WATER. 



purgative. This water occafionally purges, but moft com- 

 monly the body becomes coftive under its ufe. " In all 

 cafes, it increafes the flow of urine, and improves the gene- 

 ral health of the patient ; fo that his appetite and fpirits 

 almoft invariably improve during a courfe of the water, if 

 it agrees in the firfl: inilance." The duration of a courfe of 

 this water depends in a great degree upon the nature of the 

 difeafe under which the patient labours. Thefe obfervations 

 upon the effefts of the Malvern water are perhaps equally 

 applicable to all fpring-waters of a fimilar degree of 

 purity. 



What has been faid of fpring-waters may be applied per- 

 haps with little modification to running waters, which m ge- 

 neral differ from yji;-/;;^- waters only in being fofter, in con- 

 taining lefs air, and m being therefore better qualified for 

 many purpofes for which fpring-waters cannot be employed. 

 Stagnant waters in general, efpecially in marfhy countries and 

 hot chmates, are ufually efteemed unwholelome, and per- 

 haps defervedly fo. This arifes chiefly from the large quan- 

 tity of vegetable and animal exuvise which they contain, and 

 perhaps from other circumftances of which we are at prefent 

 ignorant. They fhould never be ufcd, therefore, till they 

 have been boiled and filtered ; by which procefles moft of 

 the foreign fubftanccs will be probably removed. In gene- 

 ral ftagnant waters, as Dr. Saunders obferves, are unpa- 

 latable ; and this circumftance has probably cauled them to 

 be fometimes in worfe credit than they aftually deferve to be 

 on the fcore of falubrity. 



2. Simple faline Waters. — Under this denomination 

 we include all thofe waters impregnated with neutral, 

 alkaUne, and earthy falts only. Waters of this defcrip- 

 tion may be arranged under the following heads : — 

 a. Brines, or waters whofe principal faline ingredients are 

 the muriates of foda and magnefia ; and b. Bitterns, or waters 

 containing principally the fulphates of foda and mag- 

 nefia. 



a, Sea-ivater, vphich may be confidered as an example of 

 the fahne waters termed brines, is one of the moft abundant 

 andextenfively diffufed compounds occurring upon our globe. 

 When taken up at a confiderable diftance from the ftiore it 

 is quite tranfparent and colourlefs, and free from any fmell. 

 Its talle is llrongly faline, and at the fame time naufeous and 

 bitter. When kept for a ftiort time it becomes highly of- 

 tenfive, from the putrefaction of the animal and vegetable 

 matters which it holds in folution. Its fpecific gravity varies 

 in diff^erent latitudes and circumftances, but may be faid to 

 lie between 1.0269 ^"'^ 1.0285. The fpecific gravity is faid 

 to be lefs within the polar circles than at the tropics, owing 

 probably to the vaft quantities of ice found in thofe regions. 

 The waters of inland feas alfo, that have Uttle connexion 

 with the ocean, and the water of bays, &c. into which frefh- 

 water rivers empty ihemfelves, contain in general lefs faline 

 matters than the open ocean. This is particularly the cafe 

 with the Baltic, elpecially when the wind blows from the 

 eaft. The Mediterranean fea, on the contrary, is faid 

 to be more faline than the Atlantic. Water taken from a 

 confiderable depth is more fahne than that taken from the 

 furface, particularly after much rain, for rain-water being 

 lighter appears to move upon the furface for a confiderable 

 time before it becomes quite incorporated. The quantity of 

 faline matter alfo is ftated to be greater in fummcr than in win- 

 ter. The water of the Britifli coafts is faid to contain upon 

 an average about one-thirtieth of its weight of faline matter, 

 and its temperature to vary between 40° and 65°. Sea-water 

 does not freeze till cooled down to 28. "5. The following 

 is one of the lateft analyfes of fea-water by Dr. Murray. A 



wine pint of water colleAed in the Firth of Forth was found 



to contain 



Grains, 

 Of lime .... 2.9 



Magnefia .... j^^.g 



Soda . . . - 96.3 



Sulphuric acid ... 14.4 



Muriatic acid ... gy.y 



226.1 



Or, fuppofing the elements to be combined in the modes 

 in which they are obtained by evaporation ; that is, as mu- 

 riate of foda, muriate of magnefia, fulphate of magnefia, 

 and fulphate of lime, the proportions of thefe falts in a pint 

 will be, 



Grains. 

 Muriate of foda - - - 180.5 



of magnefia - - 23. 



'Sulphate of magnefia - - 15.5 

 of linie - - .7.1 



226. 



Or, fuppofing that the lime exifts as muriate of lime, 

 (v.'hich is the moft probable conclufion with regard to it); 

 and farther, fuppofing that the fiilphuric acid exifts in the 

 ftate of fulphate of mai^nefia, the proportions will be, 



Grains. 

 Muriate of foda '- . - 180.5 



: of magnefia . - 18.3 



of lime - . . 5.7 



Sulphate of magnefia - - 21.6 



226.1 



Or, laftly, fuppofing that the fulphuric acid exifts in 

 the ftate of fulphate of foda, the proportions will be, 



Muriate of foda 



of magnefia 



of lime 



Sulphate of foda 



Grains. 



35-5 



5-7 



25.6 



226.1 



The bitter tafte of fea-water is owing chiefly to the mu- 

 riate of magnefia which it contains. It may alfo arife, in 

 part, from the prefence of decayed vegetable and animal 

 fubftances. See the articles Salt, Saltness, and Sea. 



Many attempts have been made to render fea-water po- 

 table. Of thefe the beft, and indeed the only good one, is 

 diftillation. 



The method of obtaining freih water from the diftillation 

 of fea-water was praftifed by fir R. Hawkins, in the reign 

 of queen Elizabeth, who thus obtained water that was 

 wholefome and nouriftiing. See Purchas's Colledt. of 

 Voyages, book vii. chap. 5. 



Experiments were afterwards made by Hales, Lifter, 

 Hanton, Lind, and others, to fimphfy and render more per- 

 feft the procefs of diftillation, and at length it attained a 

 great degree of perfetlion, both in France and England. 

 Thus M. de Bougainville, in his Voyage round the World, 

 bore ample teftimony to the utility of the machine for dif- 

 nlling fea-water, which had been made pubhc in 1763 by 

 M. Poiflbnnier, its inventor ; and lord Mulgrave, in his 



Voyage 



