TEMPERATURE. 



From die above obfervations it appears, that though the 

 fea at a moderate depth was cooler than at the furfaco during 

 the fummer montlis in nortlieni latitudes, yet at Hill greater 

 depths the temperature increafed, and at the depth of 260 

 fatlioms was 52° in July, when the furfjce was only 47°. 

 Now this depth being below tlie immediate cffeifls of the 

 folar rays, the temperature could only be derived from that 

 of the globe itfelf, which appears to be fufficient to preferve 

 the fea many degrees above the freezing point at the depth 

 of 300 fathoms. Indeed, the temperature of the fea near 

 the tropics, in lat. 25^ 13', at the depth of 650 fathoms, 

 appears to be the fame as the temperature of the fea in 

 kt. 68° 43', at little more than one-third of tliat depth, as 

 maybe feen by comparing the obfervationsofCapt. Ellis with 

 that of Capt. Douglas. We have hence alfo ilroiig grounds 

 for believing, that at a certain depth, the temperature of the 

 fea is permanent, and is the fame in every degree of latitude 

 from the equator to the pole, though the depth may vary at 

 which this permanent temperature would be found. 

 . The mean annual temperature of the Itandard fituation in 

 every latitude, as deduced by Mr. Kirwan from the Atlantic 

 and Pacific oceans, is given under the article Temperature of 

 the Atmosphere. But fom? exceptions to this ftandard, 

 not there noticed, deferve to be mentioned here. 



That part of the Pacific ocean which lies between N. lat. 

 52° and 66°, is only about 45 miles broad at its northern 

 extremity, and 1300 miles at its fouthern. It is, therefore, 

 reafonable to conclude with Mr. Kirwan, that its tempera- 

 ture will be confiderably influenced by the furrounding high 

 land, as well as by the many bleak iflands fcattered through 

 it. Mr. K. fuppofes, that from thefe circumftances the 

 temperature is fully four or five degrees below the ftandard. 

 Small feas furrounded by land are ufually rendered, from 

 this circumftance, at leaft in temperate and cold climates, 

 warmer in fummer and colder in winter than the ftandard 

 ocean : the gulf of Bothnia, for inftance, is ftated to be 

 generally frozen in winter, but in fummer to be fometimes 

 heated to 70°. The German ocean is above three degrees 

 colder in winter, and five degrees warmer in fummer, than 

 the Atlantic. The Mediterranean fea is, for the greater part 

 of its extent, warmer both in fummer and winter than the 

 Atlantic, which therefore flows into it. The Black fea is 

 colder than the Mediterranean, and flows into it. 



Thefe obfervations apply chiefly to the furface of the 

 ocean : from experiments that have been made it appears, 

 that at confiderable depths the temperature is much lower 

 than at the furface, and that the deeper we go, the lower it 

 becomes ; fo that fome fuppofe that, at very great depths, 

 the water always exifts in a Hate of ice. See Kirwan's 

 " Eftimate of the Temperature of different Climates;" alfo 

 his " Efl^ay on tlie Variation of the Atmofphere." 



Temperature of Springs. Thofe common fprings 

 which throw up a confiderable quantity of water during the 

 whole year, have generally a permanent temperature, or 

 nearly fo ; and this is fuppofed to repreient the mean tem- 

 perature of the earth in each latitude ; but there are other 

 fprings which have a much higher permanent temperature, 

 and fome which throw up their waters at a boiling heat. 

 The following is the permanent temperature of fome of the 

 more celebrated warm fprings in Europe. 



Fahr. 

 Matlock, - - . . 66° 



Buxton, - . . - - 82 



Briftol, - - - - 74 



Bath, - - - - j"< 



' 1 1 16 



Vichy, - - - - 120 



Vol. XXXV. 



Fahr. 

 Carlfljad, - - - - 165° 



Aix, - - - - 143 



Borfet, - - - - 132 



Bareges, - - - - 1 20 



The Gcyfers or boiling fountains in Iceland, in the Azores, 

 and in various parts of the world, have a conftant tempera- 

 ture of 212'^. Tiie fource of heat, in fome of the latter 

 fprings, is evidently fubtcrranean fire, as all thofe iflands are 

 of volcanic origin, and .are the feats of aftive volcanoes at 

 the prefent day. It is obferved of other warm fprings, that 

 they generally rife in the vicinity of volcanic orbafaltic rocks. 

 This is the cafe with the warm fprings of Matlock and 

 Buxton. Rocks of bafaltic amygdaloid extend through the 

 high peak of Derbyfhire, where thefe fprings arc fituated. 

 Rocks of bafaltic amygdaloid, having a rtill more near 

 refemblance to volcanic lava, extend from Worford bridge, 

 in Gloucefterfliire, in a direftion fouthward, and, in all pro- 

 bability, are continued under the furface to Bath and Briftol. 

 According to Humboldt, hot fprings rife from granite and 

 rocks denominated primary, in various parts of South Ame- 

 rica ; and, from the permanent high temperature of warm 

 fprings, we may infer that the fource of heat is fituated deep 

 beneath the furface, and far below thofe caufes which can 

 change the temperature. It has been contended by forrte 

 perfous, that the high temperature of warm fprings arifes 

 from the decompofition of pyritous ftrata ; but if tnis were 

 the cafe, the waters would be ftrongly impregnated with 

 fulphate of iron and other mineral matters, which is not the 

 faift ; the temperature would alio decreafe as the pyritic 

 matter became exhaufted, of which we have an analogous 

 illuftration in the faline fprings of Cheltenham and Gloucef- 

 ter. Thefe fprings rife in a deep ftratum of blue clay, called 

 lias, (fee Strata of England,) which abounds in pyrites, 

 and in animal remains ; and it is found by experience, that 

 the fahne impregnation is greatell when the wells are tirft 

 opened, and that the ftrength of the waters gradually declines ; 

 oil which account, the proprietors are under the neceflity of 

 finking frefli wells to obtain water of the requifite faline 

 ftrength. This might be expefted ; for as the water per- 

 colates through fiffures in the clay, the fahne matter in its 

 vicinity is gradually wafhed away. But if the whole bed 

 were in a itate approaching to ignition, from the decompo- 

 fition of pyrites, the faline impregnation would be con- 

 ftantly fupphed to the fprings ; for we cannot fuppofe any 

 quantity of pyritous matter to exift equal to heat a whole 

 ftratum by decompofition, without, at the fame time, gener- 

 ating fuch an abundance of faline matter as muft faturate the 

 waters which percolate through it. We are hence led to infer 

 that the fource of heat in warm fprings is firbterranean fire, 

 and as thefe fprings have not been obferved to diminifti in 

 temperature for a period of nearly two thoufand years, we 

 may further infer the great depth at which this fource of 

 heat is fituated, an inference which is warranted by the con- 

 nection which volcanoes in diftant parts of the world appear 

 to have with each other. (See Volcano.) It may be 

 aflced, if the fource of lieat in warm fprings be fubterranean 

 fire, why are they not all of the fame degree of temperature i 

 To tiiis it may be replied, that, in fome inftances, the warm 

 fprings may W intermixed with cold fprings near the fur- 

 face ; and in other inftances, after rifing to a certain height, 

 they may run in an horizontal direftion for a confiderable 

 diftance among the upper ftrata, and thus be gradually 

 cooled. The eaufe which can raife up water from vaft 

 depths, mull be fought for in the expanfive power of fteam, 

 and elaftic vapours generated by heat, which we know by 

 experience to be fully adequate to the cffeft. 



S f Temtera- 



