 

 jected against the brighter equatorial regions of the planet. Compared 

 with the thickness of the spider lines of the micrometer, the finest of 

 these lines appear to have a width which corresponds to an arc of 2° 

 or 3° on the surface of Mars. Some of them measure from 50^ to 60° 

 in length, and several are double, composed of lines strictly ijarallel, 

 separated, according to Schiaparelli's estimate, by intervals of from 6° 

 to 12°. All of this speaks well for the purity of the atmosphere at 

 Nice, the excellence of the 15-inch Henry refractor, and the keenness 

 of the observers. 



During the study of the planet (from the end of March to the middle 

 of June) some change seemed to be taking place near Kaiser Sea. On 

 May 21 this region, from 10<^ to 55° north latitude, was hidden by a 

 luminous veil somewhat softer in color than the continents, very much 

 as if clouds in regular parallel bands were stretched across the planet 

 from northeast to southwest. At moments these clouds became trans- 

 parent, exposing the outline of the prolongation of Kaiser Sea. Other 

 similar cloud phenomena were observed on subsequent days. M. Per- 

 rotin suggests that these phenomena were really produced by clouds 

 or mists circulating in the atmosphere of Mars, and concludes that they 

 are, in such case, the act of an element belonging to the atmosphere, 

 or to the surface of the planet, susceptible of motion and modification 

 in a comparatively short time. 



Mr. Denning, who has been an attentive observer of Mars, has not 

 been able to make out the canals in the detail assigned to them by 

 Schiaparelli, although he has distinguished a large number of appear- 

 ances highly suggestive of these configurations. Mr. Denning con- 

 cludes a review of his recent observations of the jilanet (Nature, 34 : 

 105) as follows : 



"Many of our leading treatises on astronomy attribute a dense atmos- 

 phere to Mars, but nothing has been observed during my recent obser- 

 vations to corroborate this theory. It seems to me far more plausible 



