436 JOURNAL OF THE PLYMOUTH INSTITUTION. 
cent. from the north-west quadrant, and 8°76 per cent. calms. The 
winds with a westerly tendency in them were 52°16 per cent., and 
those with an easterly tendency were 39°08; this gives four days 
of westerly winds to three days easterly ones. The strongest winds 
begin to blow from south-south-east to south, increasing in violence 
as they veer, the extreme being reached when about west-south- 
west, and gradually dying away as they approach north-west. This 
phenomena I have explained in a former paper, by showing that 
the centres of nearly all cyclones pass us to the northward ; but 
when it happens that the centre passes us to the southward the 
greatest violence is experienced from the south-east. This was the 
case in the celebrated Torbay gale, on 11th January, 1866, when 
seventy-five vessels were lost in Torbay alone, and about four 
hundred became tutal wrecks on our coasts. 
THUNDER-STORMS.— Atmospheric electricity is derived from several 
sources. Among them we may mention friction, evaporation, 
growing vegetation, and combustion. Every known substance will 
produce electricity by friction, and can be classified in order of 
power to produce that energy. It has been shown over and over 
again that substances of precisely the same kind and temperature 
when rubbed together cause no electrical action ; but only produce 
a molecular change by heating one portion and cooling the other ; 
then friction will at once evolve electricity. Air charged with 
moisture rubbing against dry air, Sir William Armstrong has proved, 
produces the energy spoken of; and much more is produced when 
the air is agitated, as in winds, and rubbed against the ground and 
against foliage. In experimental electricity friction of unlike sub- 
stances is generally resorted to for the production of that force, as 
of glass against the amalgam laid on the rubber; so water, as in 
running rivers and on our sea shores from the action of the tides 
or storms, is constantly agitated, and hence, by the friction thus 
produced, a great quantity of electricity is evolved. The second 
source I have chosen is evaporation. Pouillet showed that evapo- 
ration from chemically pure water gave to the vapour arising from 
it no electricity ; but if he dissolved either alkalies or salts in the 
water, the vapour gave positive electricity ; and if acid were added 
instead, then negative electricity was given off with the vapour, 
the vessel which contained the water in either case becoming 
charged with electricity of an opposite character. Now all the 
