SOUTHERN CALIFORNIA ACADEMY OF SCIENCES. 117 



pey, in the British Channel, where the writer when a small boy 

 amused himself collecting fossil shark's teeth, fishes, turtles, birds, 

 crabs, lobsters, mollusks and other animal remains, found with 

 fossil fruits of unknown extinct palms and other trees, which all 

 occur there in a remarkable state of preservation. These fossils 

 in which the original substances have been replaced by iron pyr- 

 ites are in such abundance that they are collected on the sea shore 

 by the inhabitants and sold by the ton to the manufacturers of 

 sulphuric acid and sulphate of iron (copperas). 



These fossils afford abundant evidence of the material 

 changes in the topography and climate of the region in compara- 

 tively recent geologic times, and prove the former existence, dur- 

 ing the Eocene Period, of a large river which formed an estuary 

 near the present mouth of the river Thames, where the immense 

 amount of material representing tropical animals and plants were 

 deposited. 



The banks of this ancient river were lined by magnificent 

 palms, ferns, and other tropical plants, inhabited by curious birds, 

 reptiles and extinct mammals, while its waters teemed with sharks, 

 fishes and reptiles. 



"But suddenly, from causes yet unknown, 

 All Northern latitudes were clad with ice, 

 So tense the cold great lakes and rivers froze 

 In mass, and teeming lands were thus bereft 

 Of animated life, which perished there 

 In one vast frozen sepulchre " 



• FOSSIL WOOD. 



Among the most widely distributed of the relics of past 

 ages are fragments of the leaves, flowers, fruits and branches of 

 fossil plants, and the wood,. and sometimes the entire trunks of 

 trees are found in abundance in strata of the earth's crust. Va- 

 rious minerals have replaced the original substance, rendering 

 them practically proof against the destructive action of the ele- 

 ments. 



This substitution is so complete that the specific characters of 

 the plant or tree are perfectly preserved and the species may be 

 readily determined. 



The minerals which are the most common substitutes for 

 the original material are Silica in various forms ; Carbonate of 

 Lime; Carbon, and Sulphuret of Iron ("Iron Pyrites"), and the 

 substitution of pseudomorphism is so complete and perfect that, 

 thin sections prepared for the microscope present all the optical 

 characteristics and minute details of the living plants. Ores 

 of Copper and Iron, Native Sulphur, Sand, Silt, Salts of Lime, 

 and other mineral substances form casts in the moulds made by 



