541 



country, now so mucli thrown on her own natm-al resoiu-ces, 

 it may help to teach us the real influences of aspects and pre- 

 vailing winds, and lead us to a scientific application of them 

 to practical purposes. Again begging your indulgence, 

 " I have the honour to remain, 

 "Dear Mr. President, 



" Your most obedient Servant, 



" Jonathan Osborne, M. D., 



" King's Prof. Mat. Med. 



''Rev. Dr. Lloyd." 



The President observed, in reference to the preceding com- 

 munication, that the cooling power of the air — as measured by 

 the time in which a thermometer, artificially heated, cooled 

 down through half the excess of its temperature above that of 

 the sm-rounding air — had been already used by Leslie to 

 measure the velocity of the wind, the effects of other causes 

 being eliminated by means of a second observation in still air. 

 This employment of a heated thermometer as an anemometer, 

 although apparently not so well known as it deserved, seemed 

 to be the most valuable application of which it was capable, 

 considered as an instrument of physical investigation. The 

 object of Dr. Osborne's inqviiries was, however, rather medical 

 than physical, and there coidd be no doubt that the means 

 which he proposed were (with some modifications) adequate 

 to the object in view. 



Dr. Apjohn suggested some additions and alterations in 

 the method of observation proposed by Dr. Osborne. 



Sir William Rovvan Hamilton gave an account of some 

 geometrical reasonings, tending to explain and confirm certain 

 results to which he had been previously conducted by the me- 

 thod of quaternions, respecting the inscription of gauche 

 polygons in central surfaces of the second order. 



