August 1, 1893.] Supphmni to the ^' Trdpical AgncuUuristy 
139 
a moderate degree of moisture, even in the absence 
of rain. We are told that clay and humus are 
liygroscopic, especially the latter ; that is, that 
when they have been perfectly dried, and are 
placed in moist air, they absorb a certain amount 
of water. The true hygroscopic action is, however, 
very limited even under favourable circumstances, 
and the amount of moisture thus obtained would 
be quite insufficient for plant nutrition, save in 
the case of the small growths of some of the 
lower organisms. The condensation of moisture 
from the atmosphere may, however, become con- 
siderable when changes of temperature intervene, 
and water is deposited in the soil as dew, and 
this is undoubtedly a powerful agent in renewing 
the moisture of the surface soil. The soil being 
cooled by night radiation, the moisture of the 
atmosphere is condensed, not only upon it, but 
within it if the soil has undergone a proper till- 
age ; and the plants, which in the evening 
appeared limp are in the morning again fresh and 
vigorous. The water thus condensed at the 
surface may not in all cases be derived from the 
air ; the vapour of water rising from a moist 
subsoil may be condensed at the cold surface ; 
but for this to take place after drought has long 
continued, a soil of very open texture would be 
required. In the case of gravels, this supply 
of water vapour from below is very important. 
Torthe condensation of water from the airto be of 
really practical effect, it is of course essential that 
the air should be sufficiently moist, and this con- 
dition generally fails when a drought has long 
continued. Land in the neighbourhood of the 
sea possesses considerable advantages in this res- 
pect, and crops in such localities suffer distinctly 
less in time of drought. As already mentioned, 
the amount of condensation in a soil depends 
greatly on its being in a porous state, the result 
of good tillage. 
The amelioration brought about by atmospheric 
moisture can be looked on only as a mitigation of 
drought ; for any considerable supply of water in 
the absence of rain we must look to the stores 
already in the soil. Much depends on the 
distance of the water level below the surface ; if 
this distance is only a few feet, crops should suffer 
but little in time of drought. Where, as is 
generally the case, the water level in the soil is 
at a considerable depth, the supply of water at 
the surface must depend (1) on the power of 
raising water by capillary attraction possessed by 
the subsoil : (2) on the water-holding power of 
the soil and subsoil ; (3) on the amount of evapor- 
ation taking place at the surface. 
The height to which water can be raised by 
capillary attraction depends on the narrowness of 
the passages through which it rises ; the narrower, 
however, become the passages the slower becomes 
the rate of ascent, so that a practical limit to the 
action of capillarity is soon reached. The action 
of capillarity in bringing water to the surface 
from a considerable distance beneath is much 
smaller than is commonly supposed. When the 
surface soil is far above the water level its water- 
holding power is determined by the amount 
retained on the surface of its particles, in its 
pores, and in the finer capillary tubes ; the wider 
tubes are all empty, llunius has a far greater 
power of holding water than either clay or sand, 
being far more porous iu its nature. According 
to Schloesing, some extremely fine sands, contain- 
ing no cementing material, exceed clay in their 
power of retaining Avater. Such fine sands, 
resembling silt, constitute some of the most fertile 
soils, especially when of a good depth. Much 
may be done to increase the water-holding power 
of heavy soils by deep tillage and subsequent 
pulverising of the soil ; also by increasing the 
proportion of humus by the use of farmyard 
manure or other means. 
The next important point to be borne in mind 
is the loss of water from the soil by evaporation. 
All soils when saturated with water lose by 
evaporation at au equal rate, but when partially 
dry, evaporation proceeds more rapidly in a coarse 
soil than iu one consisting of fine particles. Here 
again the advantage of good tillage is apparent. 
The greatest amount of evaporation takes place 
when the soil is occupied by a crop in full 
vigor of growth. 
The object of the farmer in a time of drought 
is that the crop shall have the full benefit of the 
water still in the soil, and that as little as possible 
shall be lost by surface evaporation. Much may 
be done to attain this result. Ey shallow surface 
cultivation, leaving in a loose state a couple of 
inches of the surface soil, the evaporation of water 
is greatly hindered. When the soil remains solid 
any loss of water at the surface is replaced from 
beneath, and so the loss becomes continuous ; but 
after the surface soil has been stirred, it dries 
without again absorbing water from below, while 
it effectually protects the lower soil from the 
action of sun and wind. The mulching employed 
by gardeners, and the application of cocoa-nut 
fibre, are still more effective plans for preventing 
useless evaporation from the soil. 
A Veterinary authority treats of the effects of 
drought on animal health in an article in a late 
number of the North British Agricullurist. He 
states that a scant and diminishing supply of 
water, which threatens many parts of the country, 
affects in many ways the well-being and life 
alike of man and beast. As essentials for animal 
life, next after continuous supplies of fresh air, 
come frequent supplies of pure water. The bodies 
of the domestic animals contain nearly 60 per 
cent, of water, which is not only a necessary 
constituent of every tissue, but is requisite for 
digestion, absorption, and nutrition ; for the 
regulation of animal temperature ; for the solu- 
tion and washing out of waste products. From 
air passages, skin, kidneys, and bowels, fluid 
matters are almost continuously excreted, and 
the loss thus sustained must be made good by 
the ingestion of water or watery food. During 
such hot weather as has been recently experienced, 
the skin secretions are greatly augmented, neces- 
sitating increased recuperation of fluid matters. 
Horses at work during hot summer weather, and 
living on mixed diet, will take daily 15 to 2o 
gallons of water, while cattle will drink even 
more ; and sheep, although popularly believed to 
be independent of water, when the air and food 
are dry, consume 2 or 3 gallons daily. 
A restricted water supply seriously interferes 
with thriving. The thirsty animal will not eat, 
no matter how tempting the food may be. So 
long as strength remains, it moves restlessly 
about ; the mouth and throat are drj-, and t he 
tongue usually swollen and protruded ; febrile 
