NATURE 
‘ferns 



themselves to a qualification test, is in order that these | water at the bottom,and I have pointed out that such a_ 
offices may not be the refuge for genteel incompetence, | 
but may be bestowed on the most fitting aspirant. We 
fear the above facts will show that the present system is 
not calculated in all cases to secure this end. 

THE GIBRALTAR CURRENT 
R. CROLL having stated (NATURB, August 17) 
that, taking my own data, and having “in regard 
to the Gibraltar current and Dr, C.’s general oceanic cir- 
culation, determined the absolute amount of those effects 
on which his circulation depends,” he has satisfied him- 
self by mathematical investigation “that the work of the 
resistances greatly exceeds the work of gravity, and that 
consequently there can be no such circulation as that for 
which Dr, C. contends,"—I think it well to point out that 
the question of the existence of such a circulation is not 
to be disposed of C the calculations of even such an ex- 
pert computer as Mr, Croll, but must be decided by the 
collection and comparison of facts ascertained by observa- 
tion and experiment. 
Now, as it happens that an opportunity has been re- 
cently afforded me by the Hydrographer to the Admiralty 
of carrying out, in conjunction with Captain Nares, of 
H.M.S, SRearwerter, a series of farther researches on 
the Gibraltar current, which place beyond all doubt the 
outflow of dense Mediterranean water into the Atlantic, 
over the “ridge » or “marine watershed” between Capes 
Trafalgar and Spartel, and beneath the surface-inflow of | 
Adantie water, | would submit (1) whether there must not 
be some fundamental fallacy in Mr, Croll’s computations | 
in regard to the Gibraltar current, and (2) whether this 
fallacy should not destroy all confidence in the infalli- 
bility with which Mr, Croll credits himself in regard to 
the general oceanic circulation, 
No one can be more ready than myself to admit that 
this last doctrine is at present only a hypothesis, resting 
on a very narrow basis of fact. But as this hypothesis 
has been accepted as probable by such great masters in 
bali science as Sir John Herschel and Sir William 
homson, and as the means of putting it to the test will 
be supplied by the Scientific Circumnayigation Expedition, 
which (1 have every reason to expect) will be fitted out by 
Her Majesty’s Government next year, I would venture to 
Suggest whether prudence does not dictate to the 
opponents of that doctrine, that they should either drop 
further discussion of it for the present, or that at any 
rate they should refrain from attempting to demonstrate 
its impossibility, 
The number of NATURE which contained Mr, Croll’s 
letter, having also given an account of the discussion 
which took place in the Physical Section of the British 
Association on a communication I made to it with 
reference to this subject, | may mention that my especial 
purpose in that communication was to obtain the judg- 
ment of the able physicists there assembled, as to a fun- 
damental question at issue between my friend, Prof, 
Wyville Thomson, and myself, namely, the arwse of that 
flow of polar water over the deepest parts of the ocean 
bottom, bringing down its temperature even under the 
equator to 3355, as to the fact of which we are in entire 
agreement, By my excellent colleague it is considered® | 
that this flow is due to an_indraught of polar water, oc- 
casioned by the surface efflux of equatonal water result- 
ing from the action of the Trade Winds. To myself (not 
professing more than an elementary knowledge of physics) 
it seemed probable, on the principle of “least action,” 
that the surface-water so removed would be replaced by 
an inflow from some other part of the oceame surface, 
that is, by a horizontal circulation, rather than by an up- 
rising of the whole subjacent mass, so as to draw in polar 


*See his Address on “The Distritation of Temperature in the North 
Atlantic,” Natuas, July ap, i 
, contains, first, original memoirs ; 
surface-replacement is known to take place in the case c 
the Gulf Stream, one portion of which directly return 
into the equatorial current, completing the shorter cir- 
culation, whilst the other has its complement in the Green- 
land, Labrador, and other polar surface-currents, of which 
the principal is traceable southwards nearly as far as the — 
exit of the Gulf Stream from the Narrows, thus complet-— 
ing the longer circulation, 
The correctness of this “common-sense” judgment 
was most emphatically affirmed, on the basis of profound — 
physical knowledge, by Sir William Thomson and Prof. 
Stokes. It was agreed by these high authorities that in — 
the open ocean the action of wind on the surface can 
never produce any other than a surface movement; the _ 
water propelled onwards from one part of the oceanic. 
area being replaced by a surface inflow from other 
It is, therefore, for my opponents to explain how, other- 
wise than by gravity, it happens that polar water finds 
itself at the depth of 2,000 fathoms under the equator. 
That the bottom-temperature of the equatorial area, if 
there were no movement of polar water towards the 
equator, would be at least 20° higher than it is, may be 
asserted without the least hesitation ; the temperature of 
the Mediterranean, which is cut off from communication 
with the lower stratum of the Atlantic, (being 54° at 
corresponding depths, 
It was agreed by Sir William Thomson and Prof. 
Stokes, that when a wind blows continuously into a loch 
or ford, so as to produce a rise of water at its head tothe 
| amount of 6, 8, or 10 feet, such an excess ot vertical pres- 
sure produces an outward under-current ; the evidence of 
such outflow being afforded by the continuance of the 
surface In-current at the rate of three or four miles per 
hour, without any further increase in the rise of water at 
the head of the loch, This exceptional case was advanced 
by Sir W. Thomson as strongly confirming my general 
principle, not as invalidating it; and I would therefore 
recommend Mr, Croll to test his method of investigaton 
by this ascertained fact, rather than spend his time in 
demonstrating the impossibility of what he may hereafter 
have to admit as no less certainly proved. 
WILLIAM B, CARPENTER 
H.M.S, Shearwerfer, Malta, 
Sept. 29 

SCIENCE IN ITALY 
[* NaTuRE for June 8, I sketched a short notice of 
same of the Italian scientific serials, among them the 
Annali di Chimica Applicata alla Medicina, published at 
Milan, With the commencement of the present 
the Gaseifa Chimica Jialiana has» been machel SE 
Palermo, The project of this publication originated in 
Florence with a society of Italian chemists, who met there 
in October last, and resolved to entrust the first year’s 
* direction » of the magazine to Prof, Stanilaus Cannizzaro 
of the University of Palermo, 
The Italian Chemical Gazette very nearly resembles the 
Feournal of the Chemical Society of Lender. Like this it 
second, translations or 
abstracts of the most important foreign chemical memoirs ; 
third, a review of technological chemistry, agricultural 
chemistry, and crystallography ; fourth, a summary of the 
principal chemical journals of Germany, England, and 
France ; fifth, miscellaneous notes that may be interesti 
to those who cultivate chemical science. It is published 
monthly, 
The most prominent, the longest, and most interesting 
of the original papers is by Prof. Cannizzaro; * Histori- 
cal notes and refiectians on the Application of the Atomic 
Theary to epee and on the Systems of ee for 
expressi e Constitution of Compounds. S — 
is cee in the number for January, April, and May, 

a 
aw 
