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.

The simplest way to distil, but a very imperfect one, is to light a fire among stones, near a hollow in a rock, that is filled, or can be filled with salt-water.  When the stones are red-hot, drop them one by one into it:  the water will hiss and give out clouds of vapour, some of which may be collected in a cloth, and wrung or sucked out of it.  In the same way a pot on the fire may have a cloth stretched over it to catch the steam.

[Sketch of still as described below].

Still made with a Kettle and Gun-barrel.—­There is an account of the crew of the ‘Levant’ packet, which was wrecked near the cosmoledo Islands, who supplied themselves with fresh water by means of distillation alone, and whose Still was contrived with an iron pot and a gun-barrel, found on the spot where they were wrecked.  They procured, On the average, sixty bottles, or ten gallons, of distilled water in each twenty-four hours.  “The iron pot was converted into a boiler to contain salt water; a lid was fitted to it out of the root of a tree, leaving a hole of sufficient size to receive the muzzle of the gun-barrel, which was to set as a steampipe; the barrel was run through the stump of a tree, hollowed out in the middle, and kept full of cold water for the purpose of condensation; and the water so distilled escaped at the nipple of the gun-barrel, and was conducted into a bottle placed to receive it.”  The accompanying sketch is taken from a model which I made, with a soldier’s mess-tin for a boiler, and a tin tube in the place of a gun barrel.  The knob represents the breech; and the projection, through which the water is dropping, the nipple.  I may remark that there is nothing in the arrangement which would hurt the most highly-finished gun barrel; and that the trough which holds the condensing water may be made with canvas, or even dispensed with altogether.

Condensing Pipe.—­In default of other tubes, a reed may be used:  one of the long bones of an animal, or of a wading bird, will be an indifferent substitute for a condensing pipe.