674 
NATURE 
[AucusT 29, 1912 
tion is directed to the simple, but not generally 
known, method of slightly revolving the upper Nicol 
when in or near the position of extinction. 
The last chapter, on the optic axial angle, is in 
many ways the most interesting. It is now possible 
to obtain determinations in cases that would have 
been abandoned as hopeless a few years ago. When 
both axes emerge in the field of view the angle is 
usually measured by means of a linear scale in the 
eyepiece; Dr. Wright points out that, owing to the 
distortion introduced in the interference figure by the 
lens system the Mallard constant does not usually 
hold, and it is safer to calibrate the scale. Prof. 
Becke, with characteristic ingenuity, has recently 
shown that by mapping the brush in various posi- 
tions a remarkably accurate value of the optic axial 
angle is possible, even when only one ‘“‘eye”’ is 
visible; the method is fully explained and illustrated. 
For such work Dr. Wright uses a double micrometer 
eyepiece, but admits that a cross-ruled scale in the 
eyepiece is equally effective, a device that has been 
in use some years. Dr. Wright recommends for 
graphical work the little known Postel projection, in 
which the eye is situated at such a distance from 
the sphere that the distortion in polar directions is 
reduced to a minimum, and in tangential directions 
does not exceed the ratio of 7/2; the awkwardness 
of the shapes of the great and small circles, however, 
militates against its use. 
Prof. Fedorow’s universal stage, the invention of 
which placed an invaluable weapon in the hands of 
petrologists, and enables them to measure the angle 
between the optic axes and determine their positions 
with respect to the section, even when no ‘‘eye”’ is 
visible, is also fully discussed. At the close of the 
chapter Dr. Wright very carefully considers the 
accuracy of which the several methods are capable. 
Some novel diagrams will be found on the plates at 
the end of the book; neither of the diagrams repre- 
senting the equation sini=nsinr is, however, as 
simple as the graph devised by Mr. Hutchinson, in 
which the sines of the angles are taken as co- 
ordinates. An excellent index greatly adds to the 
value of the volume. 
SMITHSONIAN EXPEDITIONS. 
pe Smithsonian Institution has just issued a 
pamphlet describing, in part, the expeditions 
which it has organised or participated in during the 
field seasons of 1910-11, covering a wide variety of 
investigations conducted both in the United States 
and abroad. During the past two years the institution 
has been represented in eighteen different exploration 
and field parties. The scope of these activities has 
been world-wide, but more recently especial attention 
has been directed to Africa and the Panama Canal 
Zone. 
Unfortunately, as the regular resources of the 
institution are not sufficient to carry on extensive 
field explorations, it is often compelled to confine its 
efforts to investigations of limited scope, but of such 
a nature as to bear directly on the progress of science. 
In this connection it has been fortunate in securing 
the cooperation of a number of public-spirited citizens 
and scientific institutions, as well as several branches 
of the United States Government. 
The Smithsonian African Expedition had scarcely 
returned from the field when the institution received 
invitations to participate in two others, organised to 
explore the same general region. The first was Mr. 
Paul J. Rainey’s hunting trip to British East Africa 
and southern Abyssinia, where Mr. Rainey especially 
arranged to hunt lions with a paclx of American fox- 
NO. 2235, VOL. 89| 
hounds. The natural history collections that might 
be secured were offered to the Smithsonian Institu- 
tion, provided an expert field naturalist be sent to 
accompany him and prepare such of the game 
collected as was desired for exhibition or scientific 
study. Mr. Edmund Heller, who had accompanied 
the Smithsonian African Expedition in such a 
capacity, was selected, and departed with Mr. Rainey 
in February, 1911. The collection made has been 
estimated to contain some 4700 skins of mammals, 
together with many birds, reptiles, &c., and supple- 
ments the present African collection to a great extent. 
Nearly all of the material is from localities not 
covered by the earlier expeditions, and some of it 
comes from points never before visited by naturalists. 
The other natural history expedition was that of 
Mr. Childs Frick, of New York, whose object was to 
secure a collection of animals from the territory lying 
to the north of the regions visited by the earlier 
Smithsonian expedition and that of Mr. Rainey, 
covering at the same time certain parts of Abyssinia, 
northern British East Africa, and the country lying 
about Lake Rudolf. As naturalist of this party, Dr. 
Edgar A. Mearns, of the Smithsonian African Ex- 
pedition, was chosen. A portion of the collection of 
birds is to be donated to the Smithsonian Institution 
by Mr. Frick, and already several hundred specimens 
have been received. 
During the summer of 1911, Mr. Charles G. Abbot, 
director of the Smithsonian Astrophysical Observa- 
tory, and Prof. F. P. Brackett, of Pomona College, 
California, made a series of observations on the radia- 
tion of the sun at Bassour, a small town about sixty 
miles south-west of Algiers, and secured a large 
amount of data for comparison with simultaneous 
observations taken by Mr. L. B. Aldrich at the 
Smithsonian observatory station on Mt. Wilson, 
California. 
An expedition to South America, for the purpose of 
studying the material relating to the antiquity of man 
in that region, was conducted by Dr. Ales Hrdlicka, 
curator of physical anthropology, United States 
National Museum, and Mr. Bailey Willis, of the U.S. 
Geological Survey. The éxpedition collected many 
interesting geological, paleontological, and anthropo- 
logical specimens, which have been turned over to 
the National Museum for identification and descrip- 
tion, but the evidence gathered does not seem to 
sustain a large part of the claims regarding the 
antiquity of man in that region, which had been 
previously asserted by various authors. 
While in this part of the continent, Dr. Hrdlicka 
also visited the ruins of the city and temples of 
Pachacamac, Peru, where he made personal re- 
searches and studies in archzology and ethnology. 
His complete report on the antiquity of man in South 
America is made in Bulletin 52 of the Bureau of 
American Ethnology, now in press. 
In t910 the institution organised a_ biological 
survey of the Panama Canal Zone, with the coopera- 
tion of the Departments of State, Agriculture, Com- 
merce and Labour, and War. At first it was intended 
to confine the collections to the Canal Zone proper, 
but as the natural and floral areas extended to the 
north and south of this region, it was decided to 
carry the work into the Republic of Panama, a step 
which met with the hearty approval of that Republic. 
The worl: accomplished during the season of 1t910 and 
tg1r related to vertebrate animals, land and fresh- 
water molluscs, and plants, including flowering 
plants, grasses, and ferns. . 
Another expedition in which the institution co- 
operated was that organised by the United States 
Bureau of Fisheries and the American Museum of 
