400 PHILOSOPHICAL TRANSACTIONS. [aNNO 16Q2-3. 



But here it may be objected, that the experiments have been made only on 

 waters impregnated with gross or corporeal sea-salt, which perhaps may not 

 hinder, but that they may be imbued with the spirits of marine salt, which, by 

 reason of their activity, may be as unhealthful to the drinker as the grosser salt 

 itself. But though to this surmise I might answer, that a very small propor- 

 tion of spirit of salt may in many cases make the water seasoned with it rather 

 medicinal than unwholesome ; yet I shall answer more directly to the objection, 

 by saying that to manifest its not being well grounded, I took above 1000 grs. 

 of distilled water, and, instead of gross salt, put to it one single drop of 

 moderately strong spirit of salt, and having shaken it into the water, I let fall 

 into a portion of this unequally composed mixture, some drops of our solution 

 of silver, which presently began to precipitate in a whitish form ; insomuch that 

 this trial succeeded better than if the water had been impregnated with but 

 1000th part of gross salt. And to pursue this trial further, I had the 

 curiosity to diffuse 1 drop of spirit of salt into 2000 grs, of distilled rain-water; 

 and on letting fall some drops of our precipitant into it, I found that the suc- 

 cess answered my expectation. And then to urge the trial yet further, I added 

 as much of the same distilled rain-water, as by a moderate conjecture made it 

 amount to at least half as much more. So that 1 grain of spirit of salt had a 

 manifest operation, though not quite so conspicuous as the former, on above 

 3000 grs. of water, whose immunity from common salt was tried apart. And 

 that a drop of the saline spirit we made use of did not equal in weight 1 grain 

 of dry salt, I found by this, that having let fall into a counterpoised piece of 

 glass, 10 drops of that spirit, I found them to want near -l gr. of 9 grs. weight. 

 The like trial I made by substituting above 1000 grs. of rain-water, in the 

 room of the like quantity of distilled water. And perhaps it will not be im- 

 pertinent to add on this occasion, that in some places, especially lying in hot 

 climates, it may sometimes be of use to know whether, on account of the sun's 

 heat, or that of the subterraneal regions of the earth, the rain-water is im- 

 pregnated with volatile (not acid) spirits, like those that are distilled from urine, 

 and which I have, for curiosity's sake, obtained from a mineral body, native sal- 

 ammoniac ; on which account I made a trial, that informed me, that if 5 or 6 

 drops of strong spirit of urine were shaken into 1000 grs. at least of distilled or 

 rain-water, impregnated with but one of salt, our precipitant would make a dis- 

 covery of some saltishuess in the liquor. And for ought I have yet observed, 

 not only such undistilled waters as are generally allowed to be freely potable, 

 but even those that nature herself distils, are not always quite devoid of salt- 

 ness : for I have found rain-water that I caused to be carefully saved, after the 

 bouse-tops had been newly well washed with former rain, to grow a little 



