366 TRANS. ST. LOUIS ACAD. SCIENCE. 



hours flowed back upon itself. For many miles, long zig-zag fis- 

 sures and yawning chasms were opened, large tracts of land sank 

 down and lakes and pools of water now fill the openings, over 

 which as we sail, far down in the deep, still water, may be seen 

 the ghostly branches of the sunken forests. Possibly some similar 

 catastrophe suddenly changed the course of the river and caused 

 its bed to become a vast malarious swamp, rendering the whole 

 region sickly and almost uninhabitable as it is to-day. The ap- 

 pearance of these remains would favor the idea that they were 

 suddenly abandoned. The chronological question may be a sealed 

 book which no man can open ; and the speculations thus briefly 

 indulged in may possibly — if they have no other value — indicate 

 the direction in which we may look with some signs of promise for 

 those facts which shall shed further light upon the life and times 

 of this mysterious race. 



Age of our Porphyries* 

 By G. C. Broadhead. 



In the American Naturalist of April, 1S75, Prof. T. Sterry 

 Hunt says, " The porphyries of Southeast Missouri seem to be 

 identical with those of Lynn, Saugus, Marblehead, anil Newbury- 

 port, Mass., which are traced thence along the coast of Maine and 

 New Brunswick, and are well developed about Passamaquoddy 

 Bay, where they occasionally contain small deposits of iron ore." 

 They are also compared with the rocks of the north shore of Lake 

 Superior, and are regarded as Huronian. On the coast of New 

 Brunswick they are intimately associated and interstratified with 

 schistose rocks, supposed to be of Huronian age. 



On p. 187 of his Chemical a?id Geological Essays, Dr. Hunt 

 says, "they present great uniformity of type, though in every 

 place subject to variations from a compact jaspery rock to a more 

 or less coarsely granular variety, all of which are often porphy- 

 rinic from the presence of feldspar crystals, and sometimes include 

 grains or crystals of quartz. In color they are generally some 

 shade of red, varying from flesh-red to purple, pale yellow, green- 

 ish, or black. On the coast, these rocks are distinctly stratified, 



