A HISTORY OF 



supposed live iVoin all these, it is mixed with 

 u quantityof air, which, after being kept for 

 some time, will be seen to separate. 



Spring-water is next in point of purity. This, 

 according to Dr. Halley, is collected from the 

 air itself; which being sated with ^yater, and 

 coming to be condensed by the evening's cold, 

 is driven against the tops of the mountains, 

 where being condensed and collected, it 

 trickles down by the sides, into the cavities 

 of the earth ; and running for a while under- 

 ground,bubbles up in fountains upon the plain. 

 This having made but a short circulation, has 

 generally had no long time to dissolve or im- 

 bibe any foreign substances by the way. 



River-water is generally more foul than the 

 former. Wherever the stream flows, it re- 

 ceives a tincture from its channel. Plants, 

 minerals, and animals, all contribute to add 

 to its impurities : so that such as live at the 

 mouths of great rivers, are generally subject 

 to all those disorders which contaminated and 

 unwholesome waters are known to produce. 

 Of all the river-water in the world, that of the 

 Indus and the Thames is said to be the most 

 light and wholesome. 



The most impure fresh water that we know, 

 is that of stagnating pools and lakes, * Inch, 

 in summer, may be more properly considered 

 as a jelly of floating insects, than a collection 

 of water. In this, millions of little reptiles, 

 undisturbed by any current, which might crush 

 their frames to pieces, breed and engender. 

 The whole teems with shapeless life, and 

 only grows more fruitful by increasing putre- 

 faction. 



Of the purity of all these waters, the light- 

 ness, and not the transparency, ought f o be 

 the test. Water may be extremely ck a.r and 

 beautiful to the eye, and yet very much im- 

 pregnated with mineral particles. In fact, 

 sea-water is the most transparent of any, and 

 yet it is well known to contain a large mix- 

 ture of salt and bitumen. On the contrary, 

 those waters which are lightest, have the few- 

 est dissolutions floating in them ; and may, 

 therefore, be the most useful for all the pur- 

 poses of life. But, after all, though much has 

 been said upon this subject, and although wa- 

 ters have been weighed with great assiduity, 

 to determine their degree of salubrity, yet 

 neither this, nor their curdling with soap, nor 



any other philosophical standard whatsoever, 

 will answer the purposes of true information. 

 Experience alone ought to determine the use- 

 ful or noxious qualities of every spring ; and 

 | experience assures us, that different kinds of 

 1 water are adopted to different constitutions. 

 I An incontestable proof of this, are the many 

 i medicinal springs throughout the world, whose 

 i peculiar benefits are known to the natives of 

 their respective countries. These are of va- 

 rious kinds, according to the different miner- 

 als with which they are impregnated ; hot, 

 saline, sulphureous, bituminous, and oily. But 

 the account of these will come most properly 

 under that of the several minerals by which 

 they are produced. 



After all, therefore, we must be contented 

 with but an impure mixture for our daily be- 

 verage. And yet, perhaps, this very mixture 

 may often be more serviceable to our health 

 than 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 ; which, 

 in reality, is no where to be found. 



As water is thus mixed with foreign matter, 

 and often the repository 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 offensive, but the substances with which 

 it is impregnated. It is true, the utmost pre- 

 cautions are taken to destroy all vegetable 

 and animal substances that may have previ- 

 ously been lodged in it, by boiling ; but, not- 

 withstanding this, there are some that will 

 still survive the operation, and others that find 

 their way during the time of its stowage. Sea- 

 men, therefore, assure us, that their water is 

 generally found to putrefy 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 

 o noisonie and dangerous vapour, which 



