121 HISTOIIY OF 



that of a purer kind. We know that it is so with regard to 

 vegetables : and why not, also, in general, to man ? Be this as- 

 it will, if we are desirous of having water in its greatest purity, 

 we are ordered, by the curious in this particular, to distil it from 

 snow, gathered upon the tops of the highest mountains, and to 

 take none but the outer and superficial part thereof. This we 

 must be satisfied to call pure water ; but even this is far short 

 of the pure unmixed philosophical element ; wliich, in reality, is 

 nowhere to be found. 



As water is thus mixed with foreign matter, and often the re- 

 pository of minute animals, or vegetable seeds, we need not be 

 .surprised that, when carried to sea, it is always found to putrefy. 

 But we must not suppose that it is the element itself which thus 

 grows putrid and oifensive, but the substances with which it is 

 impregnated. It is true, the utmost precautions are taken to 

 destroy all vegetable and animal substances that may have pre- 

 viously been lodged in it, by boiling ; but, notwithstanding this, 

 there are some that will still survive the operation, and others 

 that find their way during the time of its stowage. Seamen, 

 therefore, assure us, that their water is generally found to putre- 

 fy twice, at least, and sometimes three times, in a long voyage. 

 In about a month after it has been at sea, when the bung is taken 

 out of the cask, it sends up a noisome and dangerous vapour, 

 which would take fire upon the application of a candle.' The 

 whole body of the water then is found replete with little worm- 

 like insects, that float, with great briskness, through all its parts. 

 These generally live for about a couple of days ; and then dying, 

 by depositing their spoils, for a while increase 4:he putrefaction. 

 After a time, the heavier parts of these sinking to the bottom, 

 the lighter float in a scum, at the top ; and this is what mariners 

 call the water's purging itself. There is still, however, another 

 race of insects, which are bred, very probably, from the spoils of 

 the former ; and produce, after some time, similar appearances : 

 these dying, the water is then thought to change no more. How. 

 ever, it very often happens, especially in hot climates, that no- 

 thing can drive these nauseous insects from the ship's store or 

 water. They often increase to a very disagreeable and frightful 

 gize, so as to deter the mariner, though parching with thirst, from 

 tasting that cup which they have contaminated. 



1 Phil. Trans, vol. v. part ii. p. 71 



