north-east, has again thoroughly clouded the sky, night
beautifully clear, no rain, and no wind during the day.

_2nd_.--A windy but clear night, succeeded by a beautiful morning, wind
as usual, north-east or thereabouts, i.e. down the river.

I have seen it mentioned somewhere, that in arid climates the only
support of vegetable life exists in the dews, which are hence, at least
in the cases alluded to, supposed to be providential adaptations to
supply certain deficiencies. But considering that dews consist of
nothing but a deposition of moisture: it follows that in very arid
climates, as there is no moisture, so there can be no dews. For the
deposition of a dew, the fist essential thing, is moisture, either in the
ground or in the air, this last may have been derived from the ground. If
neither the ground nor the air contain moisture, no dews can exist, this
is the case in Khorassan.

Throughout the whole campaign no dews were noticed, although the nights
were almost uniformly serene and calm, and the time chosen for marching,
would have certainly brought us in contact with them had they been
deposited. Dews therefore do not form in Khorassan, _with these_
_exceptions_, that wherever from the nature, and the level of the soil,
water was found very near the surface, dews were deposited; as on the
_Chummums_ or low marshy pasturages at Candahar, Cabul, etc.

But even these were trifling, the aridity of the air being too great as
compared with the small extent of Chummums, to allow the deposit of any
considerable portion of the moisture it had derived from the ground.

So that aridity, instead of being adapted to dews, is a serious obstacle
to their ever appearing. With the rarity of dew, that of hoarfrost which
is nothing but frozen dew, may be associated; nor does hoarfrost often
occur, because in Khorassan it rains in the winter too freely,
particularly in all such places whose elevation is not sufficient to
cause the formation of snow, and hence where other circumstances are
favourable for hoarfrosts, _they are too much watered_ as it
were, and seldom occur. With extreme aridity, Khorassan unites extreme
electricity, the casual friction of woollen cloths, especially those of
camels' hair being accompanied by discharges sufficiently startling. The
same thing happens when caressing dogs or horses. I could never fill the
barometer without experiencing a shock as the mercury approached the
_bottom end_ of the