ASTEONOMY. 307 



it is probable that the latter are closely connected with, elevations of 

 the continents which they skirt, while the oceanic volcanoes are not 

 concerned with true elevatory action. *rhe great volcanic chain of the 

 Pacific approximately divides the earth into two parts, one of which 

 contains the chief proportion of land, while the other contains Australia 

 and nearly all the ocean. And perhaps the area of Australia has been 

 elevated within the ocean hemisphere on account of the deflection of 

 the great Pacific line of action by the northwest line, which passes 

 through Sumatra and the Malay Archipelago, and which meets it at 

 the southeast corner of Asia. 



" Although many of the subjects discussed by Mr. Fisher must remain 

 open questions until we are far better acquainted with the conditions 

 of volcanic action, we think that he has cleverly argued his points, and,, 

 by the frequent application of a rigid mathematical treatment, has re- 

 moved his opinions from the domain of those pure speculations which are 

 too often applied to the explanation of obscure phenomena connected 

 with the physics of the earth." 



Geodesy of Europe. — Two very interesting charts have just been dis- 

 tributed as supplements to the proceedings of the sixth general con- 

 ference of the European Geodetic Survey (held at Munich, in 1880). 

 One of these gives all the telegraphic determinations of differences of 

 longitude, and the other gives all the determinations of latitude and 

 azimuth (separately). Such charts for the United States would be 

 most valuable. 



Atmospheric refraction. — An important memoir on refraction has been 

 lately published by M. Eadan, who, after a discussion and comparison 

 of previous theories, gives formulae and tables for refraction, in whiidi 

 allowance may be made for difference in the rate of decrease of tempera- 

 ture with the height above the earth's surface at different seasons of the 

 year. M. Radan also discusses the case in which the surfaces of equal 

 temperature in the atmosphere are inclined to the earth's surface. 



The Moon. — Selenography has lately received a valuable contribu- 

 tion by the publication of the sketches of portions of the moon's disk 

 which were made by Tobias Mayer, at Gottingen, in the middle of the 

 last century. Mayer was the first observer who constructed a general 

 map of the moon in which the positions of the chief lunar spots were 

 laid down from actual measurements, and not from mere eye-drafts. 

 The intended publication of his lunar sketches at the end of the last 

 century was frustrated by the death of Lichtenberg, who had under- 

 taken it, and Mayer's smaller general map remained the only accessible 

 result of his selenographical labors. To the discussion of any questions 

 referring to physical changes on the moon's surface, the evidence which 

 may be derived from trustworthy sketches made at an early period is 

 obviously of considerable importance, and the publication of Mayer's 

 old sketches is therefore a welcome addition to the available sources of 

 information. There are forty sketches made between June, 1748, and 



