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VIEW, of a course of observations on the temperature of the ground at various depths.

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1815.

ON THE TEMPERATURE OF THE

GROUND

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2 Feet.

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In a former Number we gave some account, from Professor Leslie's paper May 18

520 on Climate, of the curious experi

51 ments which had been instituted at June 1 Raith, on the temperature of the

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20 ground at various depths, with the

25

54 view of illustrating the progress of

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55 the sun's heat, from the surface to

July wards the centre of the earth. Thermometers, we saw, with long stems, had been sunk to various depths, and

5656 the temperatures which they indicat 13 58 ed had been observed from time to

55 time. The register of these observa

27 57 56 tions we exhibited in the form of Aug. 10

55 curve lines, and we endeavoured to Sept.

56

.12 55 54 point out some of the conclusions

54 03 which might be drawn from it. It

23 53 was remarked how curiously each of

28 52 52 the thermometers, even to the small

Oct.

50 depth of eight feet, contracted its

18 range of heat throughout the year,

24 48 the deepest never rising so high in

28 46 48 summer, nor falling so low in winter,

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47 as any of those nearer the surface. Nov. 1 45 47 We noticed the slow progress of the

44 46 heat downwards, as it was indicated

42 45 by the effect of the depth in retarding

15 40

24 38 the thermometer's arrival at its maxi

30 mum and minimum, the extreme

Dec. ] 38 41 heat of July, and the extreme cold of

10 37 January, never in the least affecting the

20136 38 eight feet deep thermometer till the

301 33 37 months of October and March, so that the intervening three months must

1816. have been spent in travelling over this very

inconsiderable space. We pointed out also the curious circumstance of the thermometers, however they

Jan.

33° 37 might differ atother times,-of their

121

36 all agreeing with each other at two

28 stated periods of the year, and we en Feb. 1 33 deavoured to explain the reason of 12 34 these remarkable coincidences. In

27 35 short, it seemed impossible to devise Marchi 35 36 a simpler, more striking, or more ac

101

37 curate method than the observation of 21

371

35 such thermometers for exhibiting the April

12 36 singular movements of heat through the interior and near the surface of

17 364

37 the earth. T'he following is a more

30 39 complete copy, which we have now

May 39 received, of the above register, with

4 its continuation down to the present

42 year, forming altogether a course of

44 nearly four years' observation.

18 40

47 45 26 48 46 31 49 48

36

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1816.

1818.

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1 Foot.

2 Feet.

4 Feet. 8 Feet,

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1819.

showed, to the inconstancy of thesupply of heat, joined to the constant tendency of this fluid to diffuse itself equally'

among bodies—to move from the hoifeb. 10 370 38° 39° 44° ter to the colder, till a uniform tem38 31

43

perature is spread throughout, so that, 35

if the supply is at any time much ens March 8

43

feebled, as in winter, the accumula151 41

43,

tion of the preceding summer returns

to make up the deficiency. When The observations of 1818 are en- the sun, therefore, in spring gives rise tirely conformable to those of the pre at the surface of the earth to a conticeding years, and illustrate, in a si- nued flow of heat downwards, this is milar in ınner, all the above appear- met by an opposite current flowing ances; but, to show more clearly the upwards from the supply of the prepeculiar effect of each year, compared ceding year; their joint effect soon prowith the others, we have combined duces an equilibrium throughout the the whole series into one plate, (see mass, and this equilibrium takes place, Plate.) The dark waving line which according to the above observations, occupies nearly the whole compass of about the months of April or May, the plate represents the gradation of when the thermometers, from the prethe thermometer which was sunk one dominating influence of spring, are all foot in the ground, and the other somewhat below the inean temperalines, as explained in the plate itself. ture of the place. That these oppoIt is remarkable in these years how site motions of the fluid of heat near greatly all the lines, but especially the surface of the earth really take those of the deeper thermometers, – place there can be no doubt, and the how much more they sink below than variations of these thermometers place rise above the line of the mean tempe- it in a very striking point of view. rature; and this shows, in a striking In Decenı ber 1815 the thermometer manner, the low mean temperature of stood as follows: these years, not even excepting 1818, of which the summer was so very hot.

Dec. 1.
390 410

450 470 It is not improbable, therefore, that, in

10. 37 40 the present year, the lines will rise conderably above that of the mean tem

20.

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29. 33 37 41 415 perature, froin the warmth of the preceding summer, the mildness of the Here the ground was evidently warmwinter, and perhaps also on account

er in proportion to the depth ; and, of the additional supply which a se

as all the thermometers were also on ries of cold years naturally draws up the decline, it is obvious that the heat from the great reservoir below. The fluctuations to which the thermo- surface; and nothing, therefore, can

was flowing from the deepest to the meters are occasionally subject oc

show more clearly the reality of the cur, it will be seen, mostly at the ex

current which the coldness of the at. tremes either of winter or summer; mosphere was thus raising up from and this is what might be expected, below. In January 1810 they stood for, in the intervals between their

as follows: change of direction, before they have begun decidedly to rise on the one hand, or fall on the other, the least Jan. 33 370 410 circumstance, anál, therefore, the or 12.

40 43 dinary fluctuations of the climate, is 28. 33 36 39 fully sufficient to turn the balance. Feb. 12. 34 36

42 Accordingly, after a few oscillations

27.

36 39 42 about the middle of summer or of Mar. 10. 35 37 40 42 winter, the lines then hold a pretty 2.

371 40 43 steady course from the one extreme to the other. In regard to the coinci- On the 1st January, then, the one dence in our climate of all the lines foot thermometer became stationary, at the beginning and end of summer, and continued so till February 12, this must be ascribed, as we formerly when it began to rise. On the 12th

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January the two feet thermometer be- consequence, therefore, we shoull came stationary, and continued so till think, that experiments of a similar March 10, when it also began to rise. kind be made in different latitudes On the 28th January the four feet one and in different situations. The cirbecame stationary, and on March 10 cumstance of the thermometers all cobegan to rise; and, lastly, the eight inciding at the beginning and end of feet thermometer became stationary summer, may be of great use on many on January 28, and on March 21 be occasions, in approximating with exgan to rise. Here, therefore, we trace pedition to the mean temperatures of clearly the beginning, the gradual places, and, therefore, at the same progress, and the growing intensity time, to their respective elevations of the stream of heat, which the now above the level of the sea. But the increasing influence of the sun had period of these coincidences will unbegun to send downwards from the doubtedly vary in different latitudes, surface; a uniform temperaturespreads and it would be interesting, therefore, through the mass about the middle of to know the extent of the variation. May, and shortly afterwards the deep- An approximation to the relative est thermometer, formerly the hottest, height of places might also be obtainbecomes the coldest, and the arrange- ed in a manner somewhat different, ment of the heat of all the three is and which might often prove useful exactly reversed, as they stood on May to the traveller, in case a more exact 26

method were beyond his reach. So

slowly, it appears, does the heat and 48° 46° 410 440 cold penetrate into the ground, that All the thermometers now continued the vicissitudes of day and night are rising till the end of suinmer, when the quite insensible at the depth of 1 foot. interinediate ones became the highest, depth, will remain several days, and

A thermometer, even at this small and in a short time they all coincided, often 'whole weeks together, at the so that the extreme heat of summer, as it penetrated below the surface,

same degree of heat. It is obvious, secmed thus also partly to return—the then, that by thus observing the temwave of heat in its progress seemed perature of the ground at the bottom gradually, at the same time, to sub- and the top of a mountain, a pretty side, and to spread its influence equally correct idea might be formed of its over the superficial stratum of the height, even though several days ground.

Thus, in July 1817, the should elapse between the observa. thermometer stood as follows :

and this method was often practised by the celebrated Saussure.

It would be important, therefore, to July 1. 56° 54° 50° 48°

obtain observations of this kind on 10. 56 56 52 50

heights already known, in order to 19. 54 55 52 50

discover, by actual experiment, how Aug. 2. 54 52 50

far they might in other cases be trust16. 53 54 52 50

ed. It may be remarked, indeed, in 29. 52 53 52 50

general, that observations on the temSep. 10. 53

52 51

perature of the ground are, in most Here the decline of the first therino- cases, far more valuable than those meter, the extreme heat of the inter

on the temperature of air, of which medliate ones, and the gradual ap- such numbers have been made to proach of them all to an equality, are but little purpose. The former being apparent; and, if the thermometers more exempt from temporary vicishad been deeper, the dispersion of the situdes, give us more expeditioussummier's heat, as it descended, would ly the medium of all. Collecting and no doubt have been still more dis- retaining the variable impressions of tinctly exhibited.

heat, the earth shows at once the total Such, in our climate at least, is the sum of the whole ; while the air being slow and irregular, but, on the whole, subject to every the slightest inequathe steady progress of the sun's heat lity, the observations on its temperatowards the interior of the earth, and ture require to be made at regular insuch are the curious and interesting tervals, and for a great length of time, facts exhibited even by this single re before any information of consequence gister of observations. It is of great can be drawn from them. This con

tions ;

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