XQ EXPERIMENTS AND OBSERVATIONS ON THE 



opinion evidently verified ; that the nearer a menifcus ap« 

 proaches to a piano, the more perfe6l it will be, as the fpherical 

 lurface^ for the fame focus, is diminiflied, and confequently 

 the aberration befides; admitting that there were any advantage 

 defirable from a great obliquity of the axis of the eyes to 

 thofe of the minifcus (haped fpedacle glalFes. I would afk, 

 for what reafon has man his head moveable ? was it not^ that 

 he fliould place his eyes dire6tly before the obje6t to be viewed, 

 and not fubjed himfelf to fallacious ideas of them, by an 

 aukvvard and revolutionary fquinting. From what I have 

 advanced, I doubt not of the public decifion, (from a fair 

 comparifon of the two kinds of fpedacles) in favour of the 

 eflablillred double convex fpedlacle-glafles, for 

 <' Magna efi Veritas et preevalebit.'* 

 I am, Sir, 



Your refpedlful humble Servant, 



W. JONES. 



Ilolborn, April 10, ISOk 



XL 



Experiments and Obfertatiom on the Change ivhich (he Air of the 

 Atmnfphere undergoes by Refpiraiion, particularly uith Regard 

 to the Ahforption of Nitrogen. In a Letter from Alexander 

 Henderson, M. D. 



To Mr. NICHOLSON. 

 SIR, 



Whether nltro- 1 TAKE the liberty of communicating to you a brief detail 



gen be abforbed ^f f^j^g experiments on refpiration, which were undertaken 

 in refpiration. , • « ■ / . 



chiefly with a view to determine the abforplion or non-ab- 



forption of nitrogen, a point which has been hitherto much 

 controverted, but which I flatter myfelf to have now fuf- 

 ficiently afcertained. 

 The gafomcter. Thefe experiments were performed by means of a gafo- 

 meter, capable of containing about 2200 c. inches, and gra- 

 duated fo as to fliew a difference of 2 C. inches. In breathing 

 from this apparatus, the inconveniences from fri6lion were very 

 inconfiderable. Towards the end of the experiment, how- 

 ever. 



