( 6 s y 
mcunttoat leaft. i 2006 Gubick feet> befidts many other 
abfurditys. 
He defcribes the aStlon of fwiinming, and how fiflies 
change their fpecified gravity on occafion, by thecom- 
preCfion and dilatation of the Air contained in their ^^r« 
Bladders y performed by the many and ftrong mufcles a- 
bout their bellies; 
He afligns the reafon why man does not Swim by In- 
ftinft^ as well as other Animals ^ to be chiefly on the ac- 
count of the gravity of the head io much exceeding the 
proportion of that of the reft of the body. 
The feveral ways to live and move under Water were 
defcribed before as the the leathern Cylinder ^c. but 
rhat which he feems moft to infifton, isofaBrafsor 
Coper Vejica about two foot diameter to contain the Di^ 
vers head, this to be faftnedto* Goats skin habit fitted 
exa£tly to chefbape of the body. He contrives a Circulati- 
m for the Air by pipes within the ^<?y{i:^ : and beftows 
on him an Air-^ump by his fide > by which he may make 
himfelf heavier or lighter, in imitation of the engines 
Nature has given to Fifli for thatufe. By this means he 
avoids the objections the others are liable to , particu- 
larly that of the Air , ihemoiftureby which it is clogged 
with in expiration , andby it made unfit for the fame ufe 
again , being here taken from it by its Circulation through 
the pipes ^ to the fides of which it adheres^ and leaves the 
air as untainted as before. 
He concludes the book with a defcription of the diving 
Ship* The motion of which he conceives would be much 
facilitated by one fingleoar in the Poop, which fhould b^ 
flexible,&made w'** a fpring> fromthe vibration of which 
thefhipftiould be impelled as Piflies are by their Tails. 
In the lecond part he complcats the Do^rine fo well 
begun in thefirft, and layes down the Mechanical Mode 
and immediate caufe by , which the cpntraftion of the nouf- 
ties is perfbrmed>-^\$ -^^^r^v-^ z^h '^'H ^-"i '^i ■ ' 
In the Firft place he (hews why a Mufcle cannot be mof e4 
1 an/ 
