WATER OF THE OCEAN. 143 



paratively rare or fcarce, the latter is the predominating 

 compound. When there is any acid in the water beyond 

 the capacity of the Ibda exifting tliere to neutraHze, that 

 part is attracted by the two earths, and according to the 

 force of their refpedive combinations, forms fulphates, 

 feptates and muriates of lime and magnefia. 'Ihefe falts 

 with earthy bales, in which the muriatic acid is by faf 

 more abundant than the other two acids, conftitute the 

 bittern and fcratch or Jlack of the fait makers. Thefe 

 falited earths attract water fo ftrongly that it is difficult 

 or impoifible to make them cryliallize ; but wherever 

 they are they keep up a dampnefs and refufe to dry. 



When chemifts fpeak of fea fait they wifh to be un- 

 derflood as meaning " the pure muriate of ibda." This 

 neutral compound however in its pure flate is a great 

 rarity. Perhaps indeed there is no fuch thing. Expe- 

 rience fhews it is always mingled with greater or lefs 

 quantities of the dellquefcent Jalts with earthy bafes. 

 And thefe are fo abundant in fome forts of fait that they 

 render it unfit for the prefervation of animal provifions. 

 Beef and even pork, are not guarded by fait fo adulter- 

 ated, from becoming tainted and putrid. That fea fait 

 of this impure quality fhould be fit for curing provifions, 

 it ought to undergo a particular refining operation to rid 

 it of its foreign admixtures. For want of fuch a procefs, 

 fome forts of fea fait, though fair to the eye, do not 

 poffefs an intire and undivided antifeptic power, but fo 

 far as the muriate of foda in the mafs is alloyed by the 

 middle falts of magnefian and calcarious compofition, 

 thofe parcels of common fait fo vitiated become unfit for 

 oppofing completely the procefs of putrefaction. And 

 fo far they make a departure from the antifeptic power 

 of pure muriate of foda, the manner of whofe adion, 

 1 endeavoured to inveftigate in a Memoir addreffed to 



U 2 profeflbr 



