[ 214 ] 
fometimes half a day without one’s being able to difcern 
in him any motion for the refpiration. 
From this it is eafily feen, that they can retain 
infpired air a long time : and the Academicans there- 
fore think, that the principal ufe of the lungs in 
tortoifes, is to render themfelves fpecifically lighter or 
heavier in the water, by their inflation and compreflion 
at will, as fifhesdo by their fwimming bladders; indeed 
fuch a power of long infpiration feems to be as necef- 
lary in the land tortoife as in that of the fea ; becaufe, 
in many countries where they breed, they are known 
to go into the ground and lye concealed for feveral 
months ; and it is well known, that feveral fpecies 
of land tortoifes go into ponds or canals in gardens, 
where they are kept, and remain long under water at 
pleafure. Of this my worthy friend Mr. Collinfon 
had inttances in his gardens at his country feat : and I 
law two land tortoifes in the bottom of a circular 
canal, in the gardens of the Palais Royal in Paris feveral 
times, which were very large ones, and remained 
under water many hours together. 
The ingenious Academicians, however, in order to 
verify their fentiments, that one principal ufe of the 
lungs in a tortoife is to render them capable of 
remaining at any depth in the water at will, made the 
following experiment : they locked up a living tortoife 
in a veflel of water intirely full ; on which there was 
a cover exadly fattened with wax, from which there 
went a glafs pipe: the veflel being full, fo as to make 
the water'appear at the bottom of the glafs pipe; they 
oblerved the water did fometimes attend into the 
pipe, and that it fometimes dettended. Now this 
could be done only by the augmentation and dimi- 
nution 
