286 PROCEEDINGS OF THE AMERICAN ACADEMY 



the bottom, even at the greatest depth (154 fathoms), was not more 

 than from 3 to 4 degrees. The lowest temperature of the bottom 

 was only 51°, the general temperature varying from 54 to 55^; while 

 the surface temperature ranged from 53 to 59°, the greater part of 

 the time 56 to 57° Falir. 



We used the ordinary deep-sea thermometer of Miller Casella, 

 kindly loaned to me by Captain Patterson of the United-States Coast 

 Survey. As is well known, deep-sea observations show that the effect 

 of the sun does not extend in the ocean much bej'ond 50 fathoms; but, 

 in a closed basin like this, at so great an altitude, the effect of the direct 

 rays of the sun passing through so little atmosphere is very great. 

 It must be remembered, that, even in the winter months of that re- 

 gion (the dry season), the sun never goes farther north than 52°, and 

 that only for a short time ; and that, in the summer months (the rainy 

 season), it is nearly vertical the greater jiart of the time. The water, 

 of course, retauis its heat readily, and, even in summer, is but little 

 cooler than the surrounding air, which becomes ver}' rapidly chilled by 

 the least cloud interposing between it and the sun. It is a very com- 

 mon thing for the thermometer to rise or fall eight or nine degrees in 

 as many minutes from the effect of the sudden appearance or disap- 

 pearance oi the sun. Ice is said to form only in small quantities 

 along the shores or shallow places : this is easily imagined when we 

 take into account the immense body of water which must be cooled, 

 120 miles long by 30 wide, and an average depth of about 100 fath- 

 oms ; the surface of the lake, even in winter, receiving a large amount 

 of heat by absorption, although the air itself is uncomfortably cold. 

 We find here, as is the case in many other sheets of water com- 

 paratively isolated, but few S})ecies, and these peculiar to the lake. 

 We find at this great elevation a condition of things reminding us of 

 the marine life of arctic regions, — a great abundance of specimens, 

 with a comparatively small number of species ; the shoals of Orestias 

 and Siluroids, which are seen in certain localities, agree with the ac- 

 counts we have of the swarms of fishes and other animals haunting the 

 arctic realms. Still there are peculiar physical conditions of the bot- 

 tom of the lake, the immense deposits of mud formed by the settling 

 of the silt brought down annually by the mountain-streams, the great 

 elevation of the lake, the high temperature of the water ; all of 

 which causes should tend to specialize to a remarkable degree the 

 genera found to thrive in such a condition of things. We find, how- 

 ever, no such specialization brought about among* the fishes : on the 

 contrary, their isolation, even while living under such peculiar physical 



