474 Saltmjs of [Book VII. 



on the degree of faltnefs- of the ocean in particular 

 latitudes were made till the prefent century, and it is 

 not poflible, therefore, to afcertain ^vhat was theftatff 

 of the fea at any confidcrable diftance of time, nor, 

 confequently, whether its degree of faltnefs increafes, 

 decreafes, or is fbttionary. From differences arriong 

 aquatic animals, however, fome of which feem adapted 

 to fait water, and fome to frefh, it is probable, that both. 

 thefe flates of water exifted from the creation of the 

 world. We know it is true^ that fome kinds of fifh, 

 as falmon, are capable of exifting both in frefh and in 

 fait water, and that habit has a powerful influence over 

 all animals j but this is not fufficient to refute the main 

 fact, that fome kinds of fiih thrive only in fait water, 

 others in frefh 3 fome in Handing pools, and others in 

 rapid currents. 



That excellent philofopher and chemift, to whofe 

 labours I am indebted for fome of the moft valuable 

 parts of thefe volumes, the bifliop of Landaff, has re- 

 commended a moil fimple and eafy mode of afcer- 

 taining the faltnefs of the fea in any latitude ; and as 

 the language, in point of perfpicuity and correclnefs, 

 cannot be improved, I fliall take the liberty of inferring 

 it in his own words. 



c As it is not every perfon who can make himfelf 

 expert in the ule of the common means of eftimating 

 the quantity of fait contained in fea water, I will men- 

 tion a method of doing it, which is fo eafy and fimple, 

 that every common failor may underftand and praftiic 

 it, and which at the fame time, from the trials I have 

 made of it, feems to be as exact a method as any that 

 has yet been thought of. Take a clean towel or any 

 other piece of cloth, dry it well in ihe fun or before 

 the fire, then weigh it accurately, and note down its 

 weight,* dip it in the fea water, and, when taken out, 



\vrins 



