306 
difficult problems. On page 63 we are invited 
to think of a moving point as going from one 
position to the “next.” Two points thus next 
to each other form an infinitely small straight 
line. The two points are consecutive, with- 
out distance between them, and “may prac- 
tically be considered as one point.” No talk 
about limit: a curve is, for thought, composed 
of infinitely short straight lines. The term 
locus does not appear except incidentally as 
on page 84. But “if a point moves so as 
continually [not continuously] to change its 
direction from point to point, the line gener- 
ated is a curved line, or curve.” According 
to the highest mathematical standards, de- 
scriptive geometry has not attained, in Amer- 
ica, to the rank of a science. It is a tool. 
Judged as a work designed to teach the use 
of an important tool, Professor Bartlett’s book 
will render good service. But such books 
ought to get up-to-date in respect to logic, 
geometric spirit, conception and nomenclature. 
CoLUMBIA UNIVERSITY C. J. Krysrr 
Les Poissons Wealdiens de Bernissart. By 
Ramsey H. Traquair, M.D., LL.D., F.R.S. 
Extrait des Mémoires du Musée Royal 
d’Histoire Naturelle de Belgique, T. VI. 
Bruxelles. 1911. 4to. Pp. iv+65; 12 
pls. and 21 text figures. 
In this memoir Dr. Traquair—the dean of 
paleichthyologists—discusses the fishes of the 
Wealden, or basal Cretaceous, of Belgium. 
This formation, though known chiefly for fine 
skeletons of the dinosaur Jguanodon, contains 
also a highly interesting fish-fauna. This 
is remarkable for the fact that its species, 
though relatively few (sixteen), represent 
both the more archaic members of the group 
of ganoids as well as the quite modern teleosts. 
In discussing this fauna, therefore, Dr. Tra- 
quair has opportunity of reviewing at once 
such forms as Coccolepis, the last survivor 
of the Palzoniscide, as well as Leptolepis, 
the earliest of the clupeoids. 
The memoir is of necessity devoted mainly 
to systematic details; none the less broader 
questions, such as those of morphology, rela- 
tionship and geological distribution, are not 
SCIENCE 
[N.S. Vou. KXXXV. No. 895 
overlooked. And all these themes are treated 
with the author’s characteristic painstaking 
regard to fact. In short, the memoir is an ex- 
ample of what a systematic review of a fossil 
fauna should be. 
An interesting and very useful feature is 
the carefully drawn restorations, of which 
there are thirteen. Especially noteworthy are 
those of Coccolepis, Callopterus, Amiopsis, 
Mesodon (with new interpretations of the 
eranial elements) and Aethalion. These fig- 
ures are sure to follow the many others from 
the same hand, and become part of the stock 
in trade of all writers on ichthyology. 
The fauna of Bernissart, as a whole, is re- 
garded as fresh water. The chief evidence for 
this view is the entire absence of sharks from 
this formation, although the group is abun- 
dantly represented in other European rocks of 
equivalent age. 
To the friends of Dr. Traquair—and they 
are many, both in Europe and America—the 
publication of this memoir has an especial in- 
terest. For it shows the doctor, who is past 
his seventieth anniversary, still working away, 
with his old-time vigor and enthusiasm, in the 
field which he has done so much to advance. 
Ave Magister! Many be the years 
That lie before thee, thronged with busy hours!? 
L. HussaKor 
AMERICAN MUSEUM oF NATURAL HISTORY 
THE HARRIS TIDAL MACHINE 
THE Coast and Geodetic Survey has re- 
cently put in operation, after a thorough test, 
a new tide-predicting machine, which performs 
simultaneously all the operations of the Brit- 
ish or Thomson machine and of the first 
American machine invented by Professor 
Ferrel. As in the Thomson machine, the 
tidal curve is drawn from which the height of 
the tide at any time may be scaled off, but, 
in addition to this, the times of high and 
low water are marked upon its axis, and both 
the time and height of the tide, as well as the 
height of the water’s surface at any given 
1Dr. S. Weir Mitchell, ‘‘The Comfort of the 
Hills and Other Poems,’’ p. 95. New York, 1910. 
