446 
case, the task will be found to be impracticable ; but even when 
the overlap of the small disc is greater, the task can only be 
achieved by actually making new cusps out of the irradiation 
fringes. (A figure would make this explanation much simpler.) 
Prof. Newcomb says that he is decidedly of opinion that the 
irradiation of an extremely minute thread of light is not the same 
with that of a large disc. He does not seem to notice that if 
this is so, Venus just before, at, and just after internal contact, 
must be distorted. This even if—admitting the enlargement 
of the sun’s disc—he denies that the disc of Venus is reduced by 
irradiation. 
He fails also to observe that a peculiarity such as distortion, or 
the formation of a ligament, may escape the notice of inferior or 
not very attentive observers, and so all his negative observations 
be explained. It is no proof of superior skill in observation to 
see no signs of an illusory effect. Until we have observers who 
recognise no traces of irradiation when looking at the solar disc, 
we must believe that (as Mr. Stone has, I think, already asserted) 
the non-recognition of distortion or ligament formation is due to 
inattention, or want of observing skill. That this should be more 
common than close and careful scrutiny is not a very surprising 
circumstance, and proyes nothing. RicHarD A, PRocTror 

Oceanic Circulation 
In NaTuRE of August 17, I have just seen the report of the 
discussion on Dr. Carpenter’s paper on the above subject read at 
the late meeting of the British Association. 
Dr. Carpenter, explaining the movements on thermodynamic 
principles, states that he has ‘‘ found the gr7mm mobile of this 
circulation was not in equatorial heat but polar cold,” and 
explains that ‘‘ (1) As each surface-film cools and sinks, its place 
will be supplied, not from below, but by a surface influx of the 
water around ; and (2) the bottom stratum will flow away over 
the deepest parts of the basin, while, since the total heat of the 
liquid is kept up, there will be an upper stratum which will be 
drawn towards the cold area, to be precipitated to the bottom 
and repeat the action. Apply this principle to the great oceanic 
area that stretches between the equator and the poles, we should 
expect to find the upper stratum moving from the equator 
towards the poles, and its lower stratum from the poles towards 
the Equator. That such a movement really takes place is indi- 
cated, as it seems to me, by various facts.” 
It does mot appear, however, that Dr. Carpenter has well estab- 
lished his claim to the theories in question, while, in a pamphlet 
on the same subject, published in 1869 by Dr. Adolph Miihry of 
Gottingen, we find- such passages as the following :—‘* As the 
cause of the latitudinal circulation we have assumed the difference 
of temperature in the water between the equator and the pole.” 
He honestly gives Arago the credit of being, perhaps, the first 
to put forward this view in 1836; and after remarking (p. 11) 
that it might be considered doubtful whether it is the upper warm 
current from the equator or the under cold one from the pole 
that ought to be considered the primary, he says (p. 12) ‘‘ For 
us the primary ‘arm’ is the heavier, z.e., the colder polar stream, 
which, in obedience to gravitation, falls in a horizontal direction 
toward the lighter water of the hot zone; and the secondary 
‘arm’ is the returning antipolar. It moves to replace what 
flows away, andis, therefore, the compensation-arm.”’ 
Here, without following Dr. Mihry any further, we find the 
thermodynamic theory advanced by Dr. Carpenter, and his 
primum mobile as well; but by giving him credit for ignorance of 
Dr. Miihry’s work, we may excuse him for laying claim to what 
is there put forward, and accepting therefore the commendation 
of others as unknowing as himself. 

Ice Fleas 
DuRING a recent ramble upon the Morteratsch Glacier, I also 
observed a large number of the minute black creatures described 
by Prof. Frankland in NaTurRE, No. 100. My attention had 
been directed to them ten years ago by Lord Anson on the 
‘*snow-bones,” near the summit of the Aigischorn, They are 
only nominal ‘‘cousins” of the flea (Px/ex) of civilised life, and 
are not at all related to Dania, the ‘‘ water flea,” but are closely 
allied to the minute insects which are often seen on the surface of 
stagnant water, resembling grains of gunpowder, and skipping 
partly by help of their forked tail, folded under them so as to 
serve as a foot, hence their name Podura, or ‘‘skip-tail.” They 
have been named by Agassiz Desoria saltans. Their food, I 
conjectured with Prof, Frankland, consists of ‘‘red snow” and 
NATURE 


[ Oct. 5, 1871 

other microscopic alge. Not being myself within reach of a 
good library, I can only furnish your readers with a key to further 
information. C. A. JOHNS 
In Nature of 28th September, Prof. Frankland, in intro- 
ducing the ice flea to the readers of NATURE, uses the expression 
“if known at all,” and concludes by asking information about 
it. The glacier flea, Desoria glacialis, was noticed and described 
by Prof. Agassiz as far back as 1845, in his Ascent of the Wetter- 
horn on the 29th of July of that year. Not having Agassiz’s 
work at present beside me, I cannot refer to it, but these fleas 
are noticed in an extract translated from an account of the ascent, 
and published in Hoge’s Weekly Instructor for Dec. 1845, vol. ii. 
p. 221. Onthe Aar Glacier they:are described as being scattered 
over the ‘‘surface of the snow in millions,” elsewhere, ‘‘as 
being collected in masses under the stones on the ice.” 
The New Dynameter 
THE letter from the Rey. T. W. Webb in your last number 
is a very tantalising letter. He tells us, and we could not wish 
to have a better authority, that a new dynameter has been in- 
vented by the Rev. E. Berthon, but he does not tell us how it is 
constructed or where it can be obtained. 
I may take this opportunity of mentioning a makeshift dyna- 
meter which I have found to answer very well when extreme 
accuracy is not required. 
I have a pocket telescope fitted with a Cavallo micrometer, 
z.é., a slip of finely divided mother-of-pearl screwed to the dia- 
phragm next the eye-glass. Unscrewing the two last draws of 
this telescope the end of the second is applied to the eye-piece 
of the telescope of which the power is to be measured, and the 
first draw pushed in till the image of the object-glass comes sharp 
upon the mother-of-pearl. The diameter of the image is thus 
given in divisions on the mother-of-pearl, the value of which, in 
hundredths of an inch, has been previously ascertained. 
—_—— W. R. 
Notaris on Mosses 
WITH reference to the notice of De Notaris’ book on Mosses, 
Iam informed by Dr. Dickie that the genus Haébrodon was dis- 
covered in Great Britain several years ago by the late Mr. McKin- 
lay, of Glasgow, and that he had received from Mr. Wilson 
about two years ago from his district Covomitrium julianum. 
Dr. Dickie sends specimens of Hadbrodon Notarisii gathered at 
Killin by Dr. Stirton. M. J. BERKELEY 
*," In the review referred to, Prof. De Notaris was erro- 
neously described as of Geneva, instead of Genoa.—Ep, N, 
RC: 

“Newspaper Science” 
My attention has just been called to a letter from Mr. David 
Forbes which appears in NATURE, Sept. 21, under the head 
“Newspaper Science,” and in which that gentleman, writing from 
Boulogne, pathetically describes the emotions with which he read 
a recent “article” in the Glode on ‘* Krupp’s” Gun-manufactory 
at Essen. I need hardly say how deeply I deplore the shock 
which I have unwittingly been the agent of inflicting on your 
distinguished correspondent. It will be some small satisfaction 
if you will allow me to express the hope that the “ desired 
result ” of Mr. Forbes’s ‘‘ reluctant ” compliance with the advice 
of his “ medical man,” and most wise resolve “ to eschew every- 
thing scientific for the next few weeks at least, in order to recruit 
before the winter labours commenced,” may not be utterly de- 
feated by the perusal of ‘‘a specimen of English scientific 
opinion,” of which Iam unhappily the author. It would be a 
terrible reflection indeed, that a stupid error on my part had, 
perhaps, imperilled the accuracy and success of Mr. Forbes’s 
‘winter labours.” The blunder (or rather blunders) occurred 
as follows :—I, too, was ‘‘knocked up with work,” but being 
myself a ‘‘medical man” naturally only in part carried out my 
own prescription. I would, for the sake of Mr. Forbes, and 
the credit of ‘* English scientific opinion” in the estimation of 
his ‘‘ French acquaintance,” I had exercised a little more dis- 
cretion, However, unfortunately, I stumbled on the Krupp 
factory, and all forgetful of my dilapidated mental condition, 
wrote a note-paragraph (I never write ‘‘articles’’), which I 
vainly imagined might have been innocent and interesting. It is 
not always possible to compress even the manuscript necessary 
for a paragraph on toa single sheet of paper, and I grieve to 
say that after my paper had passed the editorial eye three words 
