284 PROCEEDINGS OF THE AMERICAN ACADEMY 



sonal examination. The latitude as given by Pentland, 16° S. for 

 the northern extremity of the Island of Titicaca, is very nearly cor- 

 rect, Capt. Guerrero and myself having taken several sextant observa- 

 tions off the northwest point of tlie island, which agreed quite closely 

 with Pentland's positions. The longitude of Puno, however, as given 

 by Pentland, 70*^ W., is j^robably not quite correct, and too far to the 

 eastward. The distance of Puno from the harbor of Mollendo being 

 only seven minutes in time, as ascertained by telegraph between the 

 two points, of course this is approximate ; while taking the longitudes 

 as given on the English admiralty map 73° 39' for Mollendo, as given 

 by Fitzroy, and 70"^ for Puno, by Pentland, the diiference of longi- 

 tude is somewhat greater, more than 3°. 



Mr. Garman and myself took more than sixty -five soundings, from 

 which a number were selected to represent the surface of the bottom. 

 The whole bottom of the lake in its deepest parts, and frequently quite 

 close to the shore, up to the point at which the myriophyllum and the 

 totora grow so plentifully in certain localities, is covered by a thick 

 bed of mud, the finest jjossible greenish black silt. This bed of mud 

 must have been several feet in thickness, to judge from the ease with 

 which the heavy sounding leads disappeared in it. It contained but 

 few fragments of shells, being almost always made up of pure fine 

 mud. It was only in a small number of localities near the shore, and 

 away from the mouth of any rivers, that occasional patches of sand 

 and of shelly or rocky bottom were found. In the lower lake, 

 however, the bottom was generally sandy, the water having deposited 

 the bulk of the matter held in suspense before reaching the Straits of 

 Tiquina. At the time of our visit to the lake, althougli during the 

 last jjart of the rainy season, when all the rivers pouring into the lake 

 were very high and turbid with the mud and materials they brought down 

 from the mountains, yet, a short distance from the shore, the surface 

 water was remarkably pure and clear. According to an analysis made 

 by Professor Raimondi of Lima, there is but a mere trace of saline sub- 

 stances, and not sufficiently large to affect the potability of the water. 

 Having an outlet to Lake Aullagas through the Desaguadero, there is 

 no chance for an accumulation of saline matter, while Lake Aullagas 

 is already, as I am told, somewhat saline, and the sink into which that 

 pours is quite saline. The unpleasant taste of the lake water near the 

 shore is due to the immense amount of decayed vegetable matter 

 abounding in the extensive fields of myriophyllum and of totora, 

 which line the shores for miles, and which e.xten 1 to a depth of from 

 six to seven fathoms. The totora fields are most extensive in Puno 



