208 HISTORY OF 



motion, therefore, and not the saltness of the sea 

 that preserves it in its present state of salubrity ; 

 and this, very probably, by dashing and breaking 

 in pieces the rudiments, if I may so call them, of 

 the various-, animals that would otherwise breed 

 there, and putrefy. 



There are some advantages, however, which are 

 derived from the saltness of the sea. Its waters 

 being evaporated, furnish that salt which is used 

 for domestic purposes; and, although in some 

 places it is made from springs, and in others dug 

 out of mines, yet the greatest quantity is made 

 only from the sea. That which is called bay salt, 

 (from its coming to us by the Bay of Biscay), is a 

 stronger kind, made by evaporation in the sun ; 

 that called common salt, is evaporated in pans 

 over the fire, and is of a much inferior quality 

 to the former. 



Another benefit arising from the quantity of 

 salt dissolved in the sea, is, that it thus becomes 

 heavier, and, consequently, more buoyant. Mr 

 Boyle, who examined the difference between sea 

 water and fresh, found that the former appeared 

 to be about a forty-fifth part heavier than the lat- 

 ter. Those, also, who have had opportunities of 

 bathing in the sea, pretend to have experienced a 

 much greater ease in swimming there, than in 

 fresh water. However, as we see they have only 

 a forty-fifth part more of their weight sustained 

 by it, I am apt to doubt whether so minute a dif- 

 ference can be practically perceivable. Be this 

 as it may, as sea water alters in its weight from 

 fresh, so it is found also to differ from itself in 



