SUPPLEMENTARY REPORT ON METEOROLOGY. 81 
117. We have no reason to admit any sensible change in the 
mean temperature of the superficial part of the globe; at least 
we are rather disposed to attribute the manifest elevation of 
temperature observed during twenty years, in the observations in 
the caverns under the Observatory at Paris, to some permanent 
alteration in the instrument than to a change of temperature of 
the earth, a point which we hope the French astronomers will 
take pains to ascertain. The observations from 1817 to 1835 
being divided into four series, give the following results :— 
FI+7S0 11°°801 11°°857 E950" 
118. The mean of 352 observations is 11°834 ; the mean tem- 
perature of the air at Paris is 10°822+; the difference is to 
be attributed to the increase of terrestrial heat for 28 metres 
of descent. 
119. Observations on borings, and overflowing or Artesian 
wells, have been perhaps more unexceptionable of late years 
than at any former period. We shall give such indications as 
to record the chief facts observed. Amongst the best obser- 
vations are those made by MM. De la Rive and Marcet in a 
boring near Geneva}, under the most unexceptionable circum- 
stances, which agree extremely well in indicating a uniform 
increase of heat at the rate of 1° cent. for 32°55 metres of de- 
scent, or 59 feet for 1° Fahr. The whole depth was 255 metres. 
120. A list of Artesian wells and their temperatures has been 
given by M. Arago, in the Annuaire for 1835; and by Pois- 
son, on the same authority, in his Theory of Heat§; whence 
he has deduced: (from fifteen Artesian wells in France, all above 
20 metres deep) an increase of 1° cent. for 25°46 metres of 
descent (46 feet for 1° Fahr.). There appears in these, as well 
as the Geneva and Paris observations, a remarkable coincidence 
between the superficial ground-temperature and the observed 
air-temperature 
121. From the comparison of a number of observations, M. 
Kupffer J deduces an increase of 25°37 metres for 1° Reaumur, 
or 20°30 m. for 1° cent., or 37 feet for 1° Fahr. 
122. A well at Magdeburg gives 1° Reaumur for 100 feet, 
or 44 feet for 1° Fahr.**, according to Professor Magnus, the 
inventor of an improved thermometer for such observations. 
* Poisson, Théorie de la Chaleur, p. 414. + Ibid, p. 467. 
t Mém. dela Soc. de Phys. de Généve, tom. vi. § P. 420. 
|| It is by no means necessary to infer, however, that this is a general fact. 
Prof. Reich’s observations, for example, at Freiberg, indicate an excess of 1° c. 
in the earth-temperature above the air-temperature. Beob. iiber die Temp. des 
Gesteins, &c., p. 134. 
§| Poggendorff, xxxii. 284. ** Thbid., xl. 189. See also xxxviii. 593. 
VOL. Ix. 1840. G 
