In reading Dr. Huxam's "Observationes de Aere," etc., written at
Plymouth, I find by those curious and accurate remarks, which contain an
account of the weather from the year 1727 to the year 1748, inclusive,
that though there is frequent rain in that district of Devonshire, yet
the quantity falling is not great; and that some years it has been very
small: for in 1731 the rain measured only 17.266 in.; and in 1741, 20.354
in.; and again, in 1743, only 20.908 in. Places near the sea have
frequent scuds, that keep the atmosphere moist, yet do not reach far up
into the country; making thus the maritime situations appear wet, when
the rain is not considerable. In the wettest years at Plymouth the
Doctor measured only once 36 in.; and again once, viz., 1734, 37.114
in.--a quantity of rain that has twice been exceeded at Selborne in the
short period of my observations. Dr. Huxam remarks that frequent small
rains keep the air moist; while heavy ones render it more dry, by beating
down the vapours. He is also of opinion that the dingy, smoky appearance
in the sky, in very dry seasons, arises from the want of moisture
sufficient to let the light through, and render the atmosphere
transparent; because he had observed several bodies more diaphanous when
wet than dry; and did never recollect that the air had that look in rainy
seasons.
My friend, who lives just beyond the top of the down, brought his three
swivel guns to try them in my outlet, with their muzzles towards the
Hanger, supposing that the report would have had a great effect; but the
experiment did not answer his expectation. He then removed them to the
alcove on the Hanger, when the sound, rushing along the Lythe and Comb
Wood, was very grand; but it was at the hermitage that the echoes and
repercussions delighted the hearers; not only filling the Lythe with the
roar, as if all the beeches were tearing up by the roots; but, turning to
the left, they pervaded the vale above Comb Wood ponds; and after a pause
seemed to take up the crash again, and to extend round Hartley Hangers,
and to die away at last among the coppices and coverts of Ward-le-Ham. It
has been remarked before that this district is an Anathoth, a place of
responses or echoes, and therefore proper for such experiments: we may
farther add that the pauses in echoes, when they cease and yet are taken
up again, like the pauses in music, surprise the hearers, and have a fine
effect on the imagination.
The gentleman above mentioned has just fixed a barometer in his parlour
at Newton Valence. The tube was first filled here (at Selborne) twice
with care, when the mercury agreed and stood exactly with my own; but,
being filled twice again at Newton, the mercury stood, on account of the
great elevation of that house, three-tenths of an inch lower than the
barometers at this village, and so continues to do, be the weight of the
atmosphere what it may. The plate of the barometer at Newton is figured
as low as 27; because in stormy weather the mercury there will sometimes
descend below 28. We have supposed Newton House to stand two hundred
feet higher than this house: but if the rule holds good, which says that
mercury in a barometer sinks one-tenth of an inch for every hundred feet
elevation, then the Newton barometer, by standing three-tenths lower than
that of Selborne, proves that Newton House must be three hundred feet
higher than that in which I am writing, instead of two hundred.
It may not be impertinent to add that the barometers at Selborne stand
three-tenths of an inch lower than the barometers at South Lambeth:
whence we may conclude that the former place is about three hundred feet
higher than the latter; and with good reason, because the streams that
rise with us run into the Thames at Weybridge, and so to London. Of
course therefore there must be lower ground all the way from Selborne to
South Lambeth; the distance between which, all the windings and
indentings of the streams considered, cannot be less than a hundred
miles.