190 
naturalists’ calendar. 
Cause of sound emitted by Cychrus rostratus. —Among the compara¬ 
tively small number of insects which have the power of emitting voluntary sounds, 
Cychrus rostratus has long been known. Tho insect when disturbed or alarmed, 
utters a low, angry, hissing sound, distinctly audible at some distance. On the 
inner edges of the indexed margins of the elytra, are two small grooves extend¬ 
ing from near the base, to within a line or two of the apex, where they rather 
suddenly expand. The lateral edges of the plates, are, when at rest, lodged 
in these groves; and it is by their friction, particularly of the last segment but 
one, which works in the widest part of the grooves) that the sound is produced. 
An imitation of it might be made by rubbing the edge of a piece of stiff paper 
in the channel, f 
Meteorology. —Dew appears only on calm and clear nights. It is never 
seen in nights both cloudy and windy ; and if in the course of the night, the wea¬ 
ther from being serene should become dark and stormy, dew which had been de¬ 
posited will disappear. A clear morning following a cloudy night, determines a 
plentiful deposition of the retained vapour. When warmth of atmosphere is 
compatable with clearness, as is the case in southern latitudes, though seldom in 
our own country, the dew becomes much more copious, because the air contains 
much more moisture. Dew continues to form with increased copiousness as the 
night advances, from the increased refrigeration of the ground. J 
Velocity of Light. —The velocity of the particles of light is truly astonish- 
ishing, amounting to nearly two hundred thousand miles in a second of time, 
which is nearly a million times greater than the velocity of a cannon ball. It 
has been found by repeated experiments, that when the earth is exactly between 
Jupiter and the Sun, his satellites are seen eclipsed about 85 - minutes sooner 
than they could be according to the tables; but when the earth is nearly in the 
opposite point of its orbit, these eclipsis happen about 85 minutes later than the 
tables predict them. Hence then it is certain, that the motion of light is not in¬ 
stantaneous, but that it takes up about sixteen minutes and a half, to pass 
over a space equal to the diameter of the earth’s orbit, which is at least 190 mil¬ 
lions of miles in length, or at the rate of nearly 200,000 miles per second.|| 
Sunshine. —The quantity of Sunshine during February, is as follow-s : 
Average Daily. 
53 min. 2 sec. 
1833 
Morning 
Afternoon 
Total 
February. 
11 hours 
13 h. 45 min. 
24 h. 45 min 
f Entomological Magazine. * J Domestie Gard. Manual. || Huttons Direc. 
