300 Richard Adie on the Influence of 
litmus paper, that portion within the latter zone was alka- 
line, while that within the former was neutral. 
Upon the sides of the larger vessel, and the outer sides of 
the two cylinders crystals of two different forms were de- 
posited—colourless six-sided prisms, with a vitreous lustre, and 
tabular brittle crystals also with a vitreous lustre. The for- 
mer were soluble in dilute nitric acid with effervescence, and 
proved to be cerussite (PbO, CO,) ; the latter were insoluble 
in dilute nitric acid, and proved to be anglesite (PbO, SO,). 
Experiments of a similar kind have been commenced by 
Vohl,* who uses very dilute solutions of equal density, and 
makes the diffusion take place through membrane, paper, or 
a thin plate of baked clay. B. HS P. 
On the Influence of Undulating or Hilly Ground in Check- 
ing Currents of Wind. By RicHarRD ADIE, Esq., Liver- 
pool. Communicated by the Author. 
Referring to my communication in No. 113 of this Jour- 
nal, I return to the subject in order to avail myself of the 
table of the fall of rain in the Lake District, published by Mr 
Miller at p. 88 of the same Number. Also to give the 
result of some further observations, which, although not 
directly connected with the question under discussion, have 
a collateral relation, and were suggested to me through the 
consideration of the effect of hilly ground on currents of 
wind. 
The weight of aqueous vapour which crosses a ridge of 
sea-board of 100 miles long, was stated to be 4} millions of 
tons per hour, counting the velocity of the wind at the mean 
rate ascertained at Liverpool. This weight, however, is also 
much governed by the thickness of the stratum of air in mo- 
tion, which, for the calculation, was assumed to be 100 yards. 
But in the Lake District where Mr Miller’s rain gauges are 
situated, a portion of them at elevations from 1000 to 3000 
feet above the sea-level, the hourly weight of aqueous vapour 
which crosses over a district is probably far greater. 
* Liebig’s Annalen, October 1853. 
