198 
17 on structural features is also valuable. Mine 
waters also receive better treatment than they 
often do. But in his argument for ,the im- 
portance of ascending juvenile thermal waters 
one might have hoped to see a comparison of 
the analyses of waters! with those which would 
be obtained from the connate or meteoric 
waters stimulated in circulation by hot in- 
trusives. There is a lot of sodium carbonate 
and sulphate in the mine waters of many re- 
gions where “alkali” is also characteristic of 
the surface waters, while the mine waters of 
other districts are quite different. It may 
well be that we have a mixture of waters from 
more than one source, and while the author 
rightly attributes to precipitation by mixture 
of solutions an importance which is often 
overlooked, :yet it may have even greater im- 
portance. 
The range of reference is rather narrow, 
mainly, though by no means exclusively, to the 
western! United States. In that respect both 
of the other books are superior.. For in- 
stance in discussion of the class of zeolitic 
native copper deposits no reference is made 
to the ;work of Weed and Lewis on those of 
New Jersey, and one might think that 
Keweenaw Point was unique, except for a 
footnote reference to White River, Alaska. 
With regard to the Keweenawan deposits there 
are a number of minor slips (p. 3897). Copper 
veins are still of considerable importance at the 
Ahmeek and adjacent mines, nor was the cop- 
per obtained from veins formerly, nor at pres- 
ent, wholly or mainly sulphide. It is usually na- 
tive, sometimes the basic arsenide, and even in 
the Nonesuch lode one would hardly say that 
the ore was “chiefly ” chalcocite. The None- 
such mine saved only the native copper. It is 
noteworthy that jthere is no such systematic 
attempt to present diverging points of view 
fairly as is made by Ries. Compare for in- 
stance the treatment of oolitic iron ores in 
each. This is probably due to the origin of 
the book as a course of lectures. So, too, 
while Lawson is referred to, as to his western 
work, no reference is made to his Lake Su- 
perior work. Neither is Allen’s declaration 
that the Animakie is middle Huronian con- 
SCIENCE 
[N. S. Von, XLVIII. No. 1234 
sidered. The Keweenawan is classed without a 
question as pre-Cambrian. 
After the extensive treatment of ore deposits, 
iron, icopper, gold, silver, zinc and lead receive 
treatment in separate chapters, while all the 
rest of the substances are dismissed in the 
last hundred pages. 
Two relatively new terms are protore: “ low- 
grade metalliferous material not itself valu- 
able from which yaluable ore may be formed 
by superficial alteration and enrichment,” and 
the horsetail structure applied by Sales to di- 
vergent minor fractures. Both these seem to 
be useful. 
There is no list of illustrations. 
AurreD C. Lane 
Aquatic Microscopy. By Atrrep C. SToxEs. 
Fourth Edition. New York, John Wiley 
and Sons. 1918. Pp. 324. 
The new edition of this well-known guide 
for beginners retains the general features of 
the earlier editions. Chapter XII. of the 
third edition, “Some Common Objects worth 
Examining,” has been replaced by a “ Synopsis 
of the Preceding Chapters,’ which is a con- 
venient, brief key to the forms described in 
the book. Minor changes have been made in 
the text, various scientific names have been - 
modernized, and some of the keys have been 
extended. The book should continue to be a 
favorite, not only with the young microscopist 
for whom it is intended, but with many 
zoological students and teachers as well who 
desire to identify quickly and easily some of 
the commoner aquatic organisms. 
M. F. Guyer 
UNIVERSITY OF WISCONSIN 
SPECIAL ARTICLES 
ADAPTATION IN THE PHOTOSENSITIVITY OF 
CIONA INTESTINALIS 
I 
Ciona intestinalis of the Pacific Coast? re- 
1 These experiments, the details of which -will 
appear later, were performed at the Scripps In- 
stitution for Biological Research at La Jolla, Cali- 
fornia. My thanks are due to Dr. Ritter and his 
staff for the many courtesies shown me. 
