146 ASTRONOMY FOR 1889, 1890 



where A A represents the correctiou to the assumed coustant of aber- 

 ration. The direct inference from these figures is that in 7 months 

 the latitude of Berlin decreased 0".44. Pulkowa showed about the 

 same time a similar change : 



Epoch. Latitude of Pulkowa 



1882.31 +59° 4ti' 18".52 



1883.51 18". 54 



1884.70 18". o3 



1885.23 18". 31 



1885.31 18". 30 



a decrease of 0".3;3 from 1884.70 to 188r).:;i. 



The general agreement of these results certainly calls for furtlier 

 investigation ; and to test the matter Mr. Preston has been sent out by 

 the U. S. Coast Survey, and Dr. Marcuse by the International Geodetic 

 Commission, to Honolulu, which is at the opposite end of the earth's 

 diameter from Berlin, and by simultaneous observations at these two 

 stations it is hoped the question will be settled. 



It is quite possible that the origin of the apparent change at Berlin 

 in 1884-1885 is meteorological, a view to which Dr. Poerster inclined in 

 bringing the matter before the Association Geodesique in 1888. The 

 whole question is, then, whether there are changes in the disposition of 

 atmospheric strata sufficient to account for the facts observed, or the 

 axis of rotation and the axis of inertia of the earth are not sensibly 

 coincident. 



A com])lete resume of the subject is given by M. Tisserand in the 

 Bulletin Astronomiquc for September, 1890. 



Mr.Ilicco has experimented with a somewhat novel demonstration of 

 the rotundity of the earth. At the observatory of Palermo, which is 

 situated at a distance of 1| miles from the Mediterranean and 23G feet 

 above its level, a great number of photographs of the sun reflected from 

 the surface of the water have been taken a few minutes after rising or 

 before setting, and they show that the diameter in the plane of reflec- 

 tion is less in the reflected image than in the direct. This deformation 

 is due to the fact that the surface of the water forms a cylindrical 

 mirror, with axis horizontal and normal to the plane of reflection. The 

 amount of the observed flattening accords well with that demanded b^' 

 theory. 



Standard time. — The introduction of the system of standard time, 

 which has been found of such practical usefulness in the United States, 

 has been quietly agitated in other countries for several years past, and 

 a well-written article u])on the subject by Dr. Eobert Schram will be 

 found in the Obi^ervatory for April, 1890. The adoption of a uniform 

 time system, the time of the fltteenth meridian east of Greenwich, has 

 been very favorably looked upon in Austria and Germany for railroad 

 purposes. 



