_ lation, or from 88,000 to 132,000 years. The combined age 
of both cones, therefore, would by this calculation be between 
96,000 and 143,000 years. It is with great hesitation that I 
question the conclusions of an European savant, made respecting 
s own country; but having twice examined these cones with 
great care, and followed the torrent a mile into the mountains 
to study its appearance and action, I cannot avoid the conclu- 
sion that there is a very singular mathematical error in estimat- 
ing the e of the cones, and an omission of several important 
geological facts which vitiate the whole calculation. ‘The nature 
of the mathematical error will be made obvious by a few facts. 
‘rectly quoted, he first derives his scale of from three and t > 
tenths to four inches increase per century from the superficial 
lay ers ar they are thinnest, and then applies it without mod- 
: | small, and exag- 
 gerates the total age. It is perfectly plain that the true method 
is to take the cubic contents of the strata whose age is known, 
and compare the amount with the cubic contents of the whole - 
cone; or, in plain la », if the annual rainfall and gravel 
