REPORT ON METEOROLOGY, 
219 
whether on insulated points or in balloons, have been directly 
compared with those close to the massive heating surface of the 
earth, the radiation of heat from which probably exerts far 
more influence in producing a decrease of temperature in the 
very lowest strata of the atmosphere, than the general law 
which is sought for, and which is usually alone considered. 
The true law of decrease of temperature, such as it would be 
if the earth was removed , must be sought for probably by suc¬ 
cessive stages of balloon observation*, commencing at a con¬ 
siderable height above the surface ; or else we must find the 
means of estimating accurately the calorific influence of the 
earth by radiation and conduction. There cannot be a ques¬ 
tion that in the lowest strata the diminution of temperature 
appears much greater than at higher elevations, if the observa¬ 
tions be not made on a naturally inclined surface of soil, but at 
two stations, one nearly vertically above the other f. 
In order that the terrestrial influence may be as much equa¬ 
lized as possible, observations on the mean temperature of 
table-lands at considerable elevations, (but not covered with 
perpetual snow, which introduces a new element,) are perhaps 
the most satisfactory. And hence the reason that Humboldt’s 
equatorial observations are by far the best that we possess J. 
Humboldt’s general result gives 121 toises of ascent fora dimi¬ 
nution of 1° R. The admirable comparative observations at 
Geneva and St. Bernard, give a surprisingly near approach to 
this, the difference of mean temperature of the stations being 
8 0, 64 R. for 1069 toises: this gives 123^ for 1° B* or 352 feet 
for l°Fahr. This probably is the most correct mean result which 
we can adopt. The influence of the seasons is very considera¬ 
ble, as the following results of M. Guerin at Yentoux near Avi¬ 
gnon, lately published, prove §. 
Summer, 80 toises for 1° R., or 156 metres for 1° cent. 
Winter, 100 --or 195-- 
Some good observations made in summer upon the Rigi by 
M. Eschmann of Zurich, give 97 toises of ascent for 1° R. || 
I have succeeded in establishing, in latitude 56°, a system of ob¬ 
servation on this interesting point, from which I hope in due 
time to be able to obtain the most important results. 
* A few observations with balloons have been published by Lord Minto 
( Edinburgh Journal of Science ) : it will be necessary however to carry them 
on upon a much more extended scale, before any general conclusions can be 
attained. 
f See some observations, remarkably confirmatory of this view, by Sir Thomas 
Brisbane, (made in New South Wales,) in the Edinburgh Journal of Science. 
X Obsej-vations Astronomiques, 4to, i. 128. 
§ Annales de Chimie , xlii. 428. || Bibliolheque Universelle , 1827. 
