276 W. J. MeGee—E lements in Orographic Displacement. 
eton from the plates alone. And yet with this faithfulness to 
the chief aim of the illustrations there is combined an artistic 
finish which has made each plate a kind of finished picture.” 
Professor Marsh’s volume on the Odontornithes stands almost 
if not quite alone among works on fossils, as regards the com- 
pleteness of the material described and figured, the paleonto- 
logical interest attaching to this material, and the importance 
of the biological conclusions drawn from it. As the first 
volume of the Memoirs of the Yale Museum, it gives a rich 
ise of what we may hope to see when the extensive 
collections at New Haven shall have been fully investigated. 
. BrRD GRINNELL. 
Art. XXXIL—On some Elements in Orographic Displacement ; 
by W. J. McGEr. 
essentially identical results would follow the most rigid analysis. 
The solid crust of the earth may be assumed to consist of 
three layers of equal thickness (which may be designated as ”, 
o, and p), but of density varying as 2d, 3d, and 4d respectively, 
resting upon a mobile substratum.* Tangential strain due to 
* The “critical shell” of Mr. King might be equivalent to such a mobile 
‘substratum. 
a 
