226 



LOWELL — AREOGEAPHY. 



[April 4, 



because contemporaneous ones included practically all their discov- 

 eries with additions. Of these, Cerulli's maps of 1896-97 and 

 189S-99 and Flammarion's of 1900-01 deserve special mention. 

 The omitted maps confirm, not invalidate, the conclusions here 

 drawn. 



4. Twelve maps constitute the series. Of these the ordering 

 chronologically runs thus : 



Mercator's projection is used in all the maps. The zero meridian 

 is in the same point on the planet in all except Kaiser's, though 

 that meridian does not always fall on the same part of the plate, 

 being in I, IX, X, XI and XII on the extreme left, in III, IV, V, 

 VI, VII and VIII in the centre. Beer and Madler's map is given 

 by Flammarion on a stereographic projection which, for the sake of 

 inclusion in the present series from its age and chronological im- 

 portance, has been changed to Mercator's. All other circumpolar 

 projections have been omitted. 



5. It will be seen from inspection of the maps, and would be 

 simply corroborated by further additions to the list, that increase 

 in our knowledge of the surface of Mars falls naturally into four 

 divisions or stages of development. The first of these is pre-carto- 

 graphic ; the second extends from 1840 to 1877; the third from 1877 

 to 1892; the fourth from 1892 to the present day. The first three 

 of these divisions correspond to those given in Flammarion's La 

 Planeie Mars. The fourth is since the publication of that bock. 



6. Near the end of the several periods are observations which 

 mark the dawn of the next to come, making as they do adumbra- 

 tion of phenomena clearly to be revealed in the succeeding stage. 

 Though not themselves the detection of details which characterize 



