18 Mr. Boase on the Differencesin the Statements of (Jury, 
« goniometer of 61° 40’, which is so near to the complement of P 
on M (108° 30’) that it is impossible to doubt its being P on M 
return over the edge X. Nor can a reasonable doubt exist that 
the two specimens are identical, though differing somewhat in 
appearance. They afford similar results on the apehieeen of 
heat. W. Puituies. 
ARTICLE V. 
On the Differences in ihe Annual Statements of the Quantity of 
Rain falling in adjacent Places. By H. Boase, Esq. Treasurer 
of the Royal Cornwall Geological Society. 
(To the Editor of the Annals of Philosophy.) 
SIR, Geological Society, Penzance, June |, 1822. 
Your intelligent correspondent Mr. Hanson, noticed (Annals 
for May, p. 372), that “ the differences in the annual statements 
of rain from places near together are singular, and certainly 
require an attentive inquiry.” The tables published from time 
to time, and periodically, in the Annals of Philosophy, exhibit 
still greater “ differences” than those stated by Mr. Hanson; 
and it was in consequence of remarking such anomalies that the 
resident officers of the Cornwall Geological Society instituted, 
above 12 months ago, a course of careful observations, with a 
view to an explanation of this phenomenon. 
Suspecting that a part, if not a great part, of the differences. 
arose from the disparity of gauges or measures, our first care was 
to be accurate in that respect. Fig. 8 (Plate XIII), will show 
better than a mere verbal description, the form of the instruments 
we adopted. The upper rim, a, is of copper, one inch wide; 
the basin or funnel, 6, is of pewter, two inches deep ; the outer 
gneck or cylinder, c, is of the same material, as is also the pipe, 
d. This cylinder should so fit the neck of the bottle or receiver,. 
e, as to keep the funnel quite steady ; and the pipe has a ve 
small orifice at its lower end, and is covered by a perforated lid 
at top, in order to prevent, as much as possible, evapor‘ation. 
The diameter of the copper rim is exactly six inches, and cor- 
xectly turned in a lathe and perfectly circular. All this any 
expert brazier can accurately execute, and for the cost of 4s. ar 
5s. A common bottle does well for the receiver, but it should 
be of the capacity of not less than three pints wine measure, for 
a gauge of six inches diameter. 
No less care is requisite in having a measure accurately gra- 
duated. A cylindrical glass jar or gas receiver, f, is very con- 
venient, and easily obtained. In a guage of six inches diameter 
