220 



Fahr. approaches to C40 H,j4 ; there being, however, a shght ex- 

 cess of oxygen, and water not being the only volatile compound 

 driven off. 



The resin of opoponax, when thus heated the hydrogen, as in 

 that of re tin asphalt, remains nearly constant = C40 H25 O14, ap- 

 proaching to C40 H25 O12. The same is the case with the resin of 

 assafoetida (= C40 H^g Ojo), which by prolonged heating at about 

 250° Fahr., becomes C40 Hcjg Og. These observations when multi- 

 plied are likely to assist materially in leading to rational formulae, 

 expressive of the molecular constitution of the resins. 



In reference to the general questions, with a view to the solution 

 of which the author undertook this investigation, he concludes : 



1. That the resins are not to be considered as different com- 

 pounds of one and the same radical, but rather as analogous groups 

 of compounds of analogous radicals. 



2. That as far as our present knowledge extends, all the true re- 

 sins are capable of being represented by irrational formulae, in which 

 C40 is a constant quantity. 



3. That the analyses contained in the present paper render ne- 

 cessary a slight modification in the general formulae previously an- 

 nounced. The formula for the group of which colophony is the 

 type, being C40 H32 + .r Oy ; and that for the group of which gam- 

 boge or dragon's blood is the type, being C40 H24 + x Oy. 



The author announces a further continuation of these researches, 

 in which the constitution of other resins will be given, and the re- 

 lations of the resins to certain chemical reagents will be explained 

 and illustrated. 



The Society then adjourned over the Easter Recess, to meet again 

 on the 30th instant. 



April 30, 1840. 



The MARQUIS of NORTHAMPTON, President, in the Chair. 



His Royal Highness Prince Albert, of Saxe Coburg and Gotha, 

 K.G., was proposed as a Fellow of the Royal Society by the Presi- 

 dent, seconded by John W. Lubbock, Esq., V.P. and Treasurer 

 R.S., and, being put to the ballot, H.R.H. was elected a Fellow of 

 the Royal Society. 



Lord Lyttleton was also, pursuant to a notice given at the last 

 meeting, put to the ballot, and elected a Fellow of this Society. 



Thomas Wharton Jones, Esq., and John Grant Malcolmson, M.D., 

 were also balloted for, and duly elected into the Society. 



The following communications were read : — 

 1. A Letter from Sir John Barrow, Bart., V.P., addressed to the 

 President, accompanying a series of Magnetic Observations made on 



