544 
low. But the busy man and the man without 
mathematical training must take the state- 
ments of the next 8 chapters, or 146 pages, on 
faith. The essential equations in the greatest 
abundance are there and their meanings ex- 
plained, but checking them all up would be no 
easy task. 
The general conclusions all this mathe- 
matical work leads to are given in a short 
chapter of only 6 pages, and in another place 
20 separate theses are proposed that should set 
many young men at work on problems that 
are both new and useful in applied mathe- 
matics. 
But, the “ practical” man will say, what’s 
the use of all this theory and all these mathe- 
matical equations? The answer in this case 
as in all similar cases is: To tell the practical 
man what to practise, what experiments are 
needed and what are not, what general type 
of machine is likely to succeed and what is 
certain to fail; to save him from needless 
blundering and to assure him of results and 
how to obtain them that he never did and 
never would even dream of. 
Professor Bryan’s book is especially adapted 
to the needs of advanced students in physics, 
applied mathematics and certain branches of 
engineering, and richly deserves a place in 
both mathematical and physical libraries. 
W. J. Humpnreys 
Non-Marine Mollusca of Patagonia. By 
Henry A. Pinsspry. Reports Princeton 
University Expeditions to Patagonia, Vol. 
Ii., Part V. 
This important work was issued in 1911, 
but there is nothing about the separate issue 
to indicate the date. It deals with the non- 
marine molluses of Tierra del Fuego and 
Patagonia as far north as the thirty-ninth 
parallel, and is most beautifully illustrated 
by colored and uncolored plates. Of certain 
families, all the South American forms are 
listed. At the end is given a most interesting 
discussion of the characteristics and origin 
of the South American Mollusca. 
The poverty of the Patagonian fauna in 
land snails is remarkable. Seven Endodon- 
SCIENCE 
[N.S. Vou. XXXV. No. 901 
tide and the two Zonitide have been de- 
scribed, all small. Their precise affinities are 
uncertain, from lack of knowledge of the in- 
ternal anatomy. A small slug has been re- 
ported, perhaps introduced. Swuccinea is repre- 
sented by several species, one of them 
abundant. No doubt other species will be dis- 
covered, but certainly no other part of the 
world, in a similar latitude, has such a 
meager representation of land shells. With 
the fresh-water snails it is somewhat different, 
the fauna not only containing a number of 
species of the families familiar in the north- 
ern hemisphere, but also a rich representation 
of the Chilinide, a family confined to the tem- 
perate and cold zones of South America. All 
the Chilinids east of the Andes are discussed, 
with four fine plates. Six colored plates are 
devoted to the Amnicolid genus Potamolithus, 
of which a complete revision is given. There 
is a complete list of the South American 
Spheriide, with descriptions of several 
species. Thus the work, while ostensibly a re- 
port on the Princeton collections, is in real- 
ity much more extensive and important than 
the title would suggest. 
All zoologists will be interested in the gen- 
eral discussion of the fauna. Dr. Pilsbry 
recognizes a Ccenogeic or northern group of 
families, and an Eogeie or southern group, 
the latter having “ occupied chiefly the Gond- 
wana continent, including a large part of 
South America, tropical and South Africa, 
and stretching in a great arch, possibly at no 
time perfect, to peninsular India and Aus- 
tralia.” It is in this second group that he 
would place the Mutelide, Ampullariide, 
Acavide, Bulimulide, Achatinidz, Strep- 
taxide, ete. With regard to Antarctica, it is 
shown that the non-marine molluscs, taken 
by themselves, indicate that: (1) “There is 
no evidence that Antarctica was ever an evo- 
lution or radiation center for non-marine 
mollusks, though there is some evidence show- 
ing that it served as a highway for migration.” 
(2) “There is some evidence of migration 
from South America to Australia, but at pres- 
ent no evidence of a counter movement to 
South America.” (8) “ Nothing in the dis- 
