196 
and islands, by the investigations of the depths of the 
ocean, collections of natural history will be enlarged 
almost to infinity; and it will be harder and harder 
to place them in our museums, and to preserve them. 
Everywhere buildings begin to be insufficient; and if 
we were to stick to the old system, according to which 
a museum exhibits nearly all its objects, the large 
central depositories of natural history would grow to 
an enormous extent. The organization of the Cam- 
bridge museum tries to meet equally the demands of 
SCIENCE. 
[Vox. IIL, No. 54, 
modest existence of a learned man to a materially 
better-paying occupation. In this respect Europe is 
stillfar ahead. Circumstances, however, will change, 
together with the great development of North Amer- 
ica; and in some of the Eastern States an altera- 
tion can already be noticed. We must therefore 
keep our eyes open, if we do not wish the experience 
of having our young cousins across the ocean outstrip 
us in a field the thorough culture of which, so far, 
has been the glory of old Europe. 
Que ent 
: its 
mT 
18 
Fie. 3. — Batteries for Tissandier’s balloon. 
science and the wants of the public which comes for 
information; and in this sense I have called the 
Agassiz museum a model museum for the future. 
Besides the institutions here mentioned, there are 
in many other cities of the United States — as Chica- 
go, San Francisco, St. Louis, Cincinnati, Princeton, 
Baltimore, Charleston, Providence, etc. — smaller mu- 
seums of natural history. They are almost all sup- 
ported by societies or schools. There is, therefore, 
no lack of interest in scientific studies; nor is money 
wanting. But still the number of those is very small, 
who, out of pure enthusiasm for science, prefer the 
TISSANDIER’S ELECTRIC BALLOON.)—IL. 
As we have described our apparatus as a whole, 
we will now give some details concerning the various 
parts, and especially concerning the dynamo-electric 
motor and the bichromate of potassium battery, which 
was prepared with a view to our experiments. 
The motor is a Siemens new model machine, made 
at Paris especially for us, consisting of a bobbin very 
long in proportion to its diameter, and mounted on a 
light wood frame. This machine weighs only fifty- 
1 Concluded from No. 53. 
ey eG es 
