FLAMES OF COMPOUNDS OF CARBON AND HYDROGEN. 425 
almost instantaneous appearance at very long intervals,—for it did occasionally 
appear for a moment,—satisfactorily proved it to be due merely to foreign matter 
which had accidentally entered the flame. 
From an examination, either of Table IV., or of Plate VIIL., fig. 1, it will be seen 
that certain of the lines in the carbohydrogen spectrum occupy nearly the same 
places in the scale of refrangibility with dark lines in the solar spectrum. These 
are the lines a, y, 0,, and g, which coincide more or less exactly with the lines D, 
6,, F,, and G. The first of these coincidences has been long known, having been 
discovered by FRAUNHOFER ;* and similar remarkable relations have been observed 
by Sir Davip Brewster to exist between certain lines in the spectrum produced 
by “deflagrating nitre,” and the corresponding lines of the solar spectrum.t+ 
From these singular coincidences occurring in so many different cases, the 
inference might be drawn, that all bright lines in the spectra of flames coincide 
with dark lines in the solar spectrum ; and the extremely close proximity of the 
lines y and 6,, 6, and F,, ¢ and G indicated in Table IV., might at first sight seem 
to confirm such an opinion. For it might be argued, that so close agreements in 
the ascertained deviations indicate absolute identity; the minute differences 
observed being attributed simply to errors in the observations. It will be seen, 
however, that the observed deviations of the lines 6, and y, differ by no less a 
quantity than 40”, which is quite beyond the sum of the probable limits of error 
in the observations for these lines, which I have ascertained to be only about 5”; 
and thus their coincidence is shown to be highly improbable. 
But any remaining doubt on the subject is completely removed, by the simul- 
taneous observations of the spectra of sun light and olefiant gas, given in Table V., 
where the micrometrical measurement of the interval between the lines 6 and 
differs only by 11” from that obtained by the theodolite observations. In fact, 
the bright line Y was seen when the spectra were viewed simultaneously, to coin- 
cide, not with the dark line b,, but with the clear space immediately beyond it. 
_ If we omit the line a, which, for reasons already fully stated, I do not regard as 
_ properly belonging to the carbohydrogen spectrum, not one of the other twelve 
lines which I have observed in that spectrum occurs near any conspicuous dark 
line of the solar spectrum, with the exception of the lines ry, 6, and z, which fall 
near b,, F, and G. Now, of these, y has been proved beyond doubt, not to coin- 
cide with ,, but with a bright space in its vicinity ; and from the simultaneous 
observation of the spectra of sun light and of olefiant gas, as well as from the 
_ results of the theodolite observations, I believe that the other bright lines of the 
carbohydrogen spectrum also coincide not with dark lines, but with bright spaces 
in the solar spectrum. 
* Scuumacuer’s Astronomische Abhandlungen, 1823, p. 29. See also Brewsrer’s Edinburgh 
Journal of Science, vol. viii, p. 7. M. Foucauur has lately verified this result with the double 
yellow line seen in the spectrum of the voltaic arc, between charcoal electrodes. See Dz La Rive’s 
Electricity, vol. ii., p. 322. 
+ Report of British Association, 1842, p. 15. 
