It often happens when digging wells in sandy watercourses, that a little water is found, and that below it is a stratum of clay. Now if the digging be continued deeper, in hopes of more water, the result is often most unfortunate; for the clay stratum may prove extremely thin, in which case the digging will pierce it: then the water that had been seen will drain rapidly and wholly away, to the utter discomfiture of the traveller.
Kerkari.--I am indebted to correspondents for an account of a method employed in the plains of the Sikhim Himalaya, and in Assam, where it is called a "Kerkari," also in lower Bengal, for digging deep holes. The natives take a freshly cut bamboo, say three inches in diameter: they cut it just above one of the knots, and then split the wood as far as to the next joint, in about a dozen places, and point the pieces somewhat. The other end of the instrument should be cut slantingly, to thrust into the earth, and its other end is afterwards worked vertically with both hands.
The soft soil is thus forced into the hollow of the bamboo, and spreads out its blades, as is intended to be shown in the figure. The bamboo is next withdrawn and the plug of earth is shaken out: it is then reintroduced and worked up and down as before. It is usual to drive a stake in the ground to act as a toothed comb, to comb out the plug of earth. Mr. Peal writes from Assam:--"I have just had 4 holes dug in the course of ordinary work, in hard earth. Two men dug the holes in 1 1/2 hour; they were 3 feet 6 inches deep and 6 inches in diameter. I weighed the clay raised at each stroke. In 4 consecutive strokes the weights were 1 1/4 lbs., 1 3/4 lbs., 1 3/4 lbs., 2 lbs. Another trial gave 7 lbs. lifted, after 5 or 6 strokes." According to the above data, an Assamese workman makes a hole, 1 foot deep and 6 inches in diameter in 6 minutes. Holes 10 feet deep and 6 inches wide can be made, as I am informed, by this contrivance.
Protecting Wells.--The following extract from Bishop Heber, though hardly within the scope of the 'Art of Travel,' is very suggestive. "The wells of this country (Bhurtpoor, India), some of which are very deep, are made in a singular manner. They build a tower of masonry of the diameter required, and 20 or 30 feet high from the surface of the ground. This they allow to stand a year or more, till its masonry is rendered firm and compact by time; then they gradually undermine it, and promote its sinking into the sandy soil, which it does without difficulty, and altogether. When level with the surface, they raise its walls higher; and so go on, throwing out the sand and raising the wall, till they have reached the water. If they adopted our method, the soil is so light that it would fall on them before they could possibly raise the wall from the bottom; nor, without the wall, could they sink to any considerable depth." A stout square frame of wood scantling, boarded like a sentry-box, and of about the same size and shape, but without top or bottom, is used in making wells in America. The sides of a well in sandy soil are so liable to fall in, that travellers often sink a cask or some equivalent into the water, when they are encamped for any length of time in its vicinity.
Scanty wells in hot climates should be brushed over, when not in actual use, to check their evaporation.
Snow-water.--It is impossible for men to sustain life by eating snow or ice, instead of drinking water. They only aggravate the raging torments of thirst, instead of assuaging them, and hasten death. Among dogs, the Esquimaux is the only breed that can subsist on snow, as an equivalent for water. The Arctic animals, generally, have the same power. But, as regards mankind, some means of melting snow into water, for the purposes of drinking, is an essential condition of life in the Arctic regions. Without the ingenious Esquimaux lamp (p. 205), which consists of a circle of moss wicks, fed by train-oil, and chiefly used for melting snow, the Esquimaux could not exist throughout the year, in the countries which they now inhabit.
That eating large quantities of snow should seriously disturb the animal system is credible enough, when we consider the very large amount of heat that must be abstracted from the stomach, in order to melt it. A mouthful of snow at 32 degrees Fahr., that is to say, no colder than is necessary for it to be snow at all, robs as much heat from the stomach, as if the mouthful had been of water 143 degrees colder than ice-cold water, if such a fluid may, for the moment, be imagined to exist. For the "latent heat" of water is 143 degrees Fahr. In other words, it takes the same quantity of heat to convert a mass of snow of 32 degrees into water of 32º, as it does to raise the same mass of water from 32 degrees to 141º + 32 degrees = 175 degrees Fahr. It takes in practice about as long to melt snow of a low temperature into water, as it does to cause that same water to boil. Thus to raise snow of 5 degrees below zero Fahr. To 32 degrees, takes 37 degrees of heat, and it requires 143 degrees more, or 180 degrees altogether, to melt it into water. Also it requires 180 degrees to convert water of 32 degrees into water of 212 degrees, in other words, into boiling water.
Distilled Water.--It will take six or seven times as long to convert a kettle full of boiling-water into steam, as it did to make that kettle boil. For the "latent heat" of steam is 967 degrees Fahr.; therefore, if the water that was put into the kettle was 60 degrees, it would require to be raised through (212 degrees--60º degrees =) 152º degrees of temperature in order to make it begin to boil; and it would require a further quantity of heat, to the extent of 967 degrees (= about 6 1/2 times 152 degrees), to boil it all away. Hence, it is of no use to attempt to distil, until you have provided abundance of good firewood of a fit size to burn quickly, and have built an efficient fireplace on which to set the kettle. Unfortunately, fuel is commonly deficient in those places where there is a lack of fresh water.
Rate of Distillation.--A drop per second is fully equivalent To an imperial pint of water in three hours, or be an imperial gallon in an entire day and night.