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On the pbotoroeter* A coating of brown or white silk also inva*
riably gave a much less effect than Indian ink, or a surfiica <^
Uack glass.

* These results seem to me decisive against the hypothesis of a
superposition of two spectra^ one of luminous, atid the other of
calorific rays.

< (62.) It Is obvious (hat the greater heating power disfdaj^ed
by the rays towards the red end of the spectrum, may b« owiiig^
td either of the following causes, or to both jointly.

* LA greater intrinsic power of communicating heat.

1 2. A greater number of particles brought jnto action, of

absorbed.

- And this last Cause may depend either upon the peculiar state

ef division to which the rays may be reduced, or upon a greater

pdwer of absorption in the surface for these than for other

coloured raysy or here aigain both causes.may co*operatcf^

With respect to the state of diffusion of the ravs, it is obvious
that the red ra^s are inot^ concentrated than the yellow, and
these mord than the blue, 9le. ; so that from this cause alone we
might expect a greater heating effect ; a greater number of par»
ticles actmg in the same space.

'• With respect to a possible increase of absorptive power iu
respect to the gre^^ter approach to the character of the extreme
red light; I am not aware that we at present possess any r^ulla
whieh can assist such an inquiry, unless we except the view
ttlstintained by Mr. Morgan, ih bis experiments oti the light fi*oui
combustion, Phil. Trans. 1785, No. li« He consictors light as
matter united to other bodies by attraction, blue rays having the
least, and rfid the greatest affihity. If this view of the subject
be admitted,' taiem pariiil^, more ^ed 'pai*ii(^les wbpid be
absorbed ^n .of any otl;.er coloured ray when io^pingtng upon a
surface. .

(63.) A liotiQe.hafi| v^ry r^c^ntly appeared (see Annuls qfPhu
losophy, S<4[it. .1^4). Pf 2.3^)* 9f .s.P.me prismatic exjperiments by



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)«M.3 ! Mir. Pe^Hm S^krlJ^himul Hed. tOS

Pr. S€«b66k; of Betfifi. The$id very itaportdnt j^e^^kei tetad
Id ^ttfsbHsk the coitdliaii4^ thai the ^dsitidHS of the mtaiiiiUi
jpottit of b#«t viiries in the speofriim aecqitiki^ K) the'l^^^lit^ ^
the di«T»er6iiig medium. With sdtne {>rism» it id eiliicitf^ itl th^
f^Utrn m dmage^ in those of crot<rii glftAi^ in die centre (tf th^ Jred>
«tid of fiittt glftfis beyond the fed^

nfhese eitperifiiente well expkin the dii^erepafieie^ b#lwe^
lUfferent observers^ though other catised before adve#t^d ii^ vS§f
have had ^otue share in producing those differendes.
- Iii viewing these results in reference to the nature dftha lie»i^
i$ig 0eets accompanying the rays of light, it beco£de» deeirskbte
U> inquire whether such changes in the heating power at differ^
Cffit parts of the spectrum are accompanied by dorresp^mdilig
irariations in the intensity of light : whether the gi^e^ter beat hi^
owing to a greater number of caloriftb and illun^itttttiAg rayi*
thi^own into the same space, owing to the differ^n^ law of dii^
peteiofi followed by the different refracting media. It iU'veiy
4€mbtfttl however whether there are any meaM of &sc^Qrt!3»ng
tins with ^rtainty and accuracy by means of the^ itlutniffMing
powers, so as to arrive at any such conclusion. But if i^ Weir^
ah^wn that the light is dispersed in different pi^Opcii^it)ns te liie
sfime part of the spectrum by different prisms, and thm ducfif
difibrence corresponded to the difference of heating poWer> B^.
Seebeok's reeaUg would in thi» case present no objectton td the
idea of the heating effect being inherent in the hght^ ^i resulUa^
s&erely from light so modified as t<^ become daloric>

The elaborate experiments of M. Frauenhof<^r on the i^efrac^tive
and di«pefsive powers of different substances (Echn* Phil. Jdnm.
Ko. 18, Art. 16), eichibit i?istances of a considerable alteration
in the relative dispersion of the rays by different mediae Thie
was ascertained with gteslt precision by mearte of the Well*'
defined bright and dark hne&i whibh he obserted crowding the
•peotrom. It would be extremely desirable to ascertain Whfrt
effect these lines have on the heating powers of the different
rays.

If this view of the subject were not established^ it might s^em
a natural inference that these results favour the idea of the hefdii
being due to a separate set of rays ; for if the heating poWeT in
Ae different parts of the spectrum can be made to vaiy, and th^
miB^imum can be thrown at pleasure into different coloured r&y§>
it might be argued that the effect must depend upon some ind^
pendent agent or set of rays distinct from the luminous rfeys.

Such a conclusion however is, perhaps, more than the feeta
win safely warrant. Those who have rejected the idea of sepa-
rate rays of heat have usually gone to the opposite ettfeme-, and
Mpposed the heat to be identical with the light ; and that the^
heating effbdt ia merely the dii^pk^ of the firame iigent, light, in*
another form. But is this the necessiairy altemiitive? th tmt&

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204 Mr. Powell an SolUr Light and Uedt. IMaaCh,

HO medium between identifying light witbheat, and maintaining
% totally separate set of rays ? It appears to me that if we reject
either one of these opinions, we are not by any means obliged
to adopt the other. Without identif;]^ins the two stents, or
without supposing them inseparably united, without conceiving
the heating power absolutely inherent in everjr particle of light,
and invariaole in intensity, except as the intensity of light
varies, on the one hand; or on the other hand, that the heat
consists of a distinct set of rays analogous to the rays of light;
we may admit it to be in some very close state of union, combi-
nation, or dependence, yet so as to be susceptible of variation
without a corresponding variation in the other effects of light*
And such indeed, antecedently to the inquiry here adverted to,
would seem the most natural and obvious way of considering the
matter ; because we are ignorant whether light be matter, or
whether heat be motion, does it follow that there is any neces-
sity for explaining the phenomena in which both agents seem
concerned, by assuming them to be one and the same thing, on
the one hand ; or by denying that there is any sort of union
between them, on the other ?

(640 T^o adopt a view of the subject which shall be a medium
between the two extreme theories hitherto adopted appears to
me not only to be what is most natural and most analogous to
the views we take of other natural phenomena, but what is
reouired by many strong facts.

To suppose that rays of heat exist distinct from those of lights
either in tne direct solar rays, or in the prismatic beam, requires
the supposition of a new and peculiar sort of radiant heat, as
different from common radiant heat as it is from light ; by which
means I do not see that we obtain any more satisfactory expla-
nation of the phenomena than we did before.

(66.) It is certain that whatever we suppose to be the state in
which the heat exists when it so inseparably accompanies the
sun's li^ht, there must be some peculiar circumstance in the
mode of its union which makes its effects sensible only under
some particular circumstances ; and under others endows it with
properties which heat in its simple radiant state does not possess.

In ordinary cases there is a direct communication of heat to
substances with which light comes in contact. This effect is
produced on all substances in some degree, but on some much
more than others ; and these are of a character widely different
from those on which simple radiant heat is known to produce its
greatest effects.

Heat accompanying light passes through the densest sub*
stances which are completely impervious to simple radiant heat
(unless first thoroughly heated), and yet produces less heating
effect on these than on any class of substances which are heated
at all by the impact of light.

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1825.} Mr. Fomtt on Solar light tmd Heat^ 205

From these and nnny more examples which might be adduced^
it is evident that heat accompanying solar light must be com*
pletely altered in its properties by the connexion subsisting
between them.

(66.) If we had any experimental proof of the materiality of
lights and should observe heating effects accompanying it, we
should not hesitate to say that they were nothing more than an
ordinary effect of a combination of heat with the material sub*
stance m question. But in the absence of such proof can we be
permitted thus to describe the phenomenon ? Did the question
mvolve no other difficulty than this, I should reply that as we
can define matter by no other tests than its observed properties,
it would be the proper course for the experimentalist to deduce
the nature of hght from its observed properties, and not to
describe those properties merely in conformity with its supposed
nature.. And observing real eflfects of ordinary heat, and findine
them coextensive with the luminous beam, I do not see any red
difficulty on this ground which should hinder us from describing
tiie phenomenon as a combination of heat with the luminous
particles..

It may be objected that to attribute such an union with heat
to light IS to assume the materiality of light, and thus to adopt
gratuitous suppositions.

It is never objected, however, that we make hypothetical
assumptions when we talk of ordinary matter possessing a
sensible temperature or latent heat^ 8cc. and yet what assumption
do we make in the case of Ught which is not made here ?

We conceive it allowable to say that ordinary matter is com-
bined with heat, yet if we come to consider the matter accu-
rately, it is only that we perceive a certain degree of solidity,
extension, &c. united with a certain figure, and at the same time
we find the sensation or effects of heat produced coextensively
with those other properties cognizable by our other senses^
Why then is it not allowable in the instance of light where wis
perceive a certain colour, extension, direction, &c. and heating
effects concomitant and coextensive with the display of those
properties, to say that light has heat in a similar sort of union
with it ?

(67.) In the preceding parts of these remarks, various proofs
have appeared of the close connexion subsisting between the
luminous rays and the heating effects accompanymg them, and
of the exact proportion followed so long as the lignt is of the
sdjne colour, and derived from the same source, .

If then we can show by experiment that heating powers
belong to light ; if these effects accompany light in a manner
and degree strictly analogous to a given class of those pheno-
mena which arise from what we call an uxiion of heat witn ordi-
nary matter ; why should we not be permitted to describe the
facts by expressions framed upon suoh analogy?

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809 Mr/F^wiailmSoUrtAghtmidfleif^ [M^Jte»j

. Tb^se aflecto which wq i»iU effacto of ealimc in Qfid^ary^ wit-
ter, pervade it in different w»ys, and are exhibited in aavaral
mxeU of union or connexion^ In order then to adopt wiUi ipm^
priety this mode of describing tlie calorific phenomena o£ UAk^
the chief point is to examine carefully wbetnerthe anajogy wes
hold good; and to show to what part of the pheoomena of b^
in its combination with ordinary matter, those of its union wil^
light aro to be compared.

The first and moat obvious idea is, ean the effects bo asmbed
to what we might call the high t$m^raiure of light?

Since light is known to pass through many very dense media»
^ communicate very little if any heat to Uiem, it might hm
inferred that it possesses no sensible temperature of its own ) hut
this inference is obviously of no force : for in passing throuf^
Iranaparent media, most of the lumincHsa particles are never m
contact with those of the medium, but paisa probably betwetn
them and that with inconceivable velocity $ so thaA whatever
heat they may possess, they are ineapable of ^ommuoioating \U
fiome few ri^a are stopped and absorbed by the medium aoii
more as it possesses a less perfect transparency ; and in proper^
lion as this is the case, we know tljat heat is always communi-
i;i^ted,nnd all transparent bodies, after being some time exjpoaed
to the sun's rays, become heated.

. When we come to consider the different development of its
heating power on bodies of different colour, the effi^to are
totally unlike those of temperature. On this principle, the hea**
ting effect would depend upon the impact of light rather than
it(3 absorption, and it should not be ^eater on a blaok than on
a white snrfaee. But perhaps the difference of calorific powet
jn the prismatic rays is the strongest evidence against attributinff
the effect to temperature ; for in this case how could such
diffifrrence of temperature be maintained, supposing it could be
originfdly communicated, when the rays are aJl in contact, and
moving with equal velocities ?

From these consideration^, it would follow that the heatmus);
tfKist in some state of combiaation with the light, moi« intimate
and mmre connected with its changes' and modifications than
that belonging to heat of temperature.

. In order to be the better prepared for following up this
innuii^, I propose shortly to bring forward some exppnm^nls
nnd ^onduEiions, which are supplemmitary to some rese^riAes
an. Vi^Ait and heat fi-om terrestrial sources latelj^ r^ad before the
RoyfQ Society. (See reports of the Royal Society, Annab, ^



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. tSe&T " ' On the Cilma^ ^.iklAUikliMian World. 9BB



Article VII.

On the Climate of the Antediluvian Worlds andits Independgnee
. 0/ Solar Jriflummi ^^d on the Formation of Granite. By Sir
Alexander Crichton, Knight, St. W. FRS, &c.

(Concludttdfirom^pAOS.)

Having endeavoured to prove, in the first part of this essay,
that the laws of vitality, especially those to which the life of
Vegetables is subjected, afford an almost certain rule for judging
iftf lempeWLtuFfe ; and having shown by the character of the fossu
msMiiBsrof the earliest plants of which we have any knowledge^
that an uniformly high temperature exerted' its influence over
every part of the globe where they are found, I passed to the
eoBsideratioQ of other geological facts, all of which are connected
with the same subject, such as the similarity of the fossil
remains in the transition and mountain limestone, and the difi.
ferent temperature of hot springs according to their respective
depths, Bfid the heat of waters which issue from rocks m deep
mines. Prom all these facts, the conclusion appears to be incr
vitable, that iii the very early periods of time, the heat of ti^e
earth was greater and mote uniformly diffused, than can fe^
accounted for by solar influence.

The analogy between crystalline substances (which we kno\^
to be of igneous origin) and granite, and the recent discoveries
ef Mr. Mitcherlich, were added as strong arguments in Support
^f the doctrine. As chemical science Has how opened a roa4
by which we may account in a natural manner for the fermatioqt
Of granite, and also for the high temperature which resulted
from its immediate production, we need not have recourse to
ftny Overstrained conjecture to account for the fact, such as ih^
BOtioii of a great and unaccountable change in the direction of
the earth's axis, an idea which is totally unsupported by analogy
or reason. V

It is not possible for the imagination to conceive a state of
chaos and disorder and of intense heat, like that which must
have happened during the rapid ignition ^nd qxidatioii of the
metallic nucleus. Whether granite b^ the stratum of oxidize4
metals nearest the nucleus is very dopbtful. Fronj the exami-
nation of many collections of volcanic ejections, I am mi^ch
inclined to think that some micaceous beds lie under sraQite.*

« The v^netj^fi «f iiati^ra} piiner^l <^m|Kmn4s w}ii^ m^^m ^ effs$ri^ ^m ff
mica fire Bumerous. If we except those oopapound.ftubstance| whiph ^ssumf t)if.^?lffi
•f(j;aR»Ct, t^ere tat none so diversified in their chemical constitution^ ami . tfa^rdtn^

9f ii4kMiM oTfr Uf w ai» c^ivecr^ with oiim f9^ ^m9^ o^ . iP^ inlwcMI
rock# im>ear to have been ejected fronji v ef^^vius on i^ (ir$t l^urftW V?^ M wf jM^M
rfme im ^et» of gtanhe were also thrown out;



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206 Sir A. Crichim m tht [MAKcd,

If the supposition be well founded, that granite and its asso-
ciates are oi igneous origin, inasmuch as mey are the result of
quick oxidation and fusion, there ought not to be any great con-
stancy in the super-position or juxta-position of these rocks, for
it is clear that they may have varied according to the preponde-
rance of any one metal, or any number of metals, in any given
portion of the metallic nucleus.

Other causes appear to have co-operated with this in produc-
ing a considerable variety in the mechanical aggregation of the
primitive rocks, as well as in their forms and relative position.

In a paper expressly written on antediluvian temperature, it
cannot be expected that I should enter fully into an examination
of all these causes ; yet a cursory view of some of them is una-
voidable for the elucidation of what is to follow.

The immediate effect of the oxidating process of the metallic
mass would necessarily be a violent ebullition, agitation, and
evaporation, ofthe surrounding fluid, and also the formation of
various ^ases and gaseous oxides. Although the extinction of
the ignition would result as soon as a crust of earthy oxides (the
primitive rocks) was formed, yet during the consolidation of
these, the action of the watery vapour, included between the
intensely heated nucleus and the hot involucrum, would give an
elastic K)rce to the included vapour commensurate with its heat.
When to this supposition is added the phenomena resulting from
causes which we have every reason to believe to be similar, such
as the sudden elevation of islands and of great tracts of land ou
the coasts, as well as the equally sudden depression of other
tracts of continents, we^ are furnished with strong reasons for
believing that many parts of the imperfectly solid and still
heated granitic mass must have been elevated and rent in
various places, giving birth to groups and chains of granitic
mountains, the peaks of which, although greatly worn down
since that period, still exhibit a character of ruggedness and
rupture which peculiarly coincides with the theory.

The following account of the highest granitic peak in the
Upper Oroonka district, taken from the j ustly celebrated Baron
Humbold's excellent work, entitled "rersonal Narrative," is
appropriate to the present subject, and so singularly interesting
in itself, as to justify its insertion in this place. I may ]>reniise
that the granitic peak called Duida is estimated by this scientific
traveller at 1,300 toises above the level of the sea«

'^ The granitic summit of Duida is so nearly perpendicular
that the uidians have vainly attempted the ascent. It is known
that mountains the least elevated are sometimes the most inac-
cessible. At the beginning and at the end ofthe rainy season,
small flames, which seem to change their place, are seen on the
t^ of Duida. This phenomenon, which it is difficult to doubt
en account ofthe agreetnent in the testimony concerning it* ha»



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1825.] Climate aftheAnttdiluman World. 209

giv^n this mountain the imprdper name of 'a voteftno^ As it
stands nearly alone, it might be supposed that lightning from
time to time sets fire to Uie brushwood; but this supposition
loses its probability when we reflect on the extreme difificul^
with which plants are set on fire in these damp climates. It
must be observed, also, that these little flames are said to appear
often where the rock seems scarcely covered with turf, and that
the same igneous phenomena are displayed on days entirely
exempt from storms on the summit of Guaraco, or Murcielago»
a hill opposite the mouth of the Rio Tamatama, on the southern
bank of the Oroonoko. This hill is scarcely elevated 100 toises
above the neighbouring plains. If the assertions of the natives
be true, it is probable tnat some subterraneous cause exists in
Duinaand Guaraco, that produces these flames ; for they never
appear in the lofty neighbouring mountains of Jao and Mara-
guanca, so often wrapped in electric storms.

'^ The first cause of these igneous phenomena is at immense
depths below the secondary rocks in the primitive formations :
the rains and the decomposition of water act only a secondary
part. Tlie hottest springs of t/ie globe issue immediately jfrom
granite. Petroleum gushes from mica schist, and fright-
ful detonations are heard at Encaramada, between the rivers
Arauca and Cuchivero, in the midst of the granitic soil of the
Oroonoko and the Sierra Parima. Here, as every where else on
the globe, the focus of volcanos is in the most ancient strata ;
and it appears that an intimate connexion exists between the
great phenomena that heave up and liquefy the crust of our
planet and those igneous meteors which are seen from time to
time on its surface, and which from their littleness we are
tempted to attribute solely to the influence of the atmosphere.**
— (See Personal Narrative, vol, v, p. 662 et seq. and vol. ii.
chap. 6, p. 291, and vol. iv. chap. 14, p. 46.)

I n the first part of this essay, it was stated in a general way, on
the authority of Baron Humboldt, that the thermal springs of
South America received their heat from the primitive rocks.
The following passages are remarkable : — Speaking of thermal
springs in the neighbourhood of the lake of Valencia, he says,
'* These springs gush out at three points of the gra^uVtc cordillera
of the coast; near Onato, between Turmero and Maracay ; near
Murisa to the north-east of the Hacienda de Cura; and near
Les Trencheras, on the road from Nueva Valencia to Porto
Cabello. I could examine with care only the thermal waters of
Mariara and Las Trencheras." The mountains of Mariara, be
says, " form a vast amphitheatre, composed of perpendicular
rocks, crowned by peaks with rugged summits." The granite
which constitutes the peak of Gala vera is separated, he assures
us, by perpendicular fissures into prismatic masses.

These extracts I have inserted not with a view of proving any

New Smes, vol. ix. p

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file 'aiirA\Cfkkimi6kH^ [MUfcft;

fttinrogy beiW^i^n this ig66<)tid ph^ttottient of Duida and voka^
tioSf but riderely to juntify the iissertion concemmg the deep
fissures of gmnitid peaks^ and the h^at derived fVom their foun^
dations : wheffe it tnay be sujiposed there is a vicinity to die
^till hot nucleus of the earth.

The softening, elevation, and rapture, of the first formed gra*»
nitic mountains, and the actioil of the agitated dceati, would pro«-
duce the separation of an infinite number of minute grains of
the newly-formed crystalline substances^ many of which WBtM
be suspended mechanically for a longer or shorter time aeeord**
ing to their respective gravity on the one hand» add the greater
or lesser agitation of the waters on the other.

Some earthy oxides, such ad the argillabeous oxide or olay»
which have a kind 6f mechamcal attraction for water, which 16
not perfectly underalood, would be longer suspended than the
minute crystals of n^ttia, amphibole> quarts, or feldspar, and
would be precipitated) all Other things being alike, at a later
period, and hence in the generality of cases gneiss hes under
the argillaceous beds and rocks where these are found.

The presence of anthracite in the fissures of primitive rocks
demonstrates that carbon was an elementary ingredient in the
nucleus of the elemeMary globe ; and it is therefore reasonable
to conclude that, during the state of ignition, it would attract
oxygen from the decomposition of the water, and form carbonie
acid, which, after combining with the waters, would render it a
solvent for all such metallic oxides as have a powerful attraction
for it, and which are rendered more soluble through its agency,
such as lime (oxide of calcium), and magnesia (oxide of magne*
sium).

The precipitation of such carbonated oxides (limestone and
magnesian rocks) would depend chiefly on the agency of three
well known caused; Jirst, the continued formation of more
otides than the waters could dissolve ; secondly, the diminution
of temperature ; and thirdly, the effects of evaporation.



Online LibraryThomas ThomsonThe Annals of philosophy → online text (page 24 of 52)