448 
calculated by my formula, in its complete and less perfect 
form, from the observed temperatures of a wet and dry 
thermometer. 
(Top of Sugar-loaf, April 23, 1840.) 
f= 60°S; (FS 6"2 3 = Fp ee 
t’’ (by Daniell’s hygrometer) = 47.5. 
t” (by formula f’= f’ — ‘0114 (¢ — 2’) x pt) = 468, 
t”’ (by formula f” = f’ — ‘0114 (¢— #) ) = 46°-22. 
3 =i which, in the pre- 
ceding observation, = ‘9366, the calculated dew-point comes 
out 0°58 too low. This, however, may, under ordinary 
circumstances, be considered as an extreme error; for ¢—¢ 
Pat 
30 
* Thus, by neglecting the factor Pp 
is seldom so high as 7:6, and scarcely ever so low as 
‘9366, at least in this climate.” 
May 20. 
REY. H. LLOYD, A.M., Vice-President, in the Chair. 
A paper was read by the Secretary, being a continuation 
of Mr. George J. Knox’s researches ‘‘ on the Direction and 
Mode of Propagation of the Electric Force, and on the 
Source of Electrical Development.” 
In the commencement of this paper the Author describes 
some experiments, from which he concludes that all fluids 
convey the electric force through their substance; while 
with regard to solids no regular law exists, some conveying 
the electric force through their substance, while others con- 
vey it along their surface. He next considers the source of 
electrical development, and shows that it must originate in 
