Theory of Swimming. [Book VIT. 



1 for inftancc, water is poured into a glafs vefTel 

 (fig. 5.) furnilhed with a fmall cock near the bottom ; 

 if the height of the water in the vcfTel is marked with 

 a fmall bandage of thread or paper ; and, laftly, if a 

 ball of wood is thrown into it, it will appear that part 

 of the wood will be immerfed, and part of it remain 

 above the water, and that the immerfed part will raife 

 the water in the veffel juft as much as if a volume of 

 water had been added equal to the folid contents of 

 the part under water. 



If a quantity of water is then let out of the veflel 

 by means of the fmall cock, until the furface is reduced 

 as low as the mark which pointed out its height at 

 the beginning of the procefs, it is clear, that the water 

 drawn out in this, manner will be equal in its folid con- 

 tents to thofe of the immerfed part of the wooden 

 ball; and alfo, if this volume of water is weighed, it 

 will be found to be of exactly the fame weight as the 

 whole ball of wood. 



Hence it follows, that a boat upon a river difplaces, 

 a quantity of water exactly of the fame weight with 

 the boat and its lading; and if more weight is added, 

 it will fink deeper in the water in the fame proportion , 

 and the immerfed part is more or lefs in extent, ac- 



body in other animals is large, and their extremities propor- 

 tionably fmall ; in man it is the reverfe, his extremities are very 

 large in proportion to his trunk. The fpecific weight of the ex- 

 tremities is propordonably greaty than that of the trunk in all 

 animals, and therefore man muft have the greatclt weight in water, 

 fince his extremities are the largeft. 



Befides this, other animals to fwirn have only to walk (as it 

 vere) forwards upon the water ; the motion they give their limbs 

 in fwimming 1 is exaftly the fame they ufe upon land ; but it is 

 different with man, who makes ufe of thofe limbs to help him for- 

 wards upon water, which he employs to a. very different purpofe 

 upon land. ADAMS'S Licittrn, Vol. iii. p. 408. 



cording 



