Minerals of Organic Origin. — Mineral Resins. 93 



of the resins which exude from the pines of warm cHmates to 

 justify us in attaching much weight to this last conjecture that it 

 has undergone a change since it was deposited. Colophony 

 is C.20 Hjg O, so that this resin might be formed by substituting 

 an atom of carbonic acid for one of hydrogen, since 

 C,oHi,0-H+C02=C,iHi,03 



3. Middletonite * = C20 Hn O. 



From the circumstances under which this substance occurs 

 in the coal of Yorkshire and Staffordshire in thin layers and 

 masses in the body of the coal, I have already stated that it is 

 to be regarded as the altered resin of the trees of the epoch of 

 the great coal formation. That it has undergone a change is 

 evident not merely from its properties, but from the apparent 

 impossibility that a resinous substance should remain unal- 

 tered while the wood which enveloped it was converted into 

 coal. Mr. Embleton, the intelligent viewer of the Middleton 

 coal mines, considers the opinion of its being a changed resin 

 to be confirmed by the appearance of the coal with which 

 it is in contact, which appears to him to bear a close resem- 

 blance to a changed bark. 



The pseudo resin of Settling stones is probably no further 

 of vegetable origin than that it may have been distilled or 

 volatilized out of vegetable matters scattei-ed throughout the 

 dark shale and other rocks with which the trap, near which it 

 is found, had come into contact while in a fluid state. 



1 - fGui/aquillitef = C40 Hgg Og 



4. and 5. \ji,iJg,ut, = Cl H31 O3. 



With the geological position of these two substances I am 

 wholly unacquainted. The one is said to form large deposits 

 in the neighbourhood of Guyaquil, the other to occur at least 

 15 degrees further south, forming a species of lake. The 

 proximity of the volcanic chain to both localities, the former 

 beinfr almost at the foot of Chimborazo, renders it not un- 

 likely that they may be, or may have been, distilled from ve- 

 getable deposits lying beneath ; and though true resins have 

 seldom been met with except in substances of known vegetable 

 origin, yet since the petroline of Boussingault contains carbon 

 and hydrogen in the same proportions as in oil of turpentine, 

 there is no difficulty in conceiving that under favourable cir- 

 cumstances tliis and other compounds of similar constitution, 

 existing in deposits of petroleum, may undergo oxidation and 

 produce resins similar to those actually found as mineral 

 productions in South America. Before we can obtain clear 

 ideas on the subject however, we must obtain more exact in- 



• See L. and E. Phil. Mag., vol. xii. p. 2G1. | See vol. xiii. p. 329. 



