SUPPLEMENTARY REPORT ON METEOROLOGY. 101 
tended the theory ; which was reduced to practice by Auguste 
and Bohnenberger, who determined the constant with accuracy. 
English observers have done little more than confirm the con- 
clusions of our industrious Germanic neighbours ; nevertheless, 
the experiments of Apjohn and Prinsep must ever be considered 
as conclusively settling the value of the co-efficient near the 
one extremity of the scale, as those of Kamtz have done for 
the other. 
188. Of the papers of Dr. Hudson in the Philosophical Maga- 
zine*, and of Mr. Meikle, and of an anonymous author, in the 
Edinburgh New Philosophical Journalt, it is not necessary for 
me to speak, on the grounds just stated. The experiments of 
the latter have been compared with theory by Dr. Apjohn. 
B. On the Distribution of Vapour in the Atmosphere. 
189. Now that we have got asimple and intelligible hygrome- 
ter, we may hope to know more than we yet do respecting the 
distribution of vapour in the atmosphere. Accurate experiments 
are at present extremely rare; a few of the most interesting 
have been obtained by M. Kamtz. The greatest dryness he 
has observed was on the 28th September, 1832, on the summit 
of the Faulhorn, the barometer 247°4 French lines. At 9 a.m. 
the temperature of the air was 6°9 R., the moist thermometer 
fell to 0°-1 R. The computed dryness is 9 per cent. of satura- 
tiont. Clouds he has always found to be perfectly damp when 
fully immersed in them, confirming the result of Saussure, 
which has been called in question §. 
190. It has commonly been supposed that dryness increases 
as we ascend; yet it is also certain, that at a certain elevation 
clouds are more common than at any other. Accordingly, 
Kamtz finds that, whilst in dry weather the higher regions are 
drier than below, in damp weather the reverse is the case; he 
finds that, if we consider the absolute elasticity of vapour at a 
given place, there are two maxima and two minima daily; but 
if we consider the relative humidity, or proportion existing to 
the capacity of saturation, there remains but a single maximum 
of dampness at 4—5 a.m. (in June), and one minimum at 
2 P.M, 
191. The absolute quantity of moisture existing in the air is 
greatest at the equator, and diminishes towards the poles. M. 
Kamtz, from the experiments of Beechey and others, gives the 
following formula|| for the North Atlantic :— 
* Phil. Mag., 3rd Series, vii. viii. ix. t+ xv. 273; xvii. 98. 330. 
t Poggendorff, xxx. 71. § Poggendorff, xxx. p, 53, 
|| Poggendorff, xxx. 59. 
