VOt. LI.] PHILOSOPHICAL TRANSACTIONS. 44] 



trees; the laminae, which have the appearance of Wood, being always horizontal, 

 according to the situation of the pieces in the strata: or could we suppose a 

 number of fossil trees to be brought together, and ranged in this regular manner 

 in the severol strata, yet by the form and roundness of their trunks, they must 

 be in a great measure encompassed by the soil, in which they are buried; where- 

 as there is not the least mixture of earth, or any other aperture in the Bovey 

 strata of coal, except a few crevices, common to this sort of fossil, which divide 

 the pieces from each other in all directions, and seem to be inconsistent with the 

 nature and fibrous texture of wood. If the basis or matrix of this fossil were 

 wood, it would acquire, by being impregnated with bitumen, a greater degree of 

 inflammability; whereas it neither kindles nor consumes so fast as wood. 



Dr. M. mentions a number of other places where such fossil substances are ' 

 found; and then concludes with observing the several particulars in which all 

 the species of the bituminous fossils resemble each other. They seem to be 

 generally found between beds of clay or stone; are of a dark brown, or black 

 colour, of a laminated texture ; pliable when moist, and fresh dug, but crisp 

 and brittle when dry; full of cracks, and easily breaking transversely; thev all 

 sink in water, and emit the same nauseous and bituminous smell; they differ in 

 being more or less solid, heavy, and inflammable, according to the proportions 

 and principles of which they consist; and if any doubt could remain of their 

 being a mineral substance, it must be removed by the following analysis. One 

 pound of Bovey coal, of the woody kind, powdered, put into a glass retort, and 

 distilled in sand, yielded 4i-oz. of phlegm, which had the appearance of com- 

 mon water, but somewhat of a bituminous smell and taste ; near 4 oz. of a 

 turbid whitish bituminous liquor, of an intolerable fetid smell, and extremely 

 pungent to the tongue; about 2 drs. of a heavy bituminous matter, which would 

 not mix with the liquor above mentioned, but sunk entirely to the bottom, and 

 (which is very remarkable) there was not the least appearance of any light oil 

 floating on the bituminous liquor. There remained in the retort about 7 oz. of 

 a very black powder, which had the same bituminous smell, not very heavy ; 

 some of which being put on a red-hot iron, emitted a little smoke, but no flame. 

 The ashes of this fossil, when burnt, being boiled in water, and the water eva- 

 porated, there remained no salt behind. 



LIF. A New Method of Computing the Sums of Certain Series. By Mr, 

 John Landen. Communicated by Mr. Thomas Simpson, F. R. S. p. 553. 



1. Supposing JO to be the sine of the circular arc z, whose radius is 1, 



--^-. will be = i: and consequently, —Ar= = -^=r. Hence, by taking the 



X + a/x^ 1 z 



con-ect fluents, we have hyp. loa;. ;=:: = . — . 



■" *=■ V — 1 V — 1 



VOL. XI. P L 



