Feb. 10, 1870] 
NAT ORE 
385 
differ not inconsiderably from those which belong to the musical 
scale and he is obliged, afterall, to place blue and indigo together, 
taking their ‘‘mean rates” as corresponding with G. I do not 
know how far Newton’s measurements are correct ; but I find 
that Professor Zannotti, of Naples, gives for the diameters of the 
rings from red to red the cube-roots of the numbers I, $, %, is i 
1. The intervals between these, taken successively, are 
2 38, 0°, & 4, 4%, 2; that is—major-tone, semi-tone, minor- 
tone, major-tone, minor-tone, 4-tone, major-tone. Calling the 
major-tone J/, the minor tone wz, and the semi-tone x, for the 
sake of brevity. I will give the five different forms of which the 
musical scale is capable—expressed by the succession of intervals 
—and show that the above series of intervals is one of them :— 
yy Cape ADC; D 
(1) m x M m M Be M, or 
2 Sintono. 
(2) M x m M m x M, or 
Newton’s scale of colours. 
(3) M x M m M x m 
(4) m x M M m x M 
(5) M x m M M x m 
Varieties depending upon the permutation of the quantities M, 
m,and x. The Ist contains the imperfect fifth,DA; the 2nd 
two such fifths, EB and FC; the 3rd GD; the ath A,E,; and the 
5th the imperfect fifth, C,G,—all of course with their corre- 
sponding augmented fourths. 
Thus, Newton’s scale of colour is one of a series of five scales 
of sound, all requiring modification by a coma of one, or at 
the most two-fifths; but all are found of perfect major and 
minor tones and major semitones. If the correlation between 
colour and sound exists, I think it will be found here. If this 
be admitted, the colours and notes corresponding are as 
follows :— 
1, 1, im Ve, Ay. 20 xe 
Red, Orange, Yellow, Green, Blue, Indigo, Violet, Red ; 
or better according to the figure— 
Thus the series of colours corresponds with the Gregorian 
Scale of the fist mode and not with the modern scale of C. I 
may remark, by the way, that the ancient Greek Plain chant is 
said sometimes to have a notation in which the notes are distin- 
guished by different colours. It would he interesting to know 
whether such a notation has any scientific foundation. 
In conclusion, I would say, that Newton’s rings give a far 
more clear division of the colours that we get in the spectrum 
and the distinction between blue and indigo is too well defined 
to warrant them to be treated as Mr. Barrett has done. No 
doubt the neighbourhood of indigo is a difficult one and to make 
the correlation with sound complete, this colour itself ought to 
be divided into two ; indigo-blue and indigo-violet corresponding 
to the notes B9 and Bf, both of which are required to obtain the 
fourths and fifths all perfect. Allow me to inquire if there be 
any marked line in the red, dividing it into two reds separated by 
the interval $4? I ask this question because the Sintono Scale 
(1) requires two D’s differing by this interval, to complete its 
intervals of fourths and fifths. Also, would the correction of the 
fifths, &c., in the other four scales given above, by the introduc- 
tion of one or two new notes, be such that these notes can be 
made to correspond to marked divisions in the spectrum or to 
like divisions in the series of colours determined by Newton’s 
method ? W. S. OKELY 
THE supposed analogy between the spectrum and the musical 
scale is not strictly accurate, because in the former the colours 
blend into one another imperceptibly, while the notes of the 
latter are separated by distinct intervals. 
Yet it is precisely on this blending of the colours that the 
pleasing effect of the spectrum depends. If we place red, 
orange, yellow, &c., in their order, in immediate juxtaposition, 
as distinctly defined bands, we obtain precisely that arrangement 
which is admittedly distasteful. 
The chromatic scale, as its name implies, approaches more 
nearly to the spectrum than does the diatonic; but the spectrum 
would be still better represented by the sliding tones produced by 
running the finger up the sounding string of a violin. 
But leaving this objection, which may be thought too critical, 
I would remark, that the analogy which Mr. Barrett points to is 
rather one of melody than of harmony. 
In the case of a musical concord. the two notes fall simulta- 
neously on the ear and are perceived as one compound sound, 
the effect of which is very different from that produced by 
sounding the notes in succession, however rapid ; yet this last 
is what rather seems to correspond to the sensation produced by 
two colours placed in juxtaposition, the eye passing rapidly from 
the one to the other. To obtain the optical analogue of a 
musical concord, the colours ought to be received simultaneously 
on the retina—in other words, should be blended. Could not 
this be accomplished by producing two distinct spectra by means 
of two prisms and causing the so-called harmonious colours in 
either to overlap one another on the screen? Blending thus, for 
example, those rays of the two spectra whose vibrations are to 
one another in the ratio of 100 to 75, their resultant (a purple of 
some sort, I suppose) would give us the true analogue of the 
fifth in music. 
Similar experiments, I am aware, have been made by causing 
patches of colours to rotate upon a discso rapidly that they are in 
effect blended upon the retina ; but some modification of the 
method above suggested would seem to have the immense ad- 
vantage of enabling the experimenter to combine colours whose 
wave-lengths would be in any desired ratio. 
I should be curious to know whether the result of such an 
experiment would be that the compound tint produced by the 
two rays would be more or less agreeable, the more or less nearly 
its component parts were in the exact musical ratio; also 
whether, when the two colours were slightly ‘‘out of tune,” we 
should have the phenomena of ‘‘interference” presenting them- 
selves analogous to the ‘‘ beats ” in music. 
A curious speculation here suggests itself. It is well known 
that what are called complementary colours—red and green, for 
instance—nroduce, if combined in due proportions, white. 
Proceeding by the above method, then, should we find that 
the particular tints of red and green necessary to produce white, 
are those whose ratio is exactly that of the musical fourth? 
Tf so, white is as much entitled to a place in our catalogue of 
colours as purple or any other harmonised compound. 
If white is not the optical representative of the musical fourth, 
where shall we look for its analogue in the latter science? Can 
any of your readers suggest a method of producing a white 
sound? ‘*White,” we know, is the resultant of the blending of 
the whole rays of the spectrum—z. e., of the same part of the 
retina simultaneously receiving rays whose wave-lengths pass 
imperceptibly through every conceivable shade of difference. 
If it were possible for a violinist to slide his finger up the 
string of his instrument in such a way that, instead of producing 
a sound varying in pitch, every part of the string passed over 
should continue to sound simultaneously with every other part ; 
or, if we can suppose some millions of violinists each sounding a 
note inappreciably higher than his neighbour, but comprehending 
among them every conceivable shade cf pitch within the octave, 
we might possibly obtain the purest and most ztherial of tones, 
a ‘*White Sound!” 
Edinburgh, Jan. 24 
Francis DEAS 
Government Aid to Science 
WILL you allow me, with the utmost respect, to remind your 
able correspondent, that every zndividual in the state pays taxes 
for ignorance and inefhciency; while so interwoven are the 
interests of man with man—so often does inquiry after the most 
abstract principles lead to valuable practical results, that it is 
impossible to predict in which department of Science discoveries 
may be made that shall materially lighten these unsatisfactory 
imposts, Hence the field of research should be open to all and 
