Fan, 26, 1871 | 

NATURE 
247 

balances the difference of pressures. At that height it remains, 
and no further movement takes place, so long as the relative 
pressures remain the same. A fluctuation of the pressures will 
give rise to alternate ingoing or outgoing currents, but a con- 
tinuous stream in one direction can only be produced by a con- 
tinuous increase or decrease of one or the other pressure. 
But independently of the equilibrium, which must, so far as 
the pressure is concerned, be established, the difference of level 
caused by these differences of pressure is extremely trifling. The 
barometric difference between the patch of high pressure in lati- 
tude 30° and the equator is about ;%;ths of an inch, or equivalent 
to a column of water 4 inches in length. A difference in level 
of 4 inches in 1,800 miles can scarcely under any circumstances 
give rise to a current of twenty miles an hour. 
J. K. Laucuton 
Royal Naval College, Portsmouth, Jan. 23 

Ir is singular that diversity of opinion should still exist as to 
whether ocean currents are due to the impulse of the winds, or 
to difference of specific gravity. That ocean currents are not 
caused by difference of specific gravity between the waters of 
equatorial and polar regions can be proved, as the amount of 
force from this cause acting on the ocean to produce a current, 
can be readily calculated. 
Assuming, which is not the%case, that difference in saltness be- 
tween the water of equatorial and polar regions does not in any wad 
tend to neutralise theeffect resulting from difference of temperature, 
in other words, that the sea in polar regions is as salt as the sea 
in equatorial regions, it can be shown that the force resulting 
from the difference of temperature, tending to produce a current 
towards the poles, amounts to only , 504090 of that of gravity. 
For example, the force impelling a cubic foot (64lb.) of sea 
water at the surface of the ocean towards the poles is scarcely 
equal to the weight of one-fourth of a grain." A force so infini- 
tesimal, acting on a fluid even so perfect as water, can produce 
absolutely no motion. M. Dubuat found by direct experiment 
that it requires a force four times greater than the above to pro- 
duce even sensible motion. . 
Ocean currents are due alone to the impulse of the wind. In 
the latter half of my paper on the Cause of Ocean Currents, 
which will shortly appear in the Philosophical Magazine, I hope 
to be able to show that the objections to this theory are founded 
upon misconceptions regarding the way in which winds produce 
the great system of oceanic circulation. 
JAMES CROLL 
Dr. Frankland’s Experiments 
In last week’s NATURE Dr. Frankland describes some ex- 
periments, apparently under the impression that they were 
similar to one (No. 20) published by me in NATURE, No. 36, p. 200. 
The results which he obtained were in reality totally different 
from those which I obtained, although those who read Dr. 
Frankland’s communication are lead to believe that the results 
were almost wholly similar. The inference to be drawn from 
what he has written is that we differ merely as regards the 
interpretation of the nature of what was seen. 
Dr. Frankland says he made use of tubes of ‘‘ hard Bohemian 
glass,” and that, on examining them ‘‘ when they came out of 
the digester, ,it was evident that the zzferior walls of the glass 
tubes had been corroded by the enclosed fluid.” After a time the 
“liquid in all the tubes became more or less turbid, and, in some 
cases, a small quantity of a light flocculent precipitate subsided 
to the bottom.” After five months two of the tubes, which ex- 
hibited ‘‘the greatest turbidity,” were selected for examination, 
and the ‘“‘flocculent sediment” in the tubes was more especially 
subjected to a careful microscopical examination. This scrutiny 
was conducted by Professors Frankland and Huxley and Mr, 
Busk. Dr. Frankland then says: ‘‘So far as the optical ap- 
pearances presented by the sediment go, they may be appro- 
priately described in the terms which Dr. Bastian applied to the 
matter found by him in a solution of like composition, and 
similarly treated.” 
Now, that any real similarity did exist, I feel most strongly 
inclined to doubt, because the solution examined was not similar 
in constitution to my own, and because no such ‘‘ flocculent 
sediment,” as that to which Dr, Frankland alludes, ever existed 
in my flask. 
In the experiment of mine to which reference is made, the 
precise quantities of carbonate ofammonia and phosphate of soda 
* Philosophical Magazine for October 1870, p, 249. 



employed are not known. In this first experiment the ingre- 
dients were not weighed, although, subsequently, solutions have 
been prepared for me of the strength which Dr, Frankland 
names. 
Then, although my tube with its contained solution was ex- 
posed to the same temperature as that employed by Dr. Frank- 
land, its internal walls were not in the least corroded, and no 
““flocculent sediment ” appeared in the solution. And, in addi- 
tion, two other tubes which were prepared for me by Dr. Frank- 
land (which did contain solutions of the same strength as those 
which he employed) have not had their transparency in the least 
impaired, although they were submitted to precisely the same 
temperature ; neither have they showna trace of the “ flocculent 
sediment” previously mentioned. Seeing, however, that in one 
experiment (May 11th), with a solution of the same strength, a 
tube of English glass was employed by Dr. Frankland’s assistant, 
and that the internal walls of this tube were corroded ; and 
seeing, moreover, that a ‘‘flocculent sediment ” did form also in 
this particular tube of mine, I cannot help fancying that Dr. 
Frankland may be mistaken as to the nature of the glass employed 
in his experiments. If, as in this experiment of mine, it was 
really English glass instead of hard Bohemian, almost the whole 
of the small quantity of phosphoric acid originally in the solution 
would probably haye been deposited in the form of an insoluble 
phosphate of lead, and thus the character of the solution would 
have been entirely changed. ; 
In my previously published experiment the fluid was examined 
at the end of thirty days. ‘* When this flask was received from 
Dr. Frankland, the fluid was somewhat whitish and clouded. 
During the last ten days a thin pellicle had been seen gradually 
accumulating on its surface, and in the latter four or five days 
this increased much in thickness, and gradually assumed a dis- 
tinct mucoid appearance. The fluid itself was tolerably clear, 
though an apparent turbidity was given by the presence of a fine 
whitish deposit on the sides of the glass. When the flask was 
opened the reaction of the fluid was found to be #eutral. Por- 
tions of the Ze//icle were at once transferred to a glass microscope 
slip,” &c. (NATURE, No. 36, p. 200.) In portions of this pellicle 
were found the “‘ five spherical or ovoid spores,” upon the finding 
of which alone I laid any stress as indicative of the presence of 
living things. The presence of mere particles having a move- 
ment indistinguishable from Brownian movements, has never 
been adduced by me as evidence that living things had been 
evolved in a solution, although the representations of others 
would lead the public to believe that I have done so. 
In the face of these differences, therefore, I was somewhat 
surprised at the intimations contained in Dr. Frankland’s letter. 
He believes, and would lead your readers to believe also, that the 
microscopical appearances presented by the ‘‘flocculent sedi- 
ment” and eérés of corroded glass obtained from his tubes were 
similar to the microscopical appearances of a fel/icle obtained by 
me from a tube in which there had been no corrosion. This, 
however, I am the less inclined to believe, because I also have 
had the opportunity of examining a flocculent sediment and adébris 
of corroded glass from a tube previously referred to, which was 
opened on October 21, and in which also no living things were 
found. Microscopical specimens of the “ pellicle” and of the 
‘sediment ” are now in my possession. 
Perhaps I may venture to recommend Dr. Frankland to 
destroy the other two tubes which are corroded, as being worth- 
less, and to hope that, in any future experiments, he will subse- 
quently expose his fluids to a somewhat higher temperature, and 
also, before immersing his experimental tubes in any fluids, that 
he will thoroughly satisfy himself as to the transparency of such 
fluids to the actinic orchemical rays of light. We are informed 
that his tubes were ‘‘exposed to bright diffused daylight, and 
sometimes to sunlight,” but any amount of exposure to light 
would be more or less useless if strong sulphuric acid and strong 
carbolic acid are as black to the chemical rays of light as nitrite 
of amyl and other fluids have beenshowntobe. Dr, Frankland 
makes no statement concerning this very important point. 
H. CHARLTON BasTIAN 
20, Queen Anne Street, W., Jan. 22 

The Tails of Comets, the Solar Corona, and the Aurora, 
considered as Electric Phenomena 
My attention has been called toa rudely worded attack by a 
certain Mr. Bedford, Phil. D., on Professor Reynolds, of Owens 
College. This is not the first time Mr. Bedford has offended in 
this way. Prof, Reynolds has not seen Mr, Bedford’s pamphlet, 
