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work on the geographical extension of the trade winds and
monsoons. It is surprising that in his magnetic expeditions
he makes no mention of the ^^ law of the winds" — so
important for the whole of meteorology, — as its general
features had been recognised by Bacon, and by Johannes
Christian Sturm of Hippolstein, who, according to Brewster,
^524 J was the true discoverer of the differential thermometer.
In the brilliant period of the foundation of '^ mathematical
natural philosophy," attempts to investigate the moisture of
the atmosphere in its connection with variations of tempera-
ture, and with the direction of the wind, were not wanting.
The Academia del Cimento conceived the happy idea of
dd;ermining the quantity of vapour by evaporation and

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THE TJNIVEBSE. — ^DISCOTEBIES IN THE CELESTLAX SPACES. 839

-precipitation. The oldest Florentine hygrometer was accord
ingly a condensation hygrometer, an apparatus in which the
quantity of precipitated water which ran ofif was determined
by its weight. (®^) To this condensation hygrometer, which,
aided by the ideas of Le Eoy, has gradually led in our own
days to the exact psychrometric methods of Dalton, Danidl,
and Auguste, there were added, according to the example
previously set by Leonardo da Vinci, (^^6) h^q absorption
hygrometers made of animal or vegetable substances, of
Santori (1625), Torricelli (1626), and Molineux. Catgut,
and the beards of a wild oat, were used almost at th^ same
time. Instruments of this kind, founded on the absorption
of. the aqueous vapour contained in the atmosphere by organic
substances, were provided with indexes and counterpoises,
and were very similar in construction to Saassure^s and
Deluc's hair and whalebone hygrometers; but the instru-
ments of the 17th century were deficient in the determina-
tion of fixed dry and wet points, so necessary for the
comparison and understanding of the results. This desi-
deratum was at last supplied by Eegnault, but without
reference to the variation which might be occasioned by time
in the susceptibility of the hygrometric substances employed.
Kctet, (527) however, found that the hair of a Guanche
mummy from TenerifFe, which might be a thousand years
old, employed in a Saussure^s hygrometer^ still possessed a
satisfactory degree of sensibility.

Electric action was recognised by William Gilbert as
the operation of a natural force or power allied to magnetism.
The book in which this view was first enounced, and even
in which the terms '^ electric force,'' ''electric emanations,''

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840 XSOCEB IN tHB fWPtOVX OV THB OOlTIBICPIiATICRr COF

and '^ electric atiTaction''^ {^^) were fiw* rinployed, is iiie
work to whidi I have abreadj so often wsbimA, pobtished
in 16&0, and entitled ''Phj&okgj of M^nete, and (rf &
Earth aa a great Magnet^ (de magxio iziagneie tdhire).
'^ The faculty of attracting^ when rubbed^ ligjht aubstanees^
whatever mi^ be their natare, does not/' wys Gflberi^
'^bekoig exdusively to afiib(^^ whieh is a condensed earth-
jnice thrown np by the waves of the sea, and in which %]i^
insects^ ants^ and worms>^ are inclosed as in perpetual tombs,
(aetemis sepulchris). The attracting power belongs to a whole
class, of very different substances; 8U<^ as ^ass^ sa^hm^
sealing wax and all resinB^ rock crystal, and all kinds of
peciou^ stones^ alum and rode salt/' The strengtli of the
electricity emted was measured by GSbert by means of an
iron needle (not very somll), movix^ freely on a point (ver-
sorium electrieam) : v^ aimilar to the scpparatna em^xbyed
by Hatty and by Brewster, in trying the dcctridty exdted
in different minerals by wannth and friction.
. Gilbert says farther on, that ''fiictioii is found to prodnce
more ^ect in diy than in dan^ air, and that mbbing w]&
silk is most advantageous. Tbe terrestrial globe is held
together as by an dedrie fc^roe (?) (Globus tdkiris perse
dectrice congregatur et cdiseret); for the deetric action
tends to produce the oohenon at msrfier (motos dectricns
est motus coaoervatioms materis)/^ ' In these d»cure
axioms is expressed the view of a tdluric electricity, — the
manifestation dt a force like magnetism belonging to matter
^ such. Nothing was yet add of repnldon, or of the
difference between insulators and conduetcn.
The ingeoious discoverer of the aar-pump^ Otto vott

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THB IJlfrVBKSB. — ^MSCOTBBIBS^ IN THE CBLBSTIAL SPACES. 341

Gu^rike^ was the first who obseived mote thaa mere pheiio-
mesm of attraetioD, In his exp^iments, inade with a^
tubbed cake of siilphnr, he recogaised phenomena rf
l^alsion, which affcerwaids led to a knowledge of the laws
of the fiph^!e ot action and of t^ distaribution of electricity.
He heard the first sound and saw the first light in artificiaSy
elicited electridfy. In an experiment made by Newton m
1675; the fioEst traces of the " electric cktrge^' m a rubbed
plate of glass Wiwe seen. {^'^} We have here sought otffc
only the first germs of the science of eleetriciiy> whidi^ in
its great mid singolariy retarded devdopm^, has not only
become one of the most important parts of meteorology,
•but also, sQice we have learned tiiat magnetism is one of ^
snsmifold forms in which electricity discloses rtsdif^ h.t»
deared up to us so much belonging to the internal operaflioa
ot terrestrial powers or forces.

^ Ahhough Wall in 1708, Steij^ea Gray in 1784/ ^id
Nollet, conjectured the identity of friction electeicaty and of
lightDing> yet tiie expmmeutal certainty was first attamed
jabout the middle of tike Idth e^tory by the successM
endearonrs ci the ilhistrions Benjamin IFrankhn. From
ihis epod. the dectric process passed from the domain of
speculative {^ysies to that of tl^ cosmical eonteinjdb,tion <d[
»ature — ^from the diamber of the student to the open ficJd,
Tbs doctrine of dectridty, l&e that ol optics smd of mstg-
netism, has had loi^ periods of exceedingly dow develcqpmeci,
until in these A?ee Immches the labours of Ibnmklin aaid
Tolto, Ttiomas Young and Msim, Oersted and YvamiSiaf,
•roused theor eotemporsffies to an admirable activity. He
progiwn of luiman knowledge is genan% ccnineeted wi^
abcnutionsof slumber and of suddenly sMrakened activityv

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842 EPOCHS IN THE HI8T0EY OF THE CONTBMPLA.TIOM Of

. But if, as we have already remarked, by the invention of
appropriate although still very imperfect physical instru-
ments, and by the sagacity of Galileo, Torricelli, and the
members of the Accademia del Cimento, the relations of
temperature, the variations of the atmospheric pressure, and
the quantity of vapour in the air, became objects of imme-
diate research; on the other hand, all. that regards the
chemical composition of the atmosphere remained wrapped
in obscurity. The foundations of ^' pneumatic chemistry"
were indeed laid by Johann Baptist van Helmont and Jean
Bay, in the first half, — and by Hooke, Mayow, Boyle, and
the dogmatising Becher in the latter half of the 17th
century ; but however striking was the correct apprehensioit
of particular and important phenomena, yet the insight into
their connection was wanting. The old beUef in tho
elementary simpUcity of the air which acts in combustion,
in the oxydation of metals, and in respiration, formed an
obstacle difficult to be overcome.

The inflammable or light-extinguishing kinds of gas oc-
curring in caves and mines (the ^'spiritus letales" of PKny),
and the escape of these gases in the shape of bubbles in marshes
and mineral springs, had already arrested the attention of the
Erfurt Benedictine monk Basilius Valentinus, who probably
belonged to the close of the 15th century, and of Libavius,
an admirer of Paracelsus, in 1612. Comparisons were drawn
between what was accidentally remarked in alchemistic labo-
ratories, and what was seen to have been prepared in the great
Itboratories of nature, especially in the interior of the earth.
Mining operations in beds rich in ore, (particularly such as
contained pyrites which become heated by oxydation and

''^ntact electricity), led to anticipations of the chemical



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THE TTNIVEIISE. — DISCOVEMBJ TtS THE CELESTIAL SPACES. S4B

tdations between metals, acids, and the air which gained
access from without. Paracelsus, whose fancies belong to
the epoch of the first conquests in America, already remarked
the disengagement of gas when iron was dissolved in sul-
phuric add. Van Helmont, who first made use of the
word " gas/' distinguishes gases from atmospheric air, and
also, on account of their non-condensability, from vapours.
He regards the clouds a.^ vapours, which, when the sky is
very clear, are changed into gas ^^by cold and by the
influence of the heavenly bodies." Gras, he says, can only
become water when it has previously been retransformed
into vapour. These views of meteorological processes be-
longed to the first half of the 17th century. Van Hehnont
■was not yet acquainted with the simple means of receiving
and separating his " Gas sylvestre," (under which name he
included all uninflammable gases diflerent from pure atmo-
spheric air, and incapable of supporting flame and respira-
tion) ; yet he made alight bum in a vessel having its mouth
in water, and remarked that ad the flame ,went out, the water
entered, and the " volume of air" diminished. Van Hel-
mont also sought to demonstrate by determinations of weight,
(which we find already in Cardanus), that all the solid parts
of plants are formed from water.

The mediseval alchemistic opinions of the composition of
metals, and of their combustion in air whereby their bril-
liancy was destroyed, incited to the examination of what took
place diiring the process, and of the changes undergone by
the metals themselves, and by the air in contact with them.
Cardanus had ahready become aware in 1553 of the increase
of weight that takesplace during the oxidation of lead, and,
-quite in the spirit of the phlogistic hypothesis, had ascribed

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SM XFOOHS IK THB filSTO&y Ol? TH£ OONTEMPlATjEOK OF -

tttotheesciq^of a ^'eelestial^eiysubstaace^^ causiiiglevi][yi
fait it was Bot until ei^iyjears afta^ards, that Jean Bey, a^
eKceedinglj skilful experimenter at Bergeiac, who had exr
jpdned with great aopuracy tiieincieaseof weight daring thf
calcination of lead^ tin and antimony, enounoed the important
sesult that the increase of weight was to be attributed to the
aooeasion of air to the metallic calx^ sayings ^^ Je leepondg
«t aonstiens gloriensem^ que ce Borcroit de poids vknt
dfi Tair qui dans le vase a 6st^ espessi.^' (^30)

Men had now entered on the path which was to xxmduct
to the ch^nistry of our days, and through it to tiie knowledge
af a great oosmical phenomenou^ the connection between tiie
«xyg^i of Hie atmosphere and the life of plants. But Hob
ONBabiaatip^ <^ ideas wipch next pres^ted itself to distin-
gnished men was of a singularly complicated nature. Towards
Hm end of the llik century there arose^ — obscurely with
Hooka in his Micrographia (1665), and more distincily wiiji
Mkyow (1669,) and WiUis (1671),— a belief in tiie existence
«f nitro^aenal pavtides, (spiritus nitro-aereus, pabulum nitro-
BBBi), — identicsd wiiii those which are fixed in 8altpetre,-r
ecmtained in the air and constitui^ing the neoessaiy conditioii
of combustion. '^ It. was stated that the extinction of flame
in a close space does not take p]aoe &om the air being <wei;-
eaturated with vapours pi?oceeding from the burning body,
but iliat this extinction is a consequence of the entire ab-
Borption of thenitro-aerialpartides ('^s^ritus nitro-aeteus'*)
which the air at first contained/^ The suddenly increased
glow wh^ meiting saltpetre (enaittiig oxygen) is strewed
upon OiB coals, and the exudation oi saU^etre on day walls
in contact with the atmosphere, appear to h^ve conduced to
^hi» opinion. According to Mayow, the re^iration Ui

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THB UNTTSRSS. — DISCOVEEIES IN THE CKLBSTLIL SPACES. 845

scdmsals^ of wMch tbe production of ammai h^, and tht
ocnrver^on of bladt into red blood are fte resnlt, ttie
processes of comb^ostion and the calckiation of metals^ ar6
all dq9endent on these nitro-aerial particles of the atmosph^e-.
in the antiphlogistK chemistry^ they play nearly the part dF
oxygen. Tie cantioady doubting Robert Boyle recognised
tiiat the presence of a c^ain constituent <^ atmospheric air
is necessary to the process of combustion ; but he r^nained
uoeertain as to its nitrous nature.

Oxygen was to Hooke and Mayow an ideal ol^ect or a
£dioQ of the imagination. The acute cheniist and Tegetal^le
physblc^ist Hales^ in 1727^ first saw oxyg^ escape as gas
in large quai^aties froin ike lead whik^ he calcined undeic
an intense heat. He saw the gas escape^ but without ex-
amining its natnre or ranaiking the vividness of i^ flame
ooeasioned by it. Hales did not divme the importance of
the substance which he had produced. The vind «mlati(m
of li^t in bodies burning in oxygen gas, and its {nroperties,
were discovered, as many bdiieve quite independently^ ('^
—by Priesdey in 177 W774, by Scheelein 1774.1775, and
by Lavoisier and T^ndabe m 1775.

The eomtafucements ti pneomatic chemistiy have been
touched upon in these pages in ifaeir historic connectioa^
because^ like &e feeUe begmnii^ of dectric sctence, they
prepared the way for tihe edarged views, which the succeed-
ing e^itnry Ins been able to form of the constitution of tiie
atmoq»hffl» and of its meteordbgical variations. The idea
of ^ecifioally-diBtinet gases was n&vet perfecUy dear to
those who in'tiie seventeeafli cmitury produced those gases.
Men began i^iuh to attribute the difkreaee between
atmosphetic air and the irrespirable^ Ij^^t-extinguirfiing, or

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846 EPOCHS IK THE HISTOBT OF THE CONTEMPLATION OF

inflammable gases^ exclusively to the admixture of certaiiK
vapours. Black and Cavendish first shewed in 1766 that
carbonic acid (fixed air) and hydrogen (combustible air) aie
specifically distinct aeriform fluids. So long had the ancient
teUef in the elementary simphcity of the atmosphere impeded
the progress of knowledge. The final investigation of the
chemical composition of the atmosphere^ by a most accurate
determination of the quantitative relations of its constituent
parts by Boussingault and DumaSj is one of the brilliant
points of modem meteorology.

The extension of physical and chemical knowledge, which
lias been here described in a fragmentary manner, could not
remain without influence on the early progress of Geology.
A great part of the geological questions with the solution of
which our age is occupied, were stirred by a man of the
most comprehensive knowledge, the great Danish anatomist
Nicolaus Steno (Stenson) in the service of the Grand Duke
(if Tuscany, by an English physician Martin Lister, and by
'^ Newton's worthy rival,'' (s^^) Eobert Hooke. Steno's
merits in respect to the superposition of rocks have been de-
veloped by me more fully in another work. {^^^) Previously
to this period, and towards the end of the fifteenth century,
Leonardo da Vinci, probably in laying out the canals in
Lombardy which cut through alluvium and tertiary strata, —
Fracastoro in 1517, on the occasion of seeing rocky strata
containing fossil fish accidentally uncovered at Monte Bolca
near Verona, — and Bernard PaUssy in his investigations
respecting fountains, — ^had recognised the traces of a formar
oceanic world of animal life. Leonardo, as if with the pre-
sentiment of a more philosophical division of animal forms,
terms the shells " animali che hanno I'ossa di fiiori/' Steno,

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THE TTNTVEBSE. — ^DISCOVBEIES IN THE CBLBSTIAL SPACES. 3 47

in his work on the substances contained in rocks^ (de
Solido intra Solidum naturaliter contento) (1669), distin-
g^oishes ''tocky strata (primitive?), hardened before the
existence of plants and animals, and, therefore, never con-
taining organic remains, from sedimentary strata (turbidi
maris sedim^ta sibi invicem imposita), which alternate with
etob. other and cover those other sirata first spoken of. All
deposited strata containing fossils were originally horizontal.
Tlieir inclination has arisen partly from the outbreak of sub-
terranean vapours which the central heat (ignis in medio
terrse) produces, and partly by the giving way of lower sup-
porting strata. (*^) The valleys are the result of the falling
in, consequent on the removal of support.^^

Steno's theory of the formation of valleys is that of Deluc^

wbereas Leonardo da Vinci, {^^^) like Cuvier, considers the

valleys as formed by the action of running water. In the

geological character of the ground in Tuscany, Steno thought

he recognised revolutions which must be attributed to sul

great natural epochs, (sex sunt distinctse Etrunse facies, ex

prsesenti fade Etrurise coUectse) : at six recurring period

the sea had broken in, and after continuipg for a long time

to cover the interior of the country, had withdrawn again

within its ancient limits. Steno did not, however, regard

all petrifactions as belonging to the sea; he distinguishes

between pelagic and fresh-water petrifactions. Scilla, in

1670, gave drawings of the petrifactions or fossils of

Calabria and Malta : our great zoologist and anatomist

Johannes Mtiller has recognised among the latter the oldest

drawing of the teeth of the gigantic Hydrarchus of Alabama

(the Zeuglodon Cetoides of Owen), a mammal of the greai

VOL. II. 2 A

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S48 EPOCSS W THE HI8T0BY 07 THE COKlSamATIOK OY

order of iJie Cetaceoe; (**^) tiie crown cS these teeth is
lormed like those of seals.

Lkter, as earlj as 1678^ made the impoitai^ stsfc^fi^^
that each kind of rock is characterised by its own fossils^
and that 'Hhe species (d Murex, Telliila andl^hujB, which
are found in the quarries of N(Hr<hBnipl(»i8hfire^ do^ ifideed^
resemble those of the piresent sea^ but wh^i dkNtely exainigaed
are found to differ from them/' ''They aw/' be B»d,
''specifically MereiA/' (^) In the ttien imperfect state of
desmptive morphology, strict proofis of the justness of fliese
grand anticipations or conjectures could not indeed be gi^^^i.
We here pdint out an early dawning and soon extinguished
light, anterior to the great psJeontdogicel laboun of Cuvier
«nd AlexandOT Brongniart wWdi have given a new fonn to
flie geology of the sedimentary formations. {^^) lAstetj
attentive to the regular suocesskm o[ strata hi England, was
the &st who felt th^ want of geological maps. Although
these phenomena in their connexion with ancient inundations
(single or repeated) attracted interest and attention, and,
mingling togeth^ belief and knowledge, produced in
England ihe *' systems'' oi Eay, Woodward, Burnet, and
Whiston, yet, from the entire want of mineralogical cBs-
tinction of the constituent parts oi compound rocks, all that
relates to the crystalline and massive miiptivo ro^ aad
their transformations remained unstudied. NotwfthstandiBg
the assumption of a central heat in the globe, earthquakes,
thermal springs, and volcanic eruptions, were not regarded
as the results oi Ihe reaction of the jdanet againi^ its
external erust, but were ascribed to such small local causes,
as, for example, the spontaneous combustion <^ beds #f

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THX VNTVERSL-f^-OnSOO^nUBQIS IN 'THB CELESTIAL SPACaS. 849

l^tes. Erffli expenments made in eport by Lemeiy in tbe
jear 1700 exerted a longooontinued mflnence on vokaoie
iheoriesj althoa^ these might have been raised to BM»f»
g^ieral views I^ the imaginative Protogeea of LeflbnitB
(1680).

Tlie ProtogBBai which is sometimes more poetic than the
siany metarieal attempts of the same philosopher which haive
lecentlj beeii brought to lights (^^) teaches the 8c<^-
eation of the cavernous^ j^wing^ and once self4nminons
enust of the earth ;-*^€ gradual cooling of the heat-
radiating soifiice ^ivdoped in v^^urs; — ^the condensa-
tion^ and precipitation into water^ of the gradually cooled
atnto^hore of vapour ; - ^the lowerii^g of the sea by the
sinking of its waters into internal hdlows in the ear&;*«<*
and finally the fidling in of tibese caves or hollows causing
the indinati(Hi of the strata. . The physical part of these
wild fancies ofiBors some traits which, to tibe adherents of our
modem and every way more advanced geological sdence,
will not appear altogether deserving at rejection. Such are,
the trausference of heat in the interior of the globe, and
Hid cooling by radiation bom the surface; the existence (tf
an atmosphere of vapour; the pressure exerted by these
vapours upon the strata during their consolidation; and the
double origin of the masses as either fdsed and solidified or
precipitated firom the waters. The typical eharactor and
mineral diffsrences of rocks, i. e. the associations of cer-
tain substances, chiefly crystalline, recurring in the most
distant r^ons of the earth, are as little spoken of in the
Protogsea as in Hookers geognostical views. In the last
named writer, also, physical speculations on the operation
rf nAterranean forces in earthquakes, in the «i#^9L^Jfele



850 SPOCHS IN THB HISTOEY OF THB OONTEMPLATIOK OF

tion of the bottom of the sea and of coast districts^ and in
the formation of mountains and islands^ predominate. The
nature of the organic remains of the ancient world even led
Hooke to form a conjecture that the Temperate Zone must
once have enjoyed the temperature of a tropical climate.

We have still to speak of the greatest of all geognostical
phenomena^ the Mathematical !Figure of the Earthy in
which we recognise as in a mirror the primitive condition of
fluidity of the rotating mass^ and its solidification intotis
present form of the terrestrial spheroid. The %ure of the
earth was sketched theoretically in its general outlines
at the end of the seventeenth century, although the
numerical ratio of the polar and equatorial diameters was
not assigned with accuracy. Picard^s measurement of a
degree, executed with measuring instruments which he had
himself improved (1670), is the more deserving of r^ard,
because it first induced Newton to resume with renewed zeal
the theory of gravitation, which he had already discovered
in 1666 and had subsequently neglected : it offered to that
profound and successful investigator, the means of demon*
gtrating the manner in which the attraction of the earth
maintained in her orbit the moon impelled onward by the
centrifngal force. The much earlier recognised fact of the
flattening of the poles of Jupiter (**®) had, it is supposed,
led Newton to reflect on the cause of such a departure from
sphericity. The experiments on the length of the seconds'
pendulum made at Cayenne by Richer in 1673, and on the
west coast of Africa by Varin, had been preceded by others
less decisive (^*^) made in London, I^yons, and Bologna,
including a difference of 7° of latitude. The decrease of
gravity from the pole to the equator, which had long been

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THE X7NIVEBSE. — DISGOYEBIES IN THE CELESTIAL SPACES. 851

denied even by Kcard, was now generally admitted . Newton
tecognised the compression of the earth at the poles as a
lesult of its rotation : he even ventured, upon the assump-
tion of homogeneity of mass, to assign the amount of the
compression. It remained for the comparison of degrees
measured in the eighteenth and nineteenth centuries under
the equator, near the North Pole, and in the temperate zones
of both hemispheres, to furnish a more correct deduction of
the mean compression, or the true figure of the earth. As
has already been remarked in the Picture of Nature in the
first volume of the present work, (5*^) the existence of the
compression announces of itseK what may be termed the
most ancient geognostical event, viz. the state of general
fluidity of the planet, and its progressive solidification.

We commenced the description of the great epoch of
Galileo and Kepler, Newton and Leibnitz, with the dis-
coveries made in the celestial spaces by the aid of the newly
invented telescope ; we terminate it with the figure of the
earth as then recognised from theoretical considerations.
'^ Newton attained to the explanation of the system of the
Universe, because he succeeded in discovering the force (**^)
of whose operation the Keplerian laws are the necessary
oonsequences, and which could not but correspond to the
phenomena, since those laws corresponded to and foretold



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