284 



concentrate and decussate in the same manner ; thus agreeing in 

 every respect, except in the nervous filaments to which thev give 

 origin. Hence he explains the phenomena of the loss of sensibilitv 

 as well as the power of motion of one side of the body, consequent 

 on injuries of the other side of the brain. 



The Society then adjourned over Whitsun Week to the 29 th of May. 



May 29, 1634. 



JOHN WILLIAM LUBBOCK, Esq., M.A., V.P. and Treasurer, 

 in the Chair. 



A paper was read, entitled, " On the Principle of Construction and 

 General Application of the Negative Achromatic Lens to Telescopes 

 and Evepieces of every description." By Peter Barlow, Esq.. F.R.S. 



This paper is intended as a more full illustration of the principles 

 on which the negative achromatic lens is constructed and applied, than 

 has been given in the extract from the author's letter to Mr. Dollond, 

 contained in the paper of the latter, lately read to the Society, on his 

 ingenious application of that lens to the micrometer eyepiece. The 

 author shows that its advantages are not confined to this instrument, 

 but that it is applicable to any eyepiece positive or negative to the 

 erecting evepiece. and, indeed, to any telescope of fluid or glass, and 

 also to refractors. 



A paper was also read, entitled, " Some remarks in reply to Dr. 

 Daubenv s Note on the Air disengaged from the Sea over the site of 

 the recent Volcano in the Mediterranean." By John Davy, M.D., 

 F.R.S. Assistant Inspector of Army Hospitals. 



Respecting the air in question, which Dr. Davy had found to con- 

 sist of about SO per cent, of azote and 10 oxygen, he had remarked 

 that two views might be taken of its origin ; the one, that it was of 

 volcanic source ; the other, that it was derived from the sea water, 

 and merely disengaged by the heat of the volcano. Dr. Davy, reject- 

 ing the former of these views, had adopted the latter, for reasons, the 

 validity of which was controverted by Dr. Daubenv : and the purpose 

 of the present paper is to answer the objections urged against them, 

 and to bring additional evidence in support of his opinion. 



A paper was then read, entitled. •'•'On the , number of Primitive 

 Colorific Rays into which White Light may be separated." By Paul 

 Cooper, Esq. Communicated by J. G. Children, E^q. Sec. R.S'. 



From a consideration of the circumstances in which white light is 

 decomposed by the prism, in different experiments, and of the various 

 appearances of the spectra which result, the author is led to the 

 opinion that the primary colours composing white light are not 

 seven, as conceived by Newton : nor four, as supposed by Wollas- 

 ton ; but only three: and that these three are not red, yellow, and 



