The British Press; or, Morning Literary Advertiser.
London, England, 1824-09-27 00:00:00

LITEII.4TURE.

THE EDINDURCH J

RN AL OF SCIENCE.

•LACK wOrm_Enmovanw.
We have just received tu.• (Maher number of ilia work,
and are decidedly et' opinion that it does not belie the pio-
raise of excellence which is predecessor led us to expect.
In the list of contributions, we observe names which stand
high in scientific character, v;r..:--Si'enlloch, Hooker,
Knox, Sir Thuntas Brisbane, Dr. Francis Hamilton, and
many others, who cannot fail to make such a work va-
luable. It is difficult, in a work purely scientific, to find
much to interest the mitt-al reader; but we think the
following may not hi: unacceptable to many of our
readers:—
- -

ON • NCTIIOD 07 lEADI1;O TUE INSCtIPTIONS ON
COIK• •ND PIEDAI • IN TIIZ DARK, WITH IIMAIIII4

OR TILL RADIATION Or DETALLIC RURTACLII.
" Among the numerous experiments of a striking and'
popular nature. with which scion: astonishes, and soma.-
times even strikes terror into the ignorant. there is perhaps
none more calculated to produce this effect than the one
which forms the subject of the roman article, while it
possesses at the same time the higher advantage of present-
tht to us some scientific facts, which we believe have not
hitherto hen observed.
" It has long been khown that Nock surfaces radiate heat,
or throw it off more copiously than while surfaces ; and
that the saute difference takes place between rough and
pi'i.6 of surfaces • those which are rough prcalncing the
fame effect u those which are black ; but in leo far as we
learn, uo experiment has been made to prove, that the
same results take place with radiant light; that is, that
when bodies are bested to such a degree as to radiate
light, those which have Glide or re ngh surfaces dierherge
the light wore copiously than those which are white or
"'!'his result respecting radiant light might no doubt
leave been inferred from the experiments on the radiation
of heat, if these two sot:stances had been previously found
to comport themselves in a similar manner when thrown on'
by Lodits, or reflected from their surfaces. Lint this has
never been established; and therefere such an inference
would have been premature in the present state of our
kills ledge. if we contide in experiments already made,
indeed, we should be ireaposeil to conclude, that light and
heat du not follow the same laws, at least in their reflec-
tion from holies. Brass, for example, is said by Mr.
Leslie to have a reflective power for heat of 100-., while
silver has only a rilective power of 00.2; but we know
for certain, that silver reflects light much more copiously
than brass. Notwithstanding this apparent discrepancy,
we would rather question the accuracy of the experimeet,
than the truth of a law which has long been considered as
general.
" Duriug the experiments on the revival of the inscrip-
tion on coins by unequal oxidation, which we have described
in our last Number, we had occasion to expose to a high
degree of heat a coin, on which the inscription had been
rendered black by oxidation. Upon taking the coin, while
in a state of bright red heat, into a dark roam, we were
stir:a-bled to u`aierve that the letters of the inscription were
inure luminous than the rest of the coin, in consequence of
their oxidated surface radiating the red light more copiously
than the other parts. Though the effect was not in this
case sufficiently sulking to enable me to read the inscrip-
Von, yet it occurred to me, that if by the action of au acid,
or any mechanical means, the general surface of the coin
should be made rowel, or have its polish removed, while
the raised points which cunatituteil the inscription and the
figure were polished, an effect opposite to that in the pre-
ceding experiment should be produced. I accordingly took
a French shilling of Louis XV. and having roughened the
depressed parts of the surface, and heightened the polish
of the inscription, Ac. I placed it upon a red hot mass of
iron, and removed it into a dark roost. Wiwi) the shilling
began to radiate light, the inscription " Ilene/Odom Si!
Numen Del loppettrcd in obscure lett rs, while the ground
em which thov stool shone with a brilliant light. By
inlishing the elepressod pelts of the surface, and roughen-
ing the letters. I obtained, as might have been expected,
the opposite effect, the inscription being now legible, from
its throwing off mare light than the surrounding surface.
" In order to perform this cloy timent with most success.
it is desirable to conceal from the observer's eye the mass of
red hot iron on which the coin is placed, both for the pur-
pose of rendering the eye fitter for observing the effect, and
of removing all doubt that the inscription is really read in
the dark ; that ix, without the light of any other body
either direct or reflected upon it.
. " The most striking form in which this experiment can
he exibited, is to use a coin from which the inscripeon
has tither been wholly obliterated, or obliterated in such a
degree as to be no longer legible. NVIe n such a coin is
Wel upon the nil hot iron, the letters and figure become
oxidated, as formerly described; and the black or brown
filen of oxide which is found upon them radiating more
powerfully than the rest of the coin, the letters will shine
more brilliantly than the other parts, and may be read to,
the great surprise of the observer, who hadexamined the
blank surface of the coin before it hail b. en placed upon tl e
Ilissurprise will nut heiliminisbeel, when he ofeserves
that the letters which he saw more luminous than the rest
are now covered with the black film of oxide.

"As the different radiatirg powers of parts of the same
surface, can neither be aeen by the eye nor indicated by any
instrument, when the general temperature is below that of
red heat, the principle of the preceding experiment may be
employed to di termine the relative powers of radiation
pessessizd by ditrerent metals. Although the radiating
powers, for example, of gold, silver, copper, and tin plate,
are, according to the experinwnts of :Mr. Leslie, exactly
the same, yet we are persuades' that the preceding int this'
will affird ocular deinonstratit n of the incorrectness of this
result, when these bodies arc stilnnitteil to the experiment
u al t the same ci rcinnstances of to ogrii t tide, thickutu, and
polish, in so far as this can be dom.. This opinion is not
'melanin! on an conjecture, but is founded on very
unequivocal exp,:riin-nts on the ?effective powers of these
tunas for light, which differ in a very considerable th_tree,
mid which in general have • fixed relation to their radiating
pl;werv.

" In the ease 31 pure 'diver, which has been ground and
pilishuit, the elective power exe.ll:s that of all other
ut.:tals that we have tried • and catinot suppose it a
matter of doubt. that the r;sdiating power of silver is much
lee than that of gold or copper, and inferior to that of
tin plate.
Alanne the other laws of radiation, it has ben an-
nounced that die thinnest cost of a metallic body produces
se great an effect as the thickest. This law is by no means
improltahl:•, but it requhes to tic continued by nicer me
tbals titan those by which it was ataineit ; and we are
not aware that a more correct ulw can be found than the
Fece.es which has been tnilt:ionetl.

6t..... -
In the experiment with the coin, where the different
puts raliate different degrees of liglit, the effect does not
skew bself tiil the heat has rism to a particular deice of
iatensity. As this point may vary with differ:eta metals,
El with the different states or condi:ions of the two ra-
dian*: surfaces, might it not he employed with success for
tremetrical purposes, schen the temperature to be 'ilea-
ttirrd elz:reda that of red Lest? A serus of well-devised
aud nicely-conducted experiments oa this subject, would
lead to very interesting resteta, even if they should not
kirlf4 data for the construction of a new pytoteeter.
" There are many other useful purposes in the arts. as
w;11 as in the sciences, to which we cot:::..ive the preceding
',sults may Le applicable ; but as the discussion of them
you'd not be approptiate in a popular article like the
p-,.!.nt, we shall rteilltie the subject on some tante oc-

The ease of an individual recently charged at the Man-
OA
-house with an huh wit assault on two females, has
he, copied into the Owt,/ia Freeman's Journal, with the
e. " Character of the English people," in large letters.
1 e g:n ral remarks made by the Lord Mayor on the case
▪ to, sr. em to have obtained fur the " English people"
tte distinct:ln. It is, however, about as ridicu-
lous as the ate:aril notisoiso lately put into the mouth of
(-muse:* 0 Connell, who is represented to have said that
1111.• Parliamentary Returns prove that nineteen out of every
w ttty 1112Trilli Euglishwunten live separate from ilk tr
iliAbstAls —We cannot help being amused at finding an
'lame "of the rank," (we are quoting an Irish speech)
0 of kir. ()Connell," cajoled into the belief that such Par-
anieutary paper, as he describ:s ever existed.