GLEANINGS 
IN 
SCIENCE. 
No. 4.— April, 1829. 
I . — On the Irrigation of Land in India. 
To the most careless observer, the method employed by the natives of Hindustan 
to procure such a supply of water, ns is not afforded by the season, or rather, 
which the intense heat of the climate, and the exsuccous nature of the soil demands, 
in an abundance that would be, not only useless, but hurtful, in many other countries 
remote from the tropics, must have suggested very naturally the reflection, thatthe 
labour so applied would constitute a very considerable proportion of the cost of the 
production of most of the land in cultivation ; and that a less expensive mode of com- 
manding: such a benefit, might advantageously be borrowed from the practice that 
obtains in other parts of the world. 
Water, and those vegetable debris, in the attenuation or extreme division to which 
the latter are subjected by the action of the sun, and of spontaneous decomposition, 
seem to be the chief pabula of plants. 
Moisture and a certain degree of heat are alone sufficient, in many instances, to 
elicit rapid vegetation in a small way : while, on a more extended scale, the means 
of procuring stability, to enable the young plant to withstand the action of the wind 
and rain, are absolutely requisite: and the mechanical aid of pulverulent mineral 
matter becomes indispensably necessary, to enable the radical filaments to embrace 
the disintegrated particles of such matter, as is destined to favour alike the future 
development of the tender stem, and to maintain it by its mechanical properties in 
an erect position so as to become the intermedium of its subsequent subsistence and 
nourishment. 
Soil, heat, and moisture, as well as the remains of former vegetation seem, then, 
to be necessary to vigorous and abundant production. The produce is generally found 
to be dependant upon the nature of the soil, as it regards the quality, as well as the 
quantity of the production. The degree of heat and its duration ; the abundance, or 
deficiency of the moisture ; the extent of the supply of vegetable exuvim, aided by the 
peculiar nature of the mineral substances fouud on the surface of the earth, affect 
very materially the quality and quantity of products, whether of indigenous, or of 
exotic growth, repel one kind and naturalize another, without exciting more than 
the natural curiosity of man to observe the wonders of creation, or without elicit- 
ing a greater power of intellect, than the ability to record the facts, and to reason 
badly respecting them*. 
But, of all the advantages most favourable to abundant vegetable production, the 
constant presence of moisture, even up to the period of fructuation, is one so univer- 
sally felt and acknowledged, as to be considered the sine qua non of vegetationf. 
* Some modern author has said, “ Man is a reasoning, but most often an irra- 
tional animal.” Go to science, and ask her if the blunders of what the philosophers 
term, par excellence, “ the exact sciences” are not the greatest errors that were ever 
the offspring of genius. 
t Solar light is always known to be necessary to vigorous, as artificial light causes 
sickly vegetation. Electricity, which may account for many phenomena in the ani- 
mal world not much noticed, is well known to affect the vegetable organization ; and 
some experiments may be exhibited to demonstrate the mechanical effect of vegetation, 
the resuit of rapid development and growth produced by the agency of the electric 
fluid, by means of the intermedia or conductors, fluid and solid, surrounding the 
