2 
ray of solar light be transmitted through a 
small slit aperture covering the object glass of 
a telescope, and received ou a prism for re- 
flection, and thence through another telescope 
to the eye, as in the instrument on the table, 
and the position of the principal dark lines 
noted, and their relative distances measured, 
so that a diagram may be drawn upon paper 
for reference, we shall possess a key, by 
which to detect differences that may exist in 
the spectra of other incandescent bodies. I 
may just observe that all solid or liqu d bodies 
give spectra containing no dark lines, but 
colored bands, as follows : — 
If we introduce into a flame of moderate 
luminosity, a small portion of any metal, or 
salt of a metd, we shall immediately see the 
bright colored bauds characteristic of such 
metal, and always occupying a definite posi- 
tion in the spectrum. The diagram on .he 
table shows, roughly, some of these 
phenomena. It is copied from one figured 
in Hoggendorf’s “ Annalen,” and published in 
tne “ London Edinburgh and Dublin Philoso- 
phical Magazine,” and some of the facts stated 
in this paper, are taken from the same source. 
If several substances be present at the same 
time, we see indications of all of them ; there is 
no ma king their presence as in most analyses 
by the ordinary chemical re-agents. 
By this means several new metals have, of 
late years, been discovered, — for instance the 
oik l ine metals Csedum, showing, in the spec- 
trum, bluish grey lines — and rubidium, show- 
ing two red lines, by Bunsen, in 1850. He 
evaporated some fifty tons of the Diirkheiui 
and Baden waters, to procure 2J0 grains of 
sold matter, which proved to be two new 
metals, bearing a proportion to the water of 
one to about six milli n parts. The latter 
metal, h is been shown, by Grundeau, to exist 
in the ashes of beet root, tobacco, coffee, grapes, 
&c., &c. These metals cannot by ordinary 
chemical tests, be distinguished from 
potassium, excepting that the double 
chlorides of Platinum afford very different, 
degress of solubility, while the carbonate of 
egesium is soluble in alcohol, thus affording a 
distinction from all other alkaline carbonates. 
A hot spring in the Wheal Clifford mine, in 
Cornwall, contains caesium, and is the only 
water in England in which it has been dis- 
covered. In 1861, Crookes discovered thal- 
lium, showing, unlike other substances 
a single line in the spectrum (light 
green) and that not coincident with any 
dark solar line. This metal is almo>t 
identical with lead in respect of color, specific 
gravity, softness, fusibility, specific heat, &\, 
and even in its poison symptoms, though 
Thallium is far more violent in its action. An 
ingot of this metal was exhibited lately (at 
General Sabine's conversazione) by Bell 
Brothers, weighing some 6000 grains. 
Professor Richter of Freiburg, in Saxony, 
discovered in a zinc ore in the Hartz, Indium, 
giving indigo, colored bands. 
Lithium, discovered in 1817 by Arfredsen, in 
the mineral petalite, was believed to be very rare, 
till Bunsen and Kirchoff, proved it, by spectral 
analysis, to be a most widely diffused metal, 
existing in almost all mineral waters, in tea, 
milk, human blood, and the ashes of some 
plants. This metal was detected, by Dr. Bence 
Jones, within a quarter of an hour of its exhi- 
fcdion, in the cornea, and iu the c irtitage of 
the hip joint. Sodium, showing one of the 
brightest., and most easily demonstrated lines 
in the spectrum, is nearly alwavs present, from 
its almost universal disiribuiion, being carried, 
no doubt by the wind, from the sea spray, to 
long distances. An instance of the very general 
disnibution of sodium, and of the delicacy of 
this means of detection, may be thus afforded. 
If a spectrum be obtained toieiably free from 
the sodium band, and a dusty book, or some 
such article, be shaken at a conside able distance 
from the lamp, the cliaract. ristic golden line, 
corresponding to the line D of Fraunho'er will 
instantly become visible. Dr. Fmnkiand has 
discovered this line when only a three billionth 
of a grain of sod am was present. 
I may just mention, in passing, that, minute 
as are the quantities appreciable by our present 
instruments of spectrum analysis, still more 
minute quantities are rendered evident by a me- 
thod adopted by Pi ofessor Tyndall, to ascertain 
the power of certain gaseous substances to 
absorb and radiate heat. In the in- 
strument u-ed, a quantity of boracic ether, 
equal to a pressure of only a thousand millionth 
of an atmosphere, is readily appreciable, when 
only three low tlis of a decree of heat centi- 
grade is imparted to it, deflecting the galvan- 
ometer needle 14 degrees. 
It mu-t n t be thought, however, that me- 
tallic bodies al me can be, by the above means, 
detected ; for though their spectra aie the most 
evident, as, for instance, in tobacco, wlieie we 
find the spectra of lime, lithium, potassiuiUj 
rubidium, and sodium, yet carbon, as shown in 
oxy, hydro, ni ro, and sulpho-caibor.s, gives a 
spectrum, the prevailing color of which is 
blue. Again, blood gives a spectrum contain- 
ing colored bands, not at all dependent upon 
the iron contained. 
Re fe ring to Professor Tyndall’s experi- 
ments, the field open for investiga ion in the 
matter of luminous and heat rays in combina- 
tion is very great, for when we consider that 
of the dazzling white light of platinum wire 
heated in the electric arc, only five per cent., 
ofcoalgas flame four percent., andof theelectrio 
light itself only ten per cent., are luminous 
rays, the rest being invisible rays of heat; and 
that these heat rays may be concentrated by 
lens upon any combu-tible body, and, in their 
turn, produce igni ion and light, and thus may 
be produced out of darkness, light which, ac- 
cording to Professor Tyndall, may equal that of 
