VOL. XXXIII.] PHILOSOPHICAL TKANSACTIONS. 6y 



roidical figure of the earth cannot be consistent with the experiments on 

 pendulums. 



And now. Dr. D. thinks he has answered all that relates to the figure of the 

 earth in M. Mairan's Dissertation ; in showing, that his conjectures can neither be 

 supported by those physical principles, which Sir Isaac Newton has mathematically 

 deduced, from unquestioned observations and experiments accurately made ; nor 

 even by those principles which M. Mairan has assumed to serve his intended 

 purpose: — That his demonstrations relating to the difference of the action of 

 the centrifugal force, are of no service to him, for reconciling the experiments 

 made on pendulums, with M. Cassini's measures ; — because, when applied to 

 Sir Isaac Newton's principles, they will make pendulums longer at the equator 

 than at Paris, and when applied to M. Mairan's own principles, they will make 

 them a whole inch shorter at the equator than at Paris, contrary to all observa- 

 tions, which at a medium, make pendulums but about 1 lines or -l'tto of an 

 inch longer at the equator than at Paris : — That he has built his demonstrations 

 on a wrong notion of gravity : — And that he has not considered what is most 

 material in the effect of the centrifugal force, acting on bodies descending by 

 their gravity, between the equator and the poles, namely, the alteration of their 

 line of direction, which would make them fall out of the perpendicular towards 

 the equator. 



To conclude, the Doctor proposes a method of observing the figure of the 

 shadow of the earth in lunar eclipses, by which the difference between the dia- 

 meters in the oblong spheroidical figure, if there be such a one as M. Cassini 

 affirms, viz. of 96 to 95, may be discovered. 



If therefore those astronomers who have instruments nice enough, and suf- 

 ficient skill in the management of them, to take angles to 3 or 4 seconds of a 

 degree, will observe what has been mentioned in total and partial eclipses of the 

 moon ; by such observations they will easily convince us that the figure of the 

 earth is such as M. Cassini supposes it, or convince him that he has been 

 mistaken. 



Some Observations on an Ostrich, dissected by Order of Sir Hans Shane, Bart. 

 By Mr. John Ranby, Surgeon, F. R. S. N° 386, p. 223. 



Having separated the muscles of the abdomen, which in this subject were 

 only 2 oblique pair, they observed, between their tendons, which were very 

 strong, and the peritoneum, which was exceedingly thin, a thick layer of sevous 

 fat, whose office, considering the smallness of the epiploon, and the few adi- 

 pose vesicles of the mesentery, with the thinness of the peritoneum, might 



