38 ANNUAL ADDRESS, MDCCCLXXIII. 



extensive portions of the continent of Europe, Asia, and 

 Africa at that time ? The nummulites were marine and 

 lived and died in the sea ; consequently the sea was 

 moving over a flat expanse of the earth's surface which 

 is now marked by the great mountain ranges of the Alps, 

 Pyrenees, Carpathians, and Himalayas. Sir C. Lyell says 

 these mountains could have had no existence till after 

 the middle eocene period, the antiquity of which is, as I 

 have just stated, but trifling when compared to that of 

 the Silurian or carboniferous age. " How comparatively 

 modern then," observes Sir C. Lyell, " is the date to 

 which some of the greatest revolutions in the physical 

 geography of Europe, Asia, and North Africa must be 

 referred !" 



It is said that ordinary limestone intensely heated in 

 closed vessels assumes the crystalline form. This must 

 of course be without access of air, and under circum- 

 stances which prevent the escape of carbonic acid. The 

 saccharoid, white crystalline, or statuary marble of Italy 

 is said to be the result of this action. 



Between the middle eocene period and the present 

 there have been formed, as far as we at present know, 

 no limestones of like magnitude. They may be briefly 

 enumerated as follows : The Bembridge series of lime- 

 stones, some of which were formed in fresh and brackish 

 water, because they contain fresh water fossils. They are 

 of upper eocene date. The Sicilian limestones are of 

 pliocene age : they cover half the island of Sicily. These 

 bring us to limestones of the recent or human period, 

 and as I before stated each great period had its limestones, 

 the same may be said of the present, which is as much 

 a geologic period as any of its predecessors. Wherever 



