The uncertainty of the indigo crop has been already noticed, and is, indeed, as proverbial as that from the hop plant in England.  In Bengal the crop is particularly subject to be destroyed by the annual inundation of the river, if it occurs earlier than usual.  A storm of wind, accompanied by rain and hail, as completely ruins the crop as if devoured by the locust; neither from this latter scourge is the crop exempt.

This proneness to injury extends throughout its growth.  The seedlings are liable to be destroyed by an insect closely resembling the turnip-fly, as well as by the frog.  Caterpillars feed upon the leaves of older plants, and the white ant destroys them by consuming their roots.  To these destructive visitations are to be added the more than ordinary liability of the plant to injury, not merely from atmospheric commotions, but even from apparently less inimical visitations.  Thus not only do storms of wind, heavy rains, and hail, destroy the indigo planter’s prospects, but even sunshine, if it pours out fervently after showers of rain, is apt, as it is properly termed, to scorch the plants; and if it occurs during the first month of their growth, is most injurious to their future advance.  The reason of this effect appears to be the violent change from a state of imbibing to a rapid transpiration of moisture.  No human invention or foresight can preserve the crop from the atmospheric visitations.  To destroy and drive away the little coleopterous insects which attack the seedlings, it would be a successful method to spread dry grass, &c., over the surface intended to be cultivated, and to burn the litter immediately before the sowing.  The heat and smoke produced has been found perfectly efficacious against the turnip-fly in England.  To destroy the caterpillar, slacked lime dusted over the leaves, while the dew is upon them, is an effectual application.  The white ants may be driven away or destroyed by frequent hoeings, which is the best preventive of the scorching, for hoeing preserves the soil in an equable and fitting state of moisture.

The great supply of seed for Bengal cultivation is obtained from the western provinces, and forms an article of trade of no inconsiderable magnitude.  The stubble in the low lands of Bengal is generally submerged before it has time to throw out fresh shoots, on which the blossom and subsequent seed-pod are formed.  There are, however, some high tracts reserved for that purpose, and on these the plant is found well in flower in September, and the seed fit to gather in November or early in December.

Two methods are pursued to extract the indigo from the plant; the first effects it by fermentation of the fresh leaves and stems; the second, by maceration of the dried leaves; the latter process being most advantageous.  They are thus described by Dr. Ure, in his “Dictionary of Arts and Manufactures:”—­