1879.] H. F. Blanford—Rainfall Frequency at Culcutta. Al 
Tegmina obscurely and finely punctured; wings dark fuscous with the nervures 
black. Hind tibize with a small spine towards apex. 
. Long, ex. tegm. 17 mill. Exp. tegm, 465 mill. 
Greatest long. pronot. 74 mill. Exp. lat. ang. pronot. 11 mill. 
Habitat, Taoo, Tenasserim, Alt. 3—5000 ft. 
EXPLANATION OF Puate II. 
Sminthus marginellus, Dist. 
Platypleura insignis, Dist. 
Huechys thoracica, Dist. 
Cryptotympana recta, Walk. 
Cosmoscarta tricolor, St. F. and S. var. 
rp masont, Dist. 
arr WN FE 
oe en ete sy Ie 
IV.—On the Diurnal Variation of Rainfall Frequency at Caleutta.—By 
Henry F. Buanrorp, F. G. S., F. Z. S., F. M. 8S. 
(With Plate ITI.) 
[The greater part of the following paper was written some months 
since in France, and laid before the Society at its meeting in November 
1878. In the original paper, the registers of only six years were discussed ; 
but inasmuch as those for twenty years are available in the Meteorological 
Office, on my return to India, with the permission of the Council, 
I have withdrawn and recast the paper, including in the data the whole of 
the existing registers. As might have been anticipated, the inclusion of a 
period more than three times as long as that originally treated of, has had 
the result of clearing away some irregularities, and of bringing out more 
distinctly the true character of the variation ; some of the minor features of 
which were but doubtfully indicated in the original restricted table ; while 
the more prominent features have been confirmed and emphasised. With 
a view to their more ready appreciation, a plate has been added, which 
will enable the reader to compare the diurnal variation of rain frequency 
at different seasons, with the normal diurnal variations of pressure, tempera- 
ture, relative humidity and vapour tension at Calcutta. H. F. B.] 
The tables here summarised are based on the hourly observations re- 
corded at the Surveyor General’s Office from August 1856, to March 1877* ; 
during the greater part of the period on the autographic traces of an Osler’s 
anemometer. The form of the reduction does not show the quantity of the 
rainfall, but only the fact of its occurrence at the several hours specified ; 
in other words, its comparative frequency ; and it is possible that the two 
kinds of variation may not strictly coincide. The traces in question have 
not yet been reduced for quantity, otherwise than for the total diurnal fall ; 
but the laws of diurnal variation in point of frequency are so salient and 
decided, that it is hardly likely that any conclusions to which they may lead, 
* As published in the Society’s Journal, 
6 
