248 Notices of Books. (April, 
lower level? Is it not evident that the sweeping assertion that 
differences of level will be restored by surface currents is a 
mistake? The course of currents, as the level is being restored, 
clearly depends upon the relative specific gravity of the water at 
the different levels. The heavier water will form the under 
current, and the lighter the upper, regardless as to which may be 
at the higher or lower level; and, if there be no difference of 
specific gravity, the level will be restored by a tidal movement 
forming a current through any narrow channel intervening, but 
not an upper rather than an under current. The systems of 
upper and under currents through the Straits of Gibraltar and 
the Sound are clearly the result of differences in specific gravity, 
as explained by Captain Maury’s theory, which had better be left 
in its origifal simplicity, for this modification with which 
Dr. Carpenter has attempted to encumber it is not an im- 
provement, but an erroneous complication.” 
Here we have the vulnerable point of Dr. Carpenter’s modified 
resuscitation of the old theory of oceanic circulation clearly — 
indicated, and a home-thrust of clear, sound reasoning fairly 
delivered through it. As this point is the very heart of Dr. 
Carpenter’s contribution to the subject, the thrust is fatal. It is 
followed by further and equally clear and able discussion of the 
details of Dr. Carpenter’s arguments, and of the theories off 
Maury, Rennell, Herschel, &c. This chapter xx. of Mr. Jordan’s 
book is really excellent, and worthy of careful reading, but we 
fear that it will not receive the attention it deserves, on account of 
the bad impression or prejudice which the author’s fundamental 
physical errors must induce. 
Cosmical theories are always dangerous, and their proprietors 
are always subject to a greater or lesser amount of martyrdom. 
Even if the theory is sound, its owner must die in order to obtain 
its acceptance; and if it is wrong, as usually happens, it is” 
liable to insinuate itself amidst all his sounder thoughts and 
positive researches, and poison or intoxicate his common sensé 
itself. Even if he has the exceptional strength of mind necessary 
for keeping his great theory from this sort of usurpation, he is 
a suspected visionary, and his most sober speculations are 
unnoticed.” We fear that Mr. Jordan will not escape these perils. 
Outlines of Natural History for Beginners. Being Descrip- 
tions of a Progressive Series of Zoological Types. By 
H. AtiteyNnE Nicnorson, M.D., D.Sc., M.A., PhD 
F.R.S.E., &c. London : Blackwood and Sons. ; 
Tuis is a clearly-written, unpretending sketch of the subject 
which it treats, and well adapted to its object, viz., to assist the 
teaching of zoology in schools. The mode of presenting the 
