POLES OF GREATEST COLD. 43 



lowest temperature that, as far as we know, has as yet been 

 observed on the earth, is probably that noted by Neveroff, at 

 Jakutsk, (62 2' lat.) on the 21st of January, 1838. ^e in- 

 struments used in this observation were compared with his own 

 by MiddendorfF, whose operations were always conducted with 

 extreme exactitude. Neveroff found the temperature on the 

 day above named to be 76 (or 48 Reaum.). 



Among the many grounds of uncertainty in obtaining a nume- 

 rical result for the thermal condition of the regions of space, 

 must be reckoned that of our inability at present to ascertain 

 the mean of the temperatures of the poles of greatest cold of the 

 two hemispheres, owing to our insufficient acquaintance with 

 the meteorology of the antarctic pole, from which the mean 

 annual temperature must be determined. I attach but little 



pour 1834, p. 192; also Saigey, Physique du Globe, 1832, 

 pp. 60-76. Swanberg found, from considerations on re- 

 fraction, that the temperature of the regions of space was 

 58-5. Berzelius, Jahresbericht fur 1830, s. 54. Arago, 

 from polar observations, fixed it at 70; and Pectet at 76. 

 Saigey, by calculating the decrease of heat in the atmosphere, 

 from 367 observations made by myself in the chain of the 

 Andes and in Mexico, found it 85; and from thennome- 

 trical measurements made at Mont Blanc, and during the 

 aeronautic ascent of Gay-Lussac 107*2. Sir John Herschel 

 (Edinburgh Review, vol. 87, 1848, p. 223) gives it at 132. 

 We feel considerable surprise, and have our faith in the cor- 

 rectness of the methods hitherto adopted somewhat shaken, 

 when we find that Poisson, notwithstanding that the mean 

 temperature of Melville Island (74 47' N. Lat.) is 1 66', 

 gives the mean temperature of the regions of space at only 

 8'6, having obtained his data from purely theoretical pre- 

 mises, according to which the regions of space are warmer 

 than the outer limits of the atmosphere (see the work already 

 referred to, 227, p. 520) ; while Pouillet states it, from 

 actinometric experiments, to be as low as 223'6. See 

 Comptes rendus de I 'Academic des Sciences, torn. vii. 1838, 

 pp. 2 5-6o 



