March 23, 1882] 
wie i At Be ee 
NATURE 
489 
that the concussion will raise a cloud of finely divided 
solid matter from the bottom of the tube along which 
the flame will be propagated and be driven out at the 
other end. A (see figure) is a wooden box 12 inches long, 
8 broad, and 6 deep, closed on all sides, with the excep- 
tion of a rectangular hole (34 X2# inches), into, which can 
be inserted a long narrow rectangular tube (B), also of 
wood, which may be 20 feet or more in length; the upper 
side (cc) of this tube is hinged, and along the bottom is 
strewed a thin layer of finely-divided dry coal-dust, or, 
what is better in the lecture-room, lycopodium powder. 
Into the wooden box, which in my apparatus has a 
cubic content of more than a gallon (5 litres) is 
placed about 1? pints (say 1 litre) of coal-gas; this 
can be most readily effected by pouring this amount of 
water into the box and displacing it over the water-trough 
by a current of the coal-gas. The opening is then 
closed by a sliding lid, and the gaseous contents are 
mixed by violently shaking the box for a minute or so. 
The end of the long tube (along which the powder or 
dust has been strewn, and the lid cc pushed down) is 
then inserted into the box, and the gaseous mixture is 
fired by thrusting a lighted taper through a small hole (¢) 
at the end just where the tube enters the box. The mix- 
ture of coal-gas and air explodes, and the flame rushes 
along the whole length of the tube with astonishing 
velocity, and is driven, often to a distance of six or seven 
feet, out at the other end, and is followed bya cloud of 
smoke. 
The experiment is unaccompanied by danger, and is 
so simple that it may be readily jperformed in a lecture- 
room. I showed it some time since to a number of 
colliers and others engaged in coal-mining, and it seemed 
to bring home to them far more forcibly than possibly 
any amount of mere description would have done, the 
real character of the phenomenon. T. E. THORPE 
THE PHOTOGRAPHIC SPECTRUM OF THE 
GREAT NEBULA IN ORION} 
AST evening (March 7) I succeeded in obtaining a 
photograph of the spectrum of the great nebula in 
Orion, extending from a little below F to beyond M in 
the ultra-violet. 
The same spectroscope and special arrangements, 
attached to the 18-inch Cassegrain telescope with metallic 
speculum belonging to the Royal Society, were employed 
which have been described in my paper on ‘‘ The Photo- 
graphic Spectra of Stars” (PAz/. Trans., 1880, p. 672). 
The exposure was limited by the coming up of clouds 
to forty-five minutes. The opening of the slit was made 
wider than during my work on the stars. 
The photographic plate shows a spectrum of bright 
lines, and also a narrower continuous spectrum which I 
think must be due to stellar light. The bright stars 
forming the trapezium in the “‘fish’s mouth’’ of the 
nebula were kept close to the side of the slit, so that the 
light from the adjacent brightest part of the nebula might 
enter the slit. 
Outside this stronger continuous spectrum I suspect an 
exceedingly faint trace of a continuous spectrum. In the 
diagram which accompanies this paper the spectrum of 
bright lines only is shown, which is certainly due to the 
light of the nebula. 
In my papers on the visible spectrum of the nebula in 
Orion, and other nebule (PAz7. 7rans., 1864, p. 437, and 
1868, p. 540; also Proc. Roy. Soc., 1865, p. 39, and 1872, 
p. 380), I found four bright lines. The brightest line, 
wave-length 5005, is coincident with the less refrangible 
component of the double line which is strongest in the 
spectrum of nitrogen. The second line has a wave-length 
of 4957 on Angstrém’s scale. The other two lines are 
* Paper read at the Royal Society, March 16, by William Huggins, 
1 OF OA Oy Os ON Op AS * _ = 
coincident with two lines of hydrogen, H or F, and Hy 
near G. 
In the photograph, these lines which had been observed 
in the visible spectrum are faint, but can be satisfactorily 
recognised and measured. In addition to these known 
lines, the photograph shows a relatively strong line in the 
ultra-violet, which has a wave-length 3730, or nearly so. 
The wide slit does not permit of quite the same accuracy 
of determination of position as was possible in the case 
of the spectra of stars. For the same reason, I cannot 
be certain whether this new line is really single, or is 
double or multiple. In the diagram the line is represented 
broad, to indicate its relative great intensity. 
This line appears to correspond to ¢ of the typical 
spectrum of white stars (Phz/. Trans., 1880, p. 677). In 
these stars the line is less strong than the hydrogen line 
near G; but in the nebula, it is much more intense than 
Hy. In the nebula, the hydrogen lines F and Hy are 
thin and defined, while in the white stars they are broad, 
and winged at the edges. The typical spectrum has been 
added, for the sake of comparison, to the diagram. 
I cannot say positively, that the lines of hydrogen 
between Hy and the line at 3730 are absent. If they 
exist in the spectrum of the nebula, they must be rela- 
tively very feeble. I suspect, indeed, some very faint 
lines at this part of the spectrum, and possibly beyond 
d 3730, but I am not certain of their presence. I hope, 
by longer exposures and with more sensitive plates, te 
obtain information on this and other points. It is, per- 
haps, not too much to hope, that the further knowledge 
of the spectrum of the nebulz afforded us by photo- 
graphy, may lead, by the help of terrestrial] experiments, 
to more definite information as to the state of things 
existing in those bodies. 
THE ACTION OF CARBONATE OF AMMONIA 
ON THE ROOTS OF CERTAIN PLANTS, AND 
ON CHLOROPHYLL BODIES* 
1. Roots. 
aL, ee observations which led to the first of these papers 
were originally made many years agoon Euphorbia 
Peplus, and have now been extended to other genera. A 
plant of &. peplus having been dug up and carefully 
washed, the smaller rootlets may be placed under the 
microscope without further preparation, the thicker roots 
may be examined by means of sections. If such roots 
are left, before being examined, in a solution of carbonate 
of ammonia (1 to 7 per 1000) for a short time (varying 
from a few minutes to several hours), they present a 
wonderfully changed appearance. The most striking 
alteration is that the surface of the root assumes a /ongz- 
tudinally striped appearance, due to longitudinal rows of 
darker brown cells, alternating with lighter coloured 
rows. The darker colour is seen under a high power to 
be due to the presence of innumerable rounded granules 
of a brown tint, which the lighter-coloured cells are with- 
out. Similar brown granules are deposited in cells scat- 
tered throughout the parenchyma, and markedly in the 
elongated endoderm cells surrounding the vascular 
bundle. 
The granules are apparently neither resinous nor fatty, 
for they are not removed by alcohol or ether ; they are, 
© Abstract by Mr. Francis Darwin of two papers by Mr. Charles Darwing 
read before the Linnean Society on March 16. 
