200 ANNUAL OF SCIENTIFIC DISCOVERY. 



of similar appearanco and analogous propertios to asphaltura 

 fflanee." It is alic^jcd that the theory of coal having been cou- 

 clensed from a liquid, in the same way as this " as])haltum glance," 

 accounts better tlian any other for its purity, seeing that " all 

 impure or foreign substances which did not decom2)osG would 

 most likely be of greater specilic gravity than oil, and conse- 

 quently sink to the bottom." 



The high state of preservation in which plants frequently occur 

 in our coal-beds, and the fact of trees being found erect in them, 

 are easily accounted for upon this theory. Trees grow on the 

 hardened pitch of the Trinidad lake, within a short di.stance of 

 other pitcli in a state of el)ullition, and one can readily conceive 

 of tiie hardened pitch, in any similar case, beting softened by the 

 eruption of the boiling pitch, and of the trees growijig on it being 

 thus ino-Hlfed, or of the lake overtlowing its banks and so sub- 

 merging adjacent vegetation. Tiie new theory also furnishes a 

 simple explanation of the " exceeding minuteness of many coal- 

 seams, which thin out into mere lilaments over extensive ai'cas of 

 solid rock," and might well be due to an oily liquid having over- 

 flowed the rock wlien it was at the surface, and having then, in 

 jjrocess of time, in part evaporated and in part solidified. The 

 shape and dimensions of many other coal-seams are equally con- 

 sistent with the idea of the seams in question being the solid resi- 

 duum of what once were lakes of oil, and indeed the great majority 

 of all the known coal-formations are basin-shajjcd, " witii long 

 and sloping sides dipping down to a common and profound 

 centre ; " a fact which certainly tells with great force in favor of 

 the new hypothesis. On the whole, it must be admitted that the 

 theory that the first step in the formation of coal was the produc- 

 tion of " tan-y oils," by the destructive distillation, at a compara- 

 tively low heat, of vegetable and perhaps animal matter, and 

 that coal consists of the less volatile portions of these oils, solidi- 

 fied and hardened b}' heat and pressure, is not without plausi- 

 bility, at least in respect of certain kinds and formations of coal. 

 There are some coal-beds which present phenomena wliich could 

 scarcely, so far as we can at present see, be accounted for on this 

 theoiy ; but further researches will doubtless throw additional 

 light on the whole matter; and it is not necessary that we should 

 suppose that all the coal that exists was formed precisely iu the 

 same way. — Mechanics' Magazine. 



ORIGIN OF PETROLEUM, 



In " Silliman's Journal," for July, 1866, is an article on "Pe- 

 troleum and its Geological Relations," by Prof. E. B. Andrews, of 

 Marietta, Ohio, from which the following are extracts: "Of the 

 origin of petroleum there are different opinions. All agree, how- 

 ever, that it must ultimately be traced to vegetable or animal sub- 

 stances, the primary combinations of hydrogen and carbon being 

 the product of vital force. It is the opinion of Dr. J. S. Newberry 

 and others that petroleum iu its present form is the product of a 

 felow distillation of bituminous strata. From this theory ili*. T. S. 



