1 40 Mr. H Atch et j V Qbfervations on Bituminous Subjlances. 



lection, exhibit the concentric circles of their annual growth, with 

 this difference, that the trunks have been fo compreffed as to be 

 nearly flat, fo that the circles appear like parallel lines connected 

 at their extremities hv a ihort curve. 



I did not obferve Inch an appearance at Bovey ; but this would 

 depend upon the pofition of the trunks of the trees, in refpect to 

 the lection of the ftrata. 



Chaptal*, Troilf, Bergman J, and many others, have been of 

 opinion that the furturbrand is wood which has been charred by 

 the heat of the lava. But I cannot difcern why it fhould be fup- 

 pofed that it has been acted upon by fire, any more than that the 

 Bovey coal has been fubjeeted to the effects of the fame agent. 

 The qualities of the two fubftances are the fame; and as (from Arch- 

 bifhop Troil's and ProfeiTor Bergman's account) the furturbrand is 

 itratihed, I think we may venture to pronounce that the circum- 



fiances 



* Eleuiein's of Ckeiniflry, vol. iii. p. 199. 

 I Von Troil's Letters j p. 43. 



% Quid de ligno foffili Iflandiae fentiendum fit, gnaro in loco natali contemplatori 

 (kcidendum relinquimus. Interea, ut cum Vulcani operationibus nexum credamua, plure* 

 iuadent rationes, quamvis hue ufque modum ignoremus, quo fitum texturamque ad- 

 quifiverunt hxc ftrata. Scilicet truncis arborum perquam craflis conftant, qualis in 

 Jflandia nullibi reperiuntur, et ne quidem hoc tempore crefcere pofle videntur Hi fitu 

 horizontal! in flratis multorum pedum craflitiei congefti funt et petroleo plus minus 

 penetrati, non jam molli, fed optime indurato, a quo tarn nigrorem, quam flammai fub 

 rlefiagratione qualitatem mutuantur. Sed quod in primis attentionem tneretur, eft 

 truncorum in lamellas planas compreflio. 



Ponamus truncum arboris cujufdam -tranfverfim fectum, nine, uti notum eft, figura 

 oritur in orbem rediens circiter circulars, quae omnia monflrat annotina increments, 

 rxtimo propemodum parallela. Fingamus jam talem fedionem in tenuem laminam com- 

 prefTam, et veram habebimus ligni foffilis, de quo heic agitur, ideam ; nam in magmV 

 hujus materia fruRis, tranfverfim feflis, quemlibet annotinorum orbium vifu perfequi 

 Jicet, ita plerumque coaSum, ut duas lineas fere parallelas exhibeat, quarum extrema 



brev] 



