July 4, 1902.] 



SCIENCE. 



29 



brief, that in the absence of a proper con- 

 trolling musculature, any such interlockini? 

 as that described could be brought about only 

 by accident; that habitual interlocking would 

 bring about, furthermore, conspicuous wear- 

 ing of the vane in the areas of contact, a phe- 

 nomenon not observed in emarginate prima- 

 ries; and that he concluded from his extensive 

 studies upon feathers and feather structure, 

 that habitu.al interlocking did not take place. 

 Mr. Frank Chapman, with a series of fine lan- 

 tern slides of birds in actual flight, demon- 

 strated that in some soaring birds, at least, 

 which possess emarginate primaries, these 

 feathers are certainly spread and not inter- 

 locked. Mr. Chapman agreed with Dr. 

 Dwight that the facts tend to support Allen's 

 theory of the origin of emargination, namely, 

 that aerial friction wears down the web ; and 

 that no such function is to be attributed to 

 emarginate primaries such as that ascribed 

 by Mr. Trowbridge. Prolonged discussion fol- 

 lowed, participated in by Mr. Trowbridge, Dr. 

 Dwight, Mr. Chapman, Professor Dean, Pro- 

 fessor Crampton and others. 



Henry E. Crampton, 



Secretary. 



SECTION OP ASTRONOMY, PHYSICS AND CHEMISTRY. 



At the April meeting of the Section Mr. 

 Percival Lowell gave a very interesting paper 

 on 'Modern Mars,' based on a series of maps 

 of Mars. 



1. Map-making of Mars began with Beer 

 and Miidler in 1840. Since then many charts 

 have been constructed of the planet. Some 

 of these are so old as to have been more or 

 less forgotten, some so new as not yet to be 

 known. Collection and comparison of such of 

 these maps as have marked advances in the 

 subject lead to some not uninteresting conclu- 

 sions. Such are presented in the accompany- 

 ing series. 



2. The series consists of twelve maps. 



I. Beer and Miidler 1840 



II. Kaiser 18G4 



III. Dawes by Proetor 1867 



IV. Resume by Flammarion 1876 



V. Sehiaparelli 1877 



VI. " 1879 



VII. Sehiaparelli 1882 



VIII. " 1884 



IX. Lowell 1894 



X. " 1897 



XI. " 1899 



XII. " 1901 



3. These maps fall naturally into three 

 groups, dividing the history of areography 

 into as many stages. 



I. Those from 1840-1877 

 II. Those from 1877-1892 

 III. Those from 1892-1902 



4. The maps of the first group are charac- 

 terized by large patches of light and dark 

 areas. Maps I.-IV. show these patches, and 

 by their agreement prove that the patches are 

 permanent in place. For the maps are the 

 work of different observers made at different 

 epochs of time. 



5. The maps of the second group are dis- 

 tinguished by a network of fine, straight lines 

 covering the bright areas of the disk, the 

 'canals' of Mars. This was the work of 

 Sehiaparelli. 



6. The maps of the third group are differ- 

 entiated by a similar system of 'canals'" in 

 the dark regions. This is the work since 

 Sehiaparelli. It has resulted in a complete 

 change in the belief as to the character of 

 these 'seas'; the permanency of the lines 

 showing that the background must be land, 

 not water. 



7. Inspection of the series results in three 

 deductions : 



I. That the whole series are in fundamental 

 agreement. 



The basic features appear directly through- 

 out the first period and as a groundwork iipou 

 which subsequently discovered detail is im- 

 printed in the second and third. 



8. The second deduction from these data is : 



II. That the almost inconceivable regularity 

 in the 'canals' was an evolution in percep- 

 tion forced upon Sehiaparelli by the objects 

 themselves; not a feature imparted by him to 

 them. 



His first map, in 1877, showed them as 

 arms or inlets of the sea penetrating the con- 

 tinent to great distances, but not character- 

 ized by remarkable regularity of form. His 



