122 SCIENCE SKETCHES. 
broken, — as in New York, in Pennsylvania, and in 
Georgia there are several streams which pass 
through it or around it. The much greater age of 
the Alleghany chain, as compared with the Rocky 
Mountains, seems not to be an element of any 
importance in this connection. Of the fish which 
cross this chain, the most prominent is the Brook 
Trout,! which is found in all suitable waters from 
Hudson’s Bay to the head of the Chattahoochee. 
A few other species are locally found in the head- 
waters of certain streams on opposite sides of the 
range. An example of this is the little red “ Fall- 
fish,’ ? found only in the mountain tributaries of 
the Savannah and the Tennessee. We may sup- 
pose the same agencies to have assisted these 
species that we have imagined in the case of the 
Rocky Mountain Trout, and such agencies were 
doubtless more operative in the times imme- 
diately following the glacial epoch than they are 
now. Professor Cope calls attention also to the 
numerous caverns existing in these mountains, as 
a sufficient medium for the transfer of many spe- 
cies. I doubt whether the main chains of the Blue 
Ridge or the Great Smoky can be crossed in that 
way, though such channels are not rare in the sub- 
carboniferous limestones of the Cumberland range. 
The passage of species from stream to stream 
along the Atlantic slope deserves a moment’s 
notice. It is, under present conditions, impos- 
sible for any mountain or upland fish, as the Trout 
or the Miller’s Thumb,” to cross from the Potomac 
1 Salvelinus fontinalis. 2 Notropis rubricroceus Cope. 
3 Cottus richardsoni Agassiz. 
