The CO NTENTS. 
V. A Letter from Captain John Waddell, 
to Mr. Naphthali Franks Mercha?it , con- 
cerning the EffeSls of Lightning in deflroy- 
ing the Polarity of a Mariners Compafs ; 
to which are fubjoined fome Remarks there- 
on , by Gowin Knight, M.B. F.R.S. p. n i 
VI. A Letter frotn Sir Hans Sloane Baronet , 
late Pr. R . S. to Martin Folkes Ef quire 
Pr. R. S. containing Accounts of the pre- 
tended Serpent-ftone called Pietra de Cobra 
de Cabelos, and of the Pietra de Mom- 
bazza or the Rhinoceros Bezoar, together 
with the Figure of a Rhinoceros with a dou- 
ble Yiomffrom a Coin of Domitian. p. 1 1 8 
VII. Some Account of the Rana Pifcatrix ; by 
James Parfons, M. D. F. R. S. p. 1 26 
VIII. Obfervations on the Height to which 
Rochets afcend ; by Mr. Beniamin Robins 
F, R. S. p. 1 3 1 
IX. ExtraSl of fo much of Don Antonio De 
Ullba’r F. R. S. Account oj his V oyage to 
South America, as relates to the Dijlemper 
called 
