VOL. XVII.J PHtLOSOPHICAt. THANSACTIONS. ^ 45p 



Observations on ike fVeight of a Land-Tortoise at the Time of its retiring under 

 Ground in /Autumn, compared with its Weight on its Re-appearance in Spring ; 

 repeated for a Series of Years. By George Ent, M. D. Communicated by 

 Robert Pitt, M.D. F.R.S. Translated from the Latin. N° 194, p. 533. 



Oct. 7, 1652. — The tortoise being weighed before it withdrew to its winter 

 retreat, its weight was found to be exactly 4 lb. 3oz. 7drs. 



Oct. 8, 1652.— Being dug up the day after it had gone under ground, it 

 weighed 4 lb. 6oz. idr, 



March 16, l653. — (Being the day on which it came out of its hole) it weighed 

 4 lb. 4oz. 



Oct. 4, 1633. — After it had fasted for some days and had gone under ground, 

 it was found, on being dug up, to weigh 4 lb. 5oz. 



March 18, l654. — On which day it again came out of its retreat, it weighed 

 4lb. 4oz. 2drs. 



Oct. 6, 1654. — When it was about going into winter-quarters again, it 

 weighed 4 lb. goz. 3drs. 



On the last day of Feb. l655. — On again coming out of its hole, it weighed 

 41b. 70Z. 6drs. It therefore lost of its former weight 1 oz. 5drs. 



Oct. 2, 1653. — When it was on the point of retiring again, it weighed 4lb. 

 Qoz. ; but it had previously left off taking food, for some time. 



March 25, iSsS. — On its re-appearance it weighed 4 lb. 7oz. 2drs. 



Sept. 30, 1656. — When it was about to bury itself again, it weighed 4 lb. 

 12oz. 4drs. 



March 5, 1657. — On again coming above ground, it weighed 4lb. lloz. 

 2J drs. 



Of the Thickness of Gold on Gilt- Wire, and the exceeding Minuteness of the 

 Atoms or constituent Particles of Gold. By E, Halley. N° 194, p. 540. 



What are the constituent parts of matter, and how there happens to be so 

 great a diversity in the weight of bodies, to all appearance equally solid and 

 dense, such as are gold and glass, whose specific gravities are nearly as 7 to I, 

 seems a very hard question to those who rightly consider it : for, from un- 

 doubted experiment, gravity is in all bodies proportionable to the quantity or 

 matter in each, and there is no such thing as a propension of some more, others 

 less, towards the earth's centre ; since, the resistance of the air being removed, 

 all bodies descend, be they ever so loose or compact in texture, with equal 



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