314 
To make the exposure, the plate was drawn up until the 
projecting pin, D, could be caught on the lever, K, which 
would then retain it. On depressing the outer end of this 
lever, however, with the finger, the hold on the pin was 
disengaged, and the plate flashed across the axis of the 
tube, allowing light to traverse the narrow slit as it flew 
past. The plate was then arrested on the end of the 
second lever, G. When an exposure of some seconds was 
required, as during the totality, a plate having a round 
orifice exposing the entire field of the eye-piece was 
substituted for the one with the narrow slit, and was so 
arranged that, when caught by the upper lever, it covered 
the lens, but when fallen to the second lever, exposed it 
entirely; when, however, this lever was in turn touched, 
the plate descended again far enough once more to close 
the lens. By touching these two levers in succession, it 
was then possible to make a “time exposure” with great 
nicety and accuracy, as proved by actual experience during 
the eclipse. 
To secure a chronographic record of each exposure, a 
binding screw was provided to make one connection with 
the general mass of the face-plate including lever K, and 
another at L, to carry on the circuit when the downward 
motion of the lever brought the spring at its side in 
contact with the point projecting from L. In raising the 
lever for a new exposure, the spring at its side was pressed 
[Zhe Editor does not hol himself responsible for opinions expressed 
by his Correspondents. No notice is taken of anonyaous 
communications. | 
Kant’s View of Space 
THE following paragraphs, I believe, faithfully render sundry 
passages of Kant’s writings :-— 
“Objects are given to us by means of sense (Sinnlichkeit), 
which is the sole source of intuitions (Anschauungen) ; but they 
are thought by the understanding, from which arise conceptions 
(Begriffe).” (‘* Kritik,” p. 55. Hartenstein’s Edition. ) 
““The understanding is the faculty of thought. Thought is 
knowledge by means of conception.” (did. p. 93.) 
“*The original consciousness of space is an intuition @ /rio77, 
and not a conception (Begriff).” (/ézd. p. 60.) 
“«Space is nothing else than the form of all the phenomena of 
the external senses ; that is, it is the subjective condition of 
sense, under which alone external intuition is possible for us.” 
(/bid. p. 61.) 
‘*Our nature is such, that intuition can never be otherwise 
than sensual (Sinnlich); that is, it only contains the modes in 
which we are affected by objects. On the other hand, the power 
of thinking the object of sensual intuition, is the understanding. 
Neither of these faculties is superior to the other. Without 
sense, no object would be given us, and without understanding 
none would be thought. Thoughts without contents are empty, 
intuitions without conceptions (Begriffe) are blind.” (Zérd. p. 82.) 
“Time and space are ‘mere forms of sense’ ” (Formen unserer 
Sinnlichkeit, ‘* Prolegomena,”’ p. 33) and ‘‘ mere forms of intui- 
tion.” (*‘ Kritik,” p. 76.) 
With these passages before one, there can be no doubt that 
that thorough and acute student of Kant, Dr. Ingleby, was 
perfectly right when he said that Kant would haye repudiated 
the affirmation that ‘‘space is a form of thought.” For in these 
sentences, and in many others which might be cited, Kant 
expressly lays down the doctrine that thought is the work of the 
understanding, intuition of the sense ; and that space, like time, 
is an intuitions The only ‘‘ forms of thought” in Kant’s sense, 
are the categories. T. H. HUXxLry 
January 14 
I po not believe Professor Sylvester has been betrayed, as 
Mr. G. H. Lewes asserts, into any misconception of this matter 
by me. 
When Kant, at the outset, says, ‘* Alles Denken aber muss 
sich, es sei geradezu oder im Umschweife, vermittelst gewisser 
Merkmale, zuletzt auf Anschauungen,..beziehen,” it would take 
the veriest dunderhead not to see that all forms of intuition must be, 
ndirectly at least, forms of thought, I neyer dreamed of disputing 
WA TORE 
[ Fan. 20, 1870 
so obvious a position, But I object to the phrase ‘‘ forms of 
thought,” as designating Space and Time, on the ground of pre- 
cision. They are feculiar/y forms of general Sense, and not 
forms of Thought as Zhought. IWant, I believe, eschewed the 
phrase in that sense, and, for all I see, might for the same reason 
have disclaimed it. 
ford, Jan, 14 C, M. INGLEBY 
Ir is not my habit ““when objections are made to what I have 
written, silently to correct my error or silently disregard the 
criticism.” If the objections are well founded, [ think it due to 
the cause of truth to make a frank confession of error, and in 
the opposite case to reply to the objections. 
With reference, then, to Mr. Lewes’s strictures in NATURKE’S 
last number, I beg to say that Dr. Ingleby has ** betrayed” me 
into no error. If I have fallen into error, it is with my eyes open, 
and after satisfying myself by study of Kant, that to speak of 
Space and Time, whether as forms of understanding, or as forms 
of thought, is an unauthorised and misleading mode of expression. 
Space and Time are forms of sensitivity or intuition, The 
categories of Kant (so essentially in this point differing from those 
of Aristotle) do not contain Space and Time among them, and 
are properly called forms of understanding or thought. 
To the existence of thought the operation of the understanding 
is a necessary preliminary. 
Sensibility and intuition are antecedent to any such operation. 
Can Mr. Lewes point to any passage in Kant where Space and 
Time are designated forms of thought? I shall indeed be sur- 
prised if he can do so—as much surprised as if Mr. Todhunter or 
Mr. Routh, in their Mechanical Treatises, were to treat exergy and 
force as convertible terms. To such a misuse of the word energy 
it would be little to the point to urge that force without energy is 
a mere potential tendency. It is just as little to the point in the 
matter at issue, for Mr. Lewes to inform the readers of NATURE 
that zz¢durtion without thought 1s mere sensuous inipression. 
Dr. Ingleby has rendered, in my opinion, a very great service - 
| to the English reading public, by drawing attention to so serious 
and prevalent an error as that of confounding the categories (the © 
proper forms of thought as ¢howght) with Space and Time, the 
forms of intuition, the Sentinels, so to say, who keep watch and 
ward outside the gates of the Understanding. 
Atheneum Club, Jan. 15 J- J. SYLVESTER 
Correlation of Colour and Music 
SOME twenty-six or twenty-seven years ago, in a lecture 
on Light at the London Institution, I suggested an analogy 
between the octaves of Sound and Light ; not then knowing the 
view of Sir J. Herschel to which Dr. Pereira subsequently 
called my attention. : 
I endeavoured to support the hypothesis of three primary 
colours by supposing the intermediate colours to arise from the 
blending of the primary. Thus orange would result from the 
blending of red and yellow, green from yellow and blue, and 
violet from the secondary red impinging on the blue or indigo. 
This seemed to me a less arbitrary explanation than that of Sir 
D. Brewster of a superposition (in degrees of intensity chosen to suit 
the hypothesis) of all the primary colours throughout the whole 
spectrum. Spectrum analysis has now much changed our views 
on this subject. 
The interesting article in your number for January 13, by Mr. 
Barrett, has recalled my attention to the matter, and induces me 
to ask whether he, or any of your contributors, can explain a 
phenomenon which I have very often observed, as have doubt- 
less others, but which I have never seen noticed in any work on 
Light. 
It is this. When a very brilliant solar-rainbow is seen, there 
is plainly visible within, and forming a continuous spectrum 
with the main rainbow, a repetition, but in much narrower bands, 
of the rainbow : the same seven colours in the same order ; and 
within this again, I have, on certain occasions, detected a third. 
Are these repetitions of the spectrum as suggested by Sir J. 
Herschel ? If so, we should have two, three, and more reds, and 
so of the other colours, in which light, producing the impression 
of the same colour on the retina, would have different wave- 
lengths, say, in the ratios of one, two, four, &c.; or is the 
phenomenon due to some other cause? W. K. GROVE 
January 15 
J VENrUuR« to call attention to a curious point in connection 
with the very interesting note by Mr. W. F. Barrett on the - 
“Correlation of Colour and Music,” which appeared in yester- 
