May 25, 1871] 
NATURE 
m1 

1847. The truth is that the numerical calculations neces- 
sarily entailed for the reduction and the discussion of the 
observations, occasioned an amount of labour inconceivable 
to those who are strangers to the requirements of exact 
astronomical research, and upon all this labour he per- 
sonally entered. To explain what he required, to such a 
mind as his, would have been more troublesome and dis- 
tasteful than to do it himself. As he had done before, so 
he did now, and so he did again and again while con- 
sciousness was accorded to him, he laboured with his 
own hands. But the book itself, ultimately published by 
the noble and well-judged munificence of the Duke of 
Northumberland, is by no means a monumeni of industry 
alone ; itabounds, inalmost every page ofits many notes and 
appendices, with original discoveries, suggestions, specu- 
lations, grand and comprehensive conceptions of the dis- 
tribution of the celestial universe, which will require many 
a long year to elapse before their significance is ex- 
hausted. We may take as an illustration the first 
instance that occurs to us, ina suggestion, made in a note 
of Herschel’s which might, and fora long time did, escape 
the reader’s notice. He suggests that the main difficulty 
which occurs in the observation of the sun’s photosphere 
might be removed by viewing its light when reflected from 
the first surface of a glass prism, which, at the same time, 
permits the greater part of the heat to escape away from 
the observer’s eye. This simple contrivance, thus rapidly 
suggested by the way, lies at the bottom of more than 
one discovery which has since been made relative to the 
constitution of the solar photosphere ; but similar instances 
abound. 
It is hardly necessary to refer to the multiplied and 
well-earned honours which awaited John Herschel on his 
return from the Cape of Good Hope. He might have 
been elected to the Presidency of the Royal Society, but 
he retired in favour of the Duke of Sussex ; and shortly 
afterwards, not alone for his own sake but for the sub- 
stantial recognition of an illustrious name among the 
worthy families of his country, he was made a Baronet of 
the United Kingdom. Like his great predecessor Sir 
Isaac Newton, he might have been returned as the repre- 
sentative in Parliament of that noble University where 
his intellect was nurtured and grew, until it became its 
brightest and fondest ornament ; this honour he declined. 
Subsequently he was appointed, again like Newton, to the 
lucrative post of the Mastership of the Mint; but his 
gentle and unsophisticated nature was ill adapted to cope 
with the occasional unrealities and difficulties of an official 
life ; it affected his health, and he retired after a tenure 
of a few years. 
Our space forbids us, in this place, to enter upon the 
more recent portions of this illustrious man’s public and 
scientific career ; indeed it cannot fail to be sufficiently 
known to the great majority of our readers. His true 
place in the philosophy, and among the great lights of 
his age, cannot be accurately fixed, until his own genera- 
tion shall have entirely passed away ; for the feelings, the 
partialities, the prejudices of contemporaneous life, una- 
voidably warp and incapacitate the judgment, just as too 
close a proximity to a mass or a multitude is unfavourable 
to a correct appreciation ofits true proportions. Some time 
after the death of Laplace, the writer of this notice, while 
travelling on the Continent in company with the celebrated 
French savazz Biot, ventured to put to him the question, 
not altogether a wise one—“‘ And whom of all the philoso- 
phers of Europe do you regard as the most worthy suc- 
cessor of Laplace?” Probably no man was better able 
than Biot to form a correct conclusion, and the reply was 
more judicious than the question. It was this,—“ If I 
did not love him so much, I should unhesitatingly say, 
John Herschel.” It is from a loving reverence for the 
memory of a great philosopher and a good man that we 
now venture to say no more. 
Out of the large number of mourning friends who last 

week in Westminster Abbey gazed with reverential regret 
at the sorrowful procession which followed the mortal re- 
mains of John Herschel, till they were deposited among 
the best loved and most highly honoured of the worthies of 
past time, not a few must have recalled to their memories 
how in their scientific difficulties, or anticipations, or suc- 
cesses, they had betaken themselves to the aged philo- 
sopher of Collingwood, and had never failed to meet with 
the ready aid of a kindly and courteous sympathy. 

SIR F. HERSCHEL ON OCEAN CURRENTS 
WE are permitted to publish the following letter 
(probably one of the last written by Sir John 
Herschel on scientific subjects) which was addressed by 
him to Dr. Carpenter, with reference to his paper in the 
Proceedings of the Royal Geographical Society, ‘‘ On the 
Gibraltar Current, the Gulf Stream, and the General 
Oceanic Circulation,” a copy of which had been forwarded 
to him by Dr. Carpenter on its publication, with a request 
that he would reconsider the opinions he had formerly 
expressed as to the inadequacy of differences of tempera- 
ture and specific gravity to produce great movements of 
ocean water :— 
“Collingwood, April 19, 1871 
“My Dear Srr,—Many thanks for your paper on the 
Gibraltar Current and Gulf Stream. 
“ Assuredly, after well considering all you say, as well as the 
common sense of the matter, and the experience of our hot- 
water circulation-pipes in our green-houses, &c., there is no 
refusing to admit that an oceanic circulation of some sort must 
arise from mere heat, cold, and evaporation as vere causz, and 
you have brought forward with singular emphasis the more 
powerful action of the polar cold, or rather the more intense 
action, as its maximum effect is limited to a much smaller area 
than that of the maximum of equatorial heat. 
“ The action of the trade and counter-trade winds in like manner 
cannot be ignored ; and henceforwards the question of ocean- 
currents will have to be studied under a two-fold point of view. 
The wind-currents, however, are of easier investigation. All the 
causes lie on the surface ; none of the agencies escape our notice ; 
the configuration of coasts, which mainly determines their direc- 
tion, is patent to sight. It is otherwise with the other class of 
movements. They take place in the depths of the ocean; and 
their movements and directions and channels of concentration are 
limited by the configuration of the sea-bottom, which has to be 
studied over its whole extent by the very imperfect method of 
sounding. 
“Tam glad you succeeded in getting specimens of Mediterranean 
water near the place of the presumed ‘salt spring of* Smyth 
and Wollaston, making it clear that the whole affair must have 
arisen from some accidental substitution of one bottle for another, 
or from evaporation. I never put any hearty faith in it. 
“*So, after all, there zs an under-current setting outwards in 
the Straits of Gibraltar. 
“Repeating my thanks for this interesting memoir, believe me, 
Dear Sir, 
** Yours very truly, 
“cj. F. W. HEeRscHeL 
““Dr. W. B. Carpenter.” 
We congratulate Dr, Carpenter on having obtained 
from so eminent an authority, as one of the last acts of 
his honoured life, this cordial and well-considered accept- 
ance of the doctrine he had previously opposed ; and this 
distinct recognition of the new aspect in which Dr. Car- 
penter’s own observations and reasonings had placed it. 
The success of his appeal shows that he did not under- 
rate the noble candour of the great philosopher, to whom, 
more than thirty years previously, he had dedicated his 
first scientific treatise,as an expression of his gratitude 
for the moral and intellectual benefit he had derived from 
the “ Preliminary Discourse on the Study of Natural 
Philosophy.” We shall return to this subject next week. 
