THE TRUCKEE AND HUMBOLDT VALLEYS. rri 
as minnows aud stickle-backs, to fresh water must be done 
gradually if we wish a happy result; in this process we have 
an example to follow, set by nature herself, for there are in- 
stances of bodies of what were once salt waters, so freshen- 
ing by degrees that they still retain seals and certain marine 
animals. We may find crabs in the Charles River at some 
distance above Cambridge, and they may be kept alive and 
in health for a length of time in the fresh-water aquarium. 
The system of artificial aération and that of producing an 
ebb. and flow in the marine aquarium have been practiced 
with success in large collections of aquaria. 
The value of the aquarium as a means of instruction can- 
not be overestimated, affording as it does the opportunity 
of studying the habits of aquatic animals in a manner attain- 
able by no other means, and giving to all an inducement to 
pursue further the study of natural history which will be a 
pleasure throughout life. 
* 
A SKETCH OF THE TRUCKEE AND HUMBOLDT 
VALLEYS. 
BY W. W. BAILEY. 
SiwcE the opening of the Pacific Railroad all haye had 
their attention more or less turned to that vast region lying 
between the Sierra Nevada and the Rocky Mountains. It is 
known as the Great Basin ; but if, misled by the name, we con- 
ceive merely of a boundless valley, more or less desolate, we 
shall arrive at a somewhat erroneous conclusion. It is indeed 
a depression between the two giant ranges of the continent, 
but traversing this are successive parallel mountain chains 
. with a north and south trend, and only inferior in altitude to 
the Roeky Mountains and the Sierra. Indeed, according to 
our eastern notions, the whole so-called basin is but a broad 
