The New York herald. [volume] (New York [N.Y.]) 1840-1920, 1869-02-04
THE sPECTROsCOrE.
The Study Of Light and Its sources-IrshIy

The Study or Light and Its sources-IIighiy
Interesting Lecture by Professor Cook.
Professor Cook, OF Harvard University, Massachu-
setts lectured last evening at Seinway Hall before
large audience, on the Spectr0scope. In the abb
sence OF Judge DAILY Mr. Tillman, the Secretary OF
the American Institute introduced the learned lee
turcr who addressed himself at once to the subject
OF his DISCOURSE by saying that the color OF light de-
ponds to limited extent upon the nature of the
source from which it flows. by studying this color
Of light methodicaily we reach new chemical analy-
ses and have discovered new metallic compositions
on the globe; and we have also extended our in
quiries beyond the sphere OF this planet ana have
reached some knowledge OF the constitution OF the
heavenly bodies. The first principle to know is that
all bodies when sufficiently heated emit light; for
light is the necessary result OF high temperature.
The bar OF iron in the blacksmiths furnace,
the coal in the CRATES the gas which ilumines the
hail. Illustrations OF this principle In all these
the light has no peculiar color. but is white. The
source them from which light nows Is in every case
solid body and It is o universal truth that an in
candescent solid body always emits pure white
white light. 1t is not simple and not very
complex sensation. To Sir Isaac Newton we
means Of the prs Which separates the beams
OF white light into many colored rays. II
beam M Of Sunlight passes tnroush st IN door
rectilinear ltne on the opposite wall II glass lens
D6 tnterpOsed the image will still be perfect but II
prism, two distinct results. are reached. FIRST the
beam OF hight is bent to the left and the several col
ored rays spread out like the rays Of fan into
spectrum. If the dierent coors q light be recon-
bined they give pure white light again. Hence It
follows that pure white light is complex sensation,
composed OF dinerent simultaneous Impressions upon
the eye The Professor then produced the Instrument
invented to analyze light, the spectrOscOpe the me-
OF tube Is the slit TO admit the beam OF ght
the centre the prism which divides 1t and throws
aud then telescope is attached, the better to exam.
Inc the spectrum. There Is difference IN the angles
thrown BY the different coors OF the lights the red and
light hueS bent the least the violet and dark hueS
the most What was said Of lncandescent solid bodies
is true also OF liquids, which can be heated become
incandescent, Ike molten metal. 1t follows by
analogy that when we see pure white light It
emanates from luminous solid or liquid body. This
Is universally true on earth, and we may assume it
to be law OF nature throughout the universe The
light OF the sun and OF the liked stars Is pure white
light, and therefore they must be solid or liquid
globes and cannot be gases or vapOiS Tor the light
OF the later is far less intense at the same tempera
ture and there Is great difference between different
gases aud vap0rs. The rule has been established
that the denser the source the more brilliant
the light Hence the dense metallic vapors
The Professor explained an apparent contradiction
To this theory IN the burning OF coal gas; but 1t
not the gas which burns, but minute particles Of
showed this by experimenting with two Bunsen
burners. The Professor then burned common salt
compound OF sodium and chiorlne-by which the
red color OF o sheet OF paper was turned to pale
white. The source Of light here was sodium yapor.
He then burned lithIum in another flame, and pro-
duced red light, the source Of which was lithium
vapOr. He then experimental with sulphur and
ntre used In irew orks, producing pale yellow, red
and green Light, the sources being either sodium, lithi
UNI, bOerum or stranti0n. by passing q. current Of
electricity the light made to shine still more bril-
antly. Knowing all this. we can, by means Of the
speciroscope, analyze the light and determine tho
nature Of Its source. New metallic elements have
been discovered by this means sources Of light
rubidium, sysunl, thaun and lndium. And this
has also led to q knowledge OF the cOnsti-
tuition OF the heavenly bodies. The sun and the
fixed stars have been found TO be solid or liquid
globes the light from which It has been determined
passes through sodium atmosphere Immediately
surrounding them. The nebul8 aud their nature IS
gaseous or vap0rous bodies, determined by the
analysis OF their light in the spectrOscOpe were at
length spoken or The absorbing qualities OF light
were detailed. The solar spectrum was explained
and the manner in which to determine the precise
quality Of the source OF light given In very detailed
and interesting manner and that the character OF
the metallic composition OF the sun and his atmo-
sphere containing calcium magnesium, nickel,
boerium, zinc aud others, but neither gold silver,
antlnony nor strantlon and several others had been
thus liked. The lecturer closed with numerous beau
tu experiments some OF which did not succeed 30
well as anticipated on account OF some derange-
ment In the apparatus erected on high platform IN
rha cautra Of "a IA