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altitude.

Fields cissitudes in

zone.

Verest (402.) Such are the lower limits* assigned to the rocks, and fix their roots where there appears to be but Meteor. ology. altitude of this magnificent plane, by the celebrated little soil; and the avalanches bring down whole forests

ology men whose names are recorded in the Table. If, how- in their overwhelming course, and dash the cedars into Osallations

ever, we stop our inquiries at this point, we shall leave splinters. many interesting portions of the problem unresolved. (405.) But much more striking vicissitudes will be Striking via The plane of the perpetual snows does not maintain a found as we advance into the temperate zone. constant elevation in the same latitude, but varies with of snow of an enormous width are alternately melted temperate the vicissitudes of the seasons, rising during the heat of and congealed, creating in the lapse of time those summer, and sinking by the cold of winter; changing mighty glaciers, which by their varied and gigantic also from one summer to another, as alterations are forms impart so much sublimity to the Alps. experienced in the temperatures below.

(406.) In order that glaciers should exist on a moun- Glaciers. (403.) If we first direct our attention to the Equa- tain, it must rise considerably above the limit of the pertorial regions, we shall discover some small oscillations petual snows. Prodigious masses of ice are also necesto exist in the altitude of the perpetual snows. To the sary for their formation, and an enormous pressure must mountaineerst of the Andes, the limit of the perpetual act from above, to force the inferior parts of the icy vosnows presents a phenomenon of a very constant kind; lumes into the valleys below. Hence the frozen masses and to their uncultivated minds, the silvery line seems precipitated by an avalanche, form groups below the lower to run through the enormous groups of their mountains, limit of perpetual snow. In this position they undergo but in one continued horizontal plane : the greatness of the little change during the lapse of centuries; the altera- Of the Alps. distance preventing them from observing those small tions produced by the gradual thaw being more than oscillations of altitude, which the more refined inquiries compensated by other masses formed in the cold reposiof the Philosopher have disclosed. This close approxi- tories above, and thence precipitated to the valleys bemation to uniformity arises from the equality of tem- low. Hence it is that travellers have remarked the perature existing in the different strata of the atmo- successive invasions of the Valley of Chamouny, by the sphere; and accordingly it is found that the utmost avalanches that have descended from Mont Blanc and amount of the oscillation of the perpetual snows in the adjoining peaks. It is worthy, also, of remark, that these regions does not exceed 30 fathoms, 5 and at the the five glaciers which have forced their way into the Equator itself rarely amounts to half that quantity. It beautiful valley just mentioned, are separated from each is often, indeed, insensible, notwithstanding the small other, by forests, corn-fields, and meadows,-large tracts differences of temperature which are found to exist of ice mingling with the cheerful fruits of cultivation. between the season of rain and that of great dryness.

(407.) The finest glaciers in Norway, are those pro- of Norway. (404.) If we pass, however, from the Equatorial ceeding from the chain of the Justedals Eisberge. regions, we shall discover new conditions presented They are known to the inhabitants by the name of for investigation. No longer confined to the feeble Jis-Braeer, and at times are much dreaded by them on

oscillations we have referred to, we shall find all the account of the rapidity of their motion, which exceed You mais attendant phenomena become more irregular. In the that of the glaciers of Swisserland.* In Krondal, the Hesics

. mountains of Mexico, the oscillations will be found to glaciers are described by Von Buch, as a huge, daz

amount to 2405 toises, attaining their maximum in zling, white carpet, fastened on both sides to mighty January, and their minimum in September ;8 and, rocks; and when they have reached the valley, they

although we are not acquainted with the actual extent still continue to push on, like the glaciers of the Rhone. Evra of the oscillations on the mountains of Himalaya, we Between the sixtieth and sixty-first degrees of latitude,

may infer from the observations of Captain Hodgson, according to Hagelstam, the perpetual glaciers have a that they must be considerable. The great cedar pines, breadth of 4600 feet, or nearly seven-eighths of a those gigantic sons of the snow, says he, fringe the bare mile.t

(408.) Our limits will not permit us to pursue this Causes of It may be necessary to observe, that we do not confound the

chain of inquiry in all its generality, and we must alteration in phenomenon of the perpetual snows with that of glaciers. The inse- therefore briefly remark, that the variations of tem- altitude of

perpetual rior limit of ice is determined by other causes.

perature occasioned by the ordinary changes of the + These people have an ancient usage of giving a snow-bath to those who, for the first time, pass from the less elevated plains, * An example of their terrific power may not be uninteresting. In through the zone on the declivity of the Cordilleras, which may be the year 1744, the few persons inhabiting the valleys alluded to in accidentally covered with snow; the burlesque ceremony agreeing the text, complained that they were not able to pay their taxes, with the baptism which sailors undergo, who for the first time pass because the Jis-Braeer had rushed upon their fields, and completely the Equator.

covered them. This statement was not credited, and Surveyors and
1 When Humboldt published his views of the Cordilleras, and Excisemen (Sorenscriver und Foged) were sent as Commissioners to
nis Atlas of New Spain, many regarded with wonder the designs measure the distance of the middle of Milvirsdal from the foot of the
which represented the icy regions of the Cordilleras of Quito and nearest glacier, and it was ordered that the same measurement should
Mexico. Accustomed to the snowy mountains of the Alps and take place every three years, to ascertain whether or not these
Pyrenees, and to the vicissitudes which they undergo during the glaciers were advancing. Three years after, the same Commissioners
successive seasons of the year, they transferred similar ideas to the went to repeat their measurement, and were not a little astonished to
mountains of the New World, and were surprised to find those find neither fields nor houses. The Jis- Braeer had advanced pro-
glaciers wanting, which in Europe impart so much grandeur and digiously, the inhabitants were gone, and their possessions buried
beauty to Alpine scenery. See Vues de Cordillères, pl. 5. 10. 16. under the ice. (See Thaarup's Magazin fur Stalistik, 1802.)
25. 35. 42. 51. et 61.; and Atlas de la Nouvelle Espagne, pl. 16. et In the Bibliothèque des Sciences et des Arts, Professor Pictet
17.; and Atlas Géographique de l'Amérique Méridionalle, pl. 1. informs us, that the Glacier des Bossons has lately (1818) advanced

Ś We must not confound the perpetual snows with the snows fifty feet, much to the dismay of the neighbouring villagers.
which in winter, sometimes, fall in much lower regions. This ephe- † There are many mountains in Norwegian Lapland, whose names
meral snow, says Humboldt, is never observed under the Equator at terminate in geikna, and from all of which glaciers proceed. In
12,467, or 12,795 feet; but in Mexico it is commonly seen at an Lapland, the name geikna, or jackna, is applied in the same way as
elevation of 9843 feet. Snow has been seen in the streets of Mexico the Icelandic word jockal ; the Norwegian word jisbræ; the Tyro-
at 7471 feet, and at 6159 feet, in the City of Valladolid.

lese word ferner; and the Swiss word gletcher, (glacier.)

Snows,

Latitude, or Place of Observation.

Observed Alti.
tude of Plane Mean Temper.

of Perpetual ature of lower
Snow, above the limit of Plane of
level of the Sea, Perpetual Snow.

in Feet

15747

34°70

this plane.

tions of

Meteor seasons, are not the only causes which have a tendency

Table XC.

Meteor ology. to produce alterations in the elevation of the plane of

ology. the perpetual snows. There must be some differences

1
of altitude due to the diurnal changes of temperature,
although the present condition of our knowledge will
not permit us to estimate their value. The horizontal
winds, also, which mingle the temperatures of different At the Equator ..
zones, contribute sometimes to augment the circum-

In the Temperate Zone....

8856 25.34
stances of temperature, and at other times to diminish

In the Frigid Zone, in lat. 68°—69o. 3414 21.20
it, in each case exercising some effect on the altitude of
the perpetual snows. The enormous beds of clouds
likewise, which are found sometimes to exist in the in-

(411.) The first theoretical attempt to trace the alti- First theoterval between the plains and the limits of constant

tude of the plane of the perpetual snows in different retical atsnow, cannot but be without their effects. The produc- latitudes, was also made by Bouguer. Mayer, although tempt to

estimate tion of caloric, which, says Humboldt, is the effect of occupied with the subject of terrestrial temperature

height of the extinction of light, and which diminishes with the twenty years later, having deduced, as we have before density of the superincumbent strata of air, may not, it

seen, a formula to represent the same, did not venture is true, be appreciable by our instruments; but the to trace the gradations of heat in the atmosphere, and masses of vesicular vapour, and the clouds which

to ascend to the frozen regions above. It was sufficient,

present distinct and perfect contours, and which in the indeed, for his reputation, that, occupied with the mighty tropical regions attain an elevation of 3000 toises, be subject of the lunar Tables, he was yet able to marshal come heated to a sensible degree, and emit radiant the terrestrial temperatures, and develope a law which caloric to great distances. On the other hand, at a less should approximate in some tolerable degree to that of elevation on the Eastern side of the Cordilleras of the geographical parallels. Kirwan, eager to embrace Kirwan Mexico, a thick stratum of clouds augments, during the whole question, ventured to combine the experi- combined several months, the cold of the superior regions, by in

mental observations of Bouguer with the theoretical de- the observa. tercepting the radiant caloric of the plains. Nor must ductions of Mayer, and regarded the elevation of the

Bouguer we omit the consideration, that while the directions perpetual snows in every latitude, as proportional to the with the of the great mountain chains exercise a very import- difference of the mean temperature and the constant deductions

of Mayer. ant influence on the figure of the plane of perpetual temperature of the freezing point. snows, the grouping together of mountains has, in all (412.) Professor Playfair, also, by means of Mayer's Playfair's cases, an effect on its elevation; tending to diminish formula of mean temperature, endeavoured to deduce formula for the altitude, when their summits penetrate above it. the altitude of the perpetual snows as follows. Since the same

object. Figure also (409.) We may also add, in again alluding to the that formula is represented, says he, by influenced figure of the plane of perpetual snows, that on account

T = 58 + 26 cos 2 L, by inequa- of the inequalities of temperature which exist in the and that at the limit of congelation T becomes 32, the perature of

Northern and Southern hemispheres, some varieties, equation may assume the form of Northern both in form and elevation, are due on this account.

32 = 58 + 26 cos 2 L - 0,
and South. The elevation of the perpetual snows in the parallel of
ern hemis
spheres.

Cape Horn must differ from that of Edinburgh, since provided we assign to the function 0 a proper value.
the former ranges freely over the Ocean, and tbe latter

(413.) The value of this function is necessarily de-
is subject to all the vicissitudes of temperature arising pendent on two conditions, the altitude of the point of
from the unequal radiating powers of large portions congelation, and the decrement of altitude due to the

It
may

hence
of the Continents of Europe, Asia, and America. change of a single degree of Fahrenheit.

h
Whatever circumstances, indeed, occasion diversities in be denoted by if we represent by the numerator of
the temperatures of the two hemispheres, cannot be
without their effects on the altitude of the perpetual the fraction the first of the elements alluded to, and by

the denominator the second. This assumption will, Supposition

(410.) We must now hasten to advert to another therefore, cause the preceding equation to be transof Bouguer most interesting branch of the inquiry. It had long formed into

h that temper- been believed after Bouguer, that the lower limits of ature of

32 = 58 + 26 cos 2 L the plane of perpetual snow indicated everywhere a lower limit of snows is temperature corresponding to the freezing point; but and from which we obtain constant. Humboldt has shown, in a Memoir read to the French

h = 26 A (1 + cos 2 L), Shown by Institute in 1808, and, again, in his Paper on the and which, according to Playfair, will furnish the altiHumboldt Inferior Limit of the Perpetual Snows on the Moun- tude of perpetual snow for every latitude. to be erro- tains of Himalaya, that such a supposition is contrary (414.) Professor Leslie has likewise been led to the Leslie's in

snows.

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to the truth, and that the perpetual snows do not follow consideration of this problem. Having deduced the vestigation
an isothermal plane. Their direction, indeed, follows:
less the traces of the isothernal lines of the planes, than * Playfair, in his Outlines of Natural Philosophy, assigned to the
the inflexions of the lines of equal summer. By uniting altitude of perpetual snow at the Equator 15,577 feel, as before given
many good observations, Humboldt found that at the by Kirwan, and hence deduced 294 feet for the value of a. In
lower limit of perpetual snow, the mean temperature of doing this, however, the Professor fell into an error respecting the

formula of Mayer, by assigning to the constant coefficient of the dou-
the air is as recorded in

ble latitude, the value of 27 instead of 26 ; and hence his equation for
the altitude of perpetual frost was

h=7644 +7938 cos 2 L,
iostead of the more convenient form given to it in the text.

neous.

25

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Lati tude.

Height of Plane

of Perpetual Snow in English

feet.

Lati-
tude.

Height of Plane

of Perpetual Snow in English

feet.

Lati.
tude.

Height of Plane

of Perpetual Snow in English

feet.

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Meteor. formula before alluded to for the decrement of temper- temperatures of the geographical parallels by the for- Meteorology. ature in the air, he was naturally led to that limit, which mula of Mayer, which not representing exactly the ology.

gives to it the character of congelation. The Professor distribution of terrestrial heat, must necessarily have communicated to his formula two forms, as we have some effect on the computed values for the altitude of before seen in the functions represented by (L) and the perpetual snows. It proceeds also on the suppo(M), and deduced from either the altitude of the per- sition that this plane is one of an isothermal nature, petual snows.

which, we have before remarked, has been proved by (415.) If we adopt that which we have denoted by Humboldt not to be the case. Hence the differences (M), and represent the temperature at the level of the between the results of the Table, and those recorded Ocean by t, we shall obtain the equation

from actual observation in Table LXXXIX., are con

siderable. At the Equator, the formula is only in Differences It.

defect 541 feet, but in the parallel of Mexico the differ- between the ence, according to one observation, amounts to 1066 Table and

actual obThis value of t being known for every latitude, or at feet, and according to another to 1386 feet. With one

servation. least being capable of computation by any formula of of the observations made on the Himalaya chain, there temperature, we may regard 0 as the unknown element is a surprising coincidence between the formula, and the to be determined, and hence obtain, by a simple alge- point where the Gauri river emerges from the snow; braical reduction,

but at the Nitee Ghaut, the Chárang pass, and the 0 = 7 (1 +.0004 ") - .02t....(Q),

somewhat doubtful results relating to the mountains

enclosing the dell of the Táglá river, the differences are Relatire which gives in terms of the temperature at the level of of the most surprising kind. With the observations elasticity of the sea, the relative elasticity of the air at the limit of made on the Caucasus, the theory is in defect the enorthe air at congelation. The question thus becomes reduced to the mous quantity of 2213 feet; but with the Pyrenees it is the limit of

ordinary methods of determining barometric altitudes, for the first and last time a small quantity in excess. congelation.

and on this principle the Professor computed the follow- With the Alps it is again considerably minus, and with ing Table.

the estimated range of the perpetual snows above the

Carpathian chain, it is in defect upwards of 1900 feet.
TABLE XCI.

In Sweden, admitting the observations of Hagelstam

to be correct, the difference is still greater, although a Labe's

somewhat closer approximation is obtained for FolgeTabla la

fonden, in Norway. With the snows on the mountain atitude of

of Sulitelma, given on the respectable authority of Wahperpetual 09 15207 31° 11253 62° 3365

lenberg, the difference amounts to 1512 feet ; and at I 15203 32 11018

the North Cape, where the last visible traces of the per

63 3145 2 15189 33 10778 64 2930

petual snows on land are found, the defect still amounts Y3 15167 34 10534 65 2722

to nearly 800 feet. 4 15135 35 10287

(417.) These anomalies may, however, be more clearly Graphical

66 2520 5 15095 36 10036 67 2325

discerned by means of the graphical illustration denoted illustration 6 15047 37 9781

2136

by fig. 9, in which the horizontal line E N represents the of the same. 7

interval between the Equator and the North Pole, divided
14989 38 9523 69 1953
8 14923 39 9263 70 1778

so as to correspond with the principal latitudes contained
14848

in Table LXXXIX.; and on each vertical line raised at
40 9001 71 1611
10 14764 41

the latitudes referred to, is laid off the altitude of per-
8738 72 1451
11 14672 42 8473 73 1298

petual snow. according both to theory and observation.
12 14571 43 8206

Thus, from E to B denotes the altitude of the perpetual

74 1153 13 14463 44 7939 75 1016

snows at the Equator, as indicated by the Table of
14 14345 45

Leslie, and from É to G the mean of all the Equatorial
7671 76 887
15

observations of Humboldt. A simple extension of the
14220 46 7402 77 767
16

same principle produces the curve of contrary flexure
14087 47 7133 78 656
17 13947

BCDFN, of which the one half is nearly the reverse
48 6865

552
79

of the other, for the general range of the perpetual
18 13798 49 6599 80 457
19 13642

snows according to theory ; and the irregular line
50 6334 81 371

FGHIK, that which is produced by connecting to-
20 13478 51

6070 82 294
21 13308
5808 83 226

gether the points with which actual observation has

furnished us. C is the point where theory so nearly
22 13131 53 5548 84 167
23 12946 54 5290

117

agrees with the measurement found for the Gauri 24 12755 55 5034 86 76

river, and D the solitary example of its being in excess

of the actual observations made on the Pyrenees. The 25 12557 56 4782 87 44

towering summit at H is worthy the most attentive 26 12354

4534 88 20 27 12145 58

consideration. The part of the horizontal line E A 4291 89

5

refers to the observations of Humboldt made South of 28 11930

4052 90

0

the Equator.
29 11710
3818

(418.) Although the theory is in all cases in defect
30 11484 61 3589

excepting one solitary instance, it would be unjust to

charge upon it the whole amount of the differences that (416.) With respect to the preceding Table it may have been found, since errors in the actual observations be remarked, that Professor Leslie has computed the on the perpetual snows do in all probability exist to

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52

85

Renarks.

Latitude, or Place

of Observation.

Values
of n.

Computed

Mean
Temper
ature at
Plane of
Perpetual
Snow.

Observed
Mean Tem-
perature at
Plane of
Perpetual

Snow.

Durerence.

Observed
Mean Tem-

'Altitude of
Mean Temperature of Dectement Plane of
the Earth's of Plane

ature.

Snow above
Surface of Perpetual

the level
Snow.

of the Sea.

Decrement of
Altitude in
fret, corre-
sponding to
degree of
Fahrenheit's

Scale.

of Observation.

Meteor-
some considerable amount. The remarkable circum-

TABLE XCIII.

Meteorology stance, however, that all the differences between theory

ology. and observation, excepting one, are of a negative character, is sufficient to awaken a salutary caution respect

Computed The results ing its results. That the conclusions of actual observaof observa- tion cannot in all cases be relied on, may be inferred tion cannot in all cases from an examination of the results of Table XC. By be relied on. computing the decrement of altitude corresponding to

At the Equator .... 48.74 32.76 34.70 +1994 Proof from a single degree of Fahrenheit's thermometer, for the In the Temperate

30.04 27.59 25.34 -2.25 the decre. whole range of elevation from the Earth's surface to the

Zone ... ment of plane of congelation, we shall find the results for the In the Frigid Zone altitude,

12.84 17.03 21.20 +4.17
three zones to be of a very anomalous kind. If we

in lat. 680 69o..
adopt for the mean temperatures at the surface, the
values recorded in Table XLII., and for the mean

Here the errors between the observed and computed
temperature of the lower limit of perpetual snow, those values of the mean temperature at the plane of per-
contained in Table XC., we shall obtain the following petual snow, seem to indicate that considerable ano-
results :

inalies exist in the observations, probably in the temTABLE XCII.

perate and frigid zones. It may also be remarked Inference respecting the formula last employed, that it affords by from it that its application to the principal results contained in it is not an Table LXXXIX., a confirmation of Humboldt's re

isothermal

plane. Latitude, or Place perature at lower Limit of Temper- Perpetual

mark, that the temperature of the plane of the per-
petual snows is not of an isothermal kind. It may

likewise be added, that the altitude at which the mean
At the Equa- }| 810.50 34070

temperature of the freezing point is attained in the
460.80 15748 336
tor

great range of the atmosphere, seems according to for-
In the Tem-l

mula (P) to vanish in about latitude 66° 53'; the great
57.63 25.34 32,29 8856 274
perate Zone.)

isothermal plane corresponding to 32° of temperature,
In the Frigid

appearing to meet the Earth's surface in that latitude. Zone, in lat. 29.87 | 21.20 8.67 3444 396 This conclusion has been obtained by computing the 689_69o.

altitude due to 39° by aid of the formula last quoted,

and adopting the mean temperatures recorded in Table Causes of These anomalies may again be attributed to two sources,

XLII. the ano- errors in the altitudes, or in the observed mean temper

(420.) There is another uncertainty also respecting the Probable malies.

atures of the plane of perpetual snow in the latitudes altitudes which have been assigned to the lower limits uncertainty referred to; and that it exists with much probability in of the plane of perpetual snow, which must be briefly ad- respecting the latter, may be inferred from the following considera- verted to. The perpetual snows may be said in a general altitudes of tions.

way to attain their maxima and minima of elevation at the the plane of (419.) We have before found that the formula repre- opposite seasons, when the greatest and least tempera- perpetual sented by (P) denotes, in a convenient manner, the tures for the year take place at the Earth's surface; and snow. relation between the depression of the thermometer, the periods when travellers are most likely to approach and the altitude observed; and if we suppose by way them, will not be when they are most broadly deveof subjecting the three observations in the preceding loped, but when they are approaching their mean, or,

Table to the same test, that the altitudes are correct, perhaps, their least state ; when the warmth of the Attempt to and that the question for consideration is to determine atmosphere has caused the snowy boundary to rise concompute the the mean temperature at the altitudes recorded in the siderably above the lower limit assigned to it by the mean tem

same place, let us find from the formula last quoted, minimum temperature of the year. This circumstance perature at that value of n, which represents the depresion of may afford room for supposing that the heights assigned perpetual temperature due to the elevation. By an ordinary to the lower regions of perpetual snow are above what snow. algebraical reduction, this will give

they ought to be; and that hence by applying some

correction, which the future progress of Meteorology
2 h
83
+ 83.26%

may disclose, a closer approximation may be found be-
3

tween the results of observation and the deductions of
and by adopting as successive values for h, the altitudes theory; particularly in the temperate and frigid zones,
recorded in Table XCII., we shall obtain for the values where the discrepancies from this cause may be sup
of n, the depressions recorded in the first column of the posed to be the greatest, in consequence of the greater
next Table. By subtracting these from the correspond changes that take place in the altitude of the plane of
ing mean temperatures at the surface, we shall find in perpetual frost during the successive seasons of the
each case the computed mean temperature at the altitude year;
of perpetual snow.

The whole subject is, as yet, entangled with many
difficulties, and will require much laborious research to
carry it to perfection. All the anomalies which accom-
pany its progress, must, however, be fairly stated before
such desired results can be obtained. *

n =

* In the following sections (422.) ought to be numbered (421.), and so on.

ology

means,

Meridiany.

Values of a.

Meteor

(422.) At the moment this sheet was going through we have represented in fig. 1. pl. ii. by the dotted lines, Meteorblogy. the press, a Memoiron the mean temperature of the isothermal lines being those of a continuous kind.

the air, and of the ground, in some parts of Eastern sealher- Russia, reached us, which was read before the Academy of St. Petersburgh in February 1829. M. Kuppler

On Atmospheric Vapour and its Distribution. introduces to our notice in this able paper, a new species of lines which he denominates Isogeothermal lines, and which appears likely to lead to some new and interest-bution of heat have disclosed so many interesting existing in

(424.) If the phenomena connected with the distri- Vapour ing results

. Kuppfer deduced these lines from the results, in no less a degree does the vapour with which thermotemperatures of springs, and their projections were found the atmosphere is stored. By vapour, we are to un

sphere. to deviate very widely from the isothermal lines.

derstand a very rare, light, expansible body, capable (423.) Kuppfer determined the positions of his new

like air of a reduction of volume by external pressure, system of lines as follows. He supposed a relation to and also of resisting any force which may tend to exist between the latitude and the temperature of the

compress

it. This vapour exists in every climate, ground, capable of being represented by the equation

and under every variety of temperature; in the frigid a -b sin?l=i,

atmosphere of the polar zones, as well as in the burning in which / represents the latitude, t the corresponding regions of the Equator; nor is there a particle of air untemperature, and a, b constant quantities necessary to influenced by its presence, at least in the lower atmobe determined for different meridians. Having deter- sphere, unless it be relieved from its agency by artificial mined these coefficients, he found that the observed and

This moisture, extensively as it is diffused, Owes its calculated temperatures agreed pretty well, excepting owes its origin to the waters which cover so large a por- origin to for Cumana, Teneriffe, Konigsberg, and Umeo, places tion of the globe, and which penetrating by a thousand the waters upon which local circumstances appear to impress an channels, communicate some of their humidity to the which cover

the globe. anomalous character. The meridians assumed by earthy soil; and it is to the active agency of heat, that Kuppfer, reckoned from that of Paris, are contained in the rising moisture, the result of evaporation, the the following Table, together with the corresponding laws of which we shall hereafter trace, is compelled to values of a and b in degrees of Reaumur.

distribute itself throughout the different regions of the

great aerial volume. Table XCIV.

(425.) It will readily be imagined, that to trace in Problem of all their generality the laws which regulate the dis- its distri

tribution of vapour, throughout the whole extent of bution a Values of b.

the atmosphere, perpetually changing as are all its difficult one. 0° 210.3 20°.9

conditions of density and temperature, must have long

been regarded as a capital problem in Meteorology. 20 E. 24.4 25.6

There is a wide interval, indeed, between the first rude 60 E. 22.9 27.5

conceptions of the existence of vapour in the air, and

those comparatively perfect processes, which our own 80 W. 24.0 33.7

times have disclosed, respecting the moisture of the

aerial columns; and it would be an interesting employo By a ready transformation of the preceding formula ment, did our limits permit, to trace up from its feeble into the form

beginnings that magnificent chain of discovery, which,

connected with the existence and elastic force of vapour, cos 21=1-2

has imparted so splendid a succession of benefits to Man. b

(426.) The ordinary purposes of Meteorology require Elastic Kuppfer has been enabled to calculate for each of the only a knowledge of the elastic force of vapour belong- force of preceding meridians, the particular latitudes where any ing to a comparatively small range of temperature, and vapour. given temperature prevails, and the results of which are

the latest inquiries have added but little to the accuracy contained in the next Table.

which Dalton so long ago imparted to them. Very

recently, indeed, we have seen the elastic forces pushed Table XCV.

up through the extraordinary range of twenty-four at

mospheres, by Prony, Arago, Ampère, Gerard, and Corresponding Latitude under Meridian.

Dulong; and we cannot sufficiently admire the inge

nuity and talent displayed in so laborious and hazardous 20° E. 60° E. 800 W.

an inquiry, which we ardently hope will lead to some

reaily practical means of averting the tremendous cala77° 30' 65° 52 57° 32'

mities attendant on explosions by steam.*

(427.) We have already given, in p. 333 of our Essay Its practical 5 620.12' 60 31 53 47 48 40

on Heat, the practical results of Dalton and Ure for the results ca47.20 | 48 36 43 14 40 8 elastic forces; and it affords another beautiful example pable of

being repreof the power which analysis possesses, of bringing under

sented by a 15 33.18 37 19 32 25

7

its dominion a variable force, which the early cultivators formula. 20 14.27 24 30 18 57 19 44

of Physics must have placed in almost hopeless ob

scurity, among the phenomena of Nature incapable of By allowing lines to pass through these points of

For a full account of these admirable experiments, see Annales equal temperature, we shall obtain a perfect idea of the

de Chimie, Janvier 1830, or the Edinburgh Journal of Science, July positions of some of the isogeothermal lines, which 1830, for a copious abstract of the same.

VOL. V.

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