44 J. LeConte—Extinct Volcanoes about LakeMono. 
outer slope of the moraine, when I saw it, in 1872, wasjust at the — 
limit of stabihty—the least disturbance caused the fragments to 
roll down. It would seem therefore that the moraine is being _ 
pushed slowly forward. Whether the same is true still I know _ 
not. 
feet vertical, on which for ages there has been too much winter 
snow to allow the growth of timber. In the timber region bor- 
dering the bare region there are many trees which have two — 
hundred and fifty annual rings. These trees have therefore — 
n growing securely for two hundred and fifty years. But — 
since 1860 the snow has so advanced upon the timber region | 
that these great trees are being destroyed by avalanches. It — 
would seem therefore that not only has there been recent ad- — 
vance, but that it is the first advance for two hundred and fifty _ 
ars. 
Se 
e 
The rise of the lakes in the desert region is therefore un- — 
seobtediy the result of a climatic cycle. But whether the cycle — 
x5 
* King, in his recent volume on Systematic Geology of the 40th parallel, p. 477, 
says that all Mr. Muir’s living glaciers of the Sierra are only moving snow-fields 
well known to the California surveyors. He then quotes Agassiz defining the 
istinction between such moving névés or snow-fields and true glaciers. This dis- 
tinction according 
bosom and thus to form a moraine. Now, it is but justice to Mr. Muir to say — 
that the ice in the Lyell-Cirque does bear e rock fragments on its surface and 
accumulate at its lower limit as a ect terminal morai niz 
however, the fact that this ice mass does not emerge 
m “ Ancient Gla ff 
in 
from its native cirque, I 
the Sierra” (this Journal v, 325), 
ciers 0. 
