84 Royal Society of London^ 



gressive spreading of his legs, till his belly falls on the 

 wheel ! 



Man alone, from his erect position, and his facility of 

 hanoing or bearino; discrctionally by his hands on a fixed 

 rail, seems capable of applying muscular power with advan- 

 tage to the convex surface of a moving wheel. 



I am sir, your obedient servant, 



. Westminster, MecHANICUS junior. 



Feb. 14, 1807. 



XV. Proceedings of Learned Societies. 



ROYAL SOCIETY OF LONDON. 



Jan. 29, 1S07. The right hon. the earl of Morton, vice- 

 president, in the chair. — Continuation of Dr. Hcrschel's 

 paper on the coloured concentric rings* seen through thin 

 plates or lenses. The doctor detailed a great variety of expe- 

 riments made with lenses of 120 feet focus down to those of 

 the most common glasses. The colours of these rings seen 

 through the lens of 120 feet were black and white; those 

 through one of 40, were red j those through one of 14, were 

 violet, &c. Thus these concentric rings, which through a 

 glass of one focus appeared black, through another appeared 

 blue, and so on throughout the whole series of the prismatic 

 colours. The author drew no conclusions from these facts, 

 nor did he attempt to classify them in any manner tending 

 to elucidate the nature of the phaenomena, or the peculiar 

 influence of s!;lasses of different densities on the transmissi- 

 bility of light. 



Feb. 3. Right hon. C. F. Greville, vice-president, in the 

 chair. — The reading of the above paper was concluded. The 

 doctor made numerous other experiments, all of which tended 

 to establish the fact, that light could not have, as sir Isaac 

 Newton supposed, fits of easy transmission or reflection; 

 and that therefore this phaenomenon of concentric rings 

 must be ascribed to another cause, which he proposed to 



* In our last Number, the words " circular rtiys" occur instead of " con- 

 centric rings." . 



investigate 



