[ 20 ° ] 
confiderable time; yet his chief refidence is upon land, 
and he muft come on fhore for refpiration. 
The teftudo, or fea-tortoife, though he goes out to 
lea, and is often found far from land ; yet, being a 
refpiring animal, cannot remain long under water. 
He has indeed a power of rendering himlelf fpecifl- 
cally heavier or lighter than the water, and therefore 
can let himfelf down to avoid an enemy or a ftorm ; 
yet he is under a neceflityof rifingfrequently to breathe, 
lorreafons given before : and his mod: ufual fituation, 
while at fea, is upon the furface of the water, feeding 
upon the various fubftances that float in great abun- 
dance every where about him ; thele animals fleep 
fecurely upon the furface, but not under water, and 
can remain longer at fea than any others of this clafs, 
except the crocodile, becaufe, as it is with the latter, his 
covering is not in danger of being too much mace- 
rated ; yet they muft go on fhore to copulate and lay 
their eggs. 
The conflderation of thefe is fufficient to inform 
us of the nature of the far ft order of the clafs of 
amphibious animals ; let us now fee what is to be faid 
of the fecond in our divilion of them, which are fuch 
as chiefly inhabit the waters, but occaflonally go on 
fhore. 
Thefe are but of two kinds : the eels and water- 
lerpents, or fnakes of every kind. It is their form that 
qualities them for loco- motion on land, and they know 
their way back to the water at will; for by their 
ftru&ure they have a ftrong periftaltic motion, by 
which they can go forward at a pretty good rate, 
whereas, all other kinds of fifh, whether vertical or 
horizontal, are incapable of a voluntary loco-motion on 
6 fhore ; 
