GEOLOGY OF PERU—ADAMS. 409 
hill above the town of Cuzco, and expressed his opinion that the 
whole valley in which Cuzco les was occupied by a glacier. The 
evidence given for so great a glacier is not quite so complete as 
might be wished, at least its lowest limit should be determined. <Ac- 
cording to Duefias the elevation of the Rodadero is 3,900 meters; the 
present limit of perpetual snow in that region is at 4,300 meters, and 
Cuzco is at 3,450 meters. 
Undoubtedly the limit of perpetual snow was much lower during 
the glacial period. Just how much lower, is a question deserving of 
study. Raimondi has noted (1873) the occurrence of moraines much 
below the present snow line in the Cordillera Blanca. 
At many places near the snow fields abandoned cirques may be 
seen below the limits of the perpetual snow and the diminutive 
glaciers of the present time. The writer has studied the glacier 
beds and moraines in the vicinity of Poto to the north of Lake 
Titicaca in the Cordillera Oriental and has estimated that in the 
glacial period the ice fields extended about 2,500 feet lower than the 
present glaciers.” 
Recent elevation of the coast. 
OBERVATIONS AT SAN LORENZO ISLAND By DARWIN. 
In 1835 Darwin visited Peru and landed at Callao, but because of 
the troubled political condition he saw but little of the country. He 
reported finding on San Lorenzo Island, in front of the bay, three 
obscure terraces, the lower one of which, at a height of 85 feet above 
the sea, is covered by a bed a mile in length almost wholly composed 
of shells of 18 species now living in the adjoining sea. He found a 
bed of more weathered shells at an elevation of 170 feet. Among the 
shells at 85 feet above the sea he found some thread, plaited rushes, 
and the head of a stalk of Indian corn. From these facts he con- 
cludes that within the Indo-human period there has been an elevation 
of 85 feet. ['These observations by Darwin have been often quoted, 
and only last year an excursion composed of professors and students 
from the School of Mines at Lima visited the island to study these 
terraces, and failed to reach a definite opinion in regard to the value 
of Darwin’s conclusions. | 
OBSERVATIONS AT SAN LORENZO ISLAND BY DANA. 
Fortunately, the views of Darwin have been competently criticized 
by Dana, who (1840) visited the locality as a member of the Wilkes 
@J¥n northern Bolivia Arthur F. Wendt has observed that the glaciers of 
Illimani and Sorata have their lower termination at an elevation of about 
18,000 feet, and that the ancient glaciers reached down to 15,000 feet. (Proc. 
Amer. Inst. Mining Eng., 1890, vol. 19, p. 85.) Agassiz (1868), it will be 
remembered, regarded the clays and superficial deposits of the Amazon Valley 
as glacial deposits, but later recognized his error. 
