the Bolton Bailwat/, at Dixon Fold, neur Manchester, 161 



ration between them would be more or less clearly defined as 

 the change was gradual or sudden. It is obvious that if the 

 tree had been originally hollow and of uniform diameter, the 

 sediment introduced would correspond, both in quality and 

 thickness, with that on the same level around it. If, on the 

 contrary, it had been solid, no sediment, while it continued 

 so, could be admitted ; but if, in process of time, it became 

 hollow by decay, it would then be in a condition to receive 

 wliatever sediment the water might at the time be depositing, 

 it being borne in mind that it was submerged, standing erect, 

 or nearly so, with its lower portion buried up by the deposits 

 that had been accumulating round it while solid. In the 

 latter ca.se, the strata on the same level, within and around 

 the trunk, would not correspond, but the introduced matter 

 would resemble the beds of which it was the equivalent. 



I will now briefly describe the actual conditions of the tree 

 No. 1, and of the surrounding strata, and then see how far 

 they can be reconciled with the above theory. This trunk is 

 a compact fine-grained sandstone, with an intermediate hori- 

 zontal band of shale nine or ten inches thick, the bottom of 

 which is two feet above the present base, and which separates 

 the sandstone into two distinct beds. This band is distinguish- 

 able from pure argillaceous shale by a mixture of sand ; and 

 where weathered, is seen to consist of a number of very thin 

 plates of soft bluish sandstone with intermediate laminae of 

 shale. It is separated from the contiguous sandstone, both 

 above and below it, by an abrupt and definite line, indicative 

 of sudden changes in the nature of the deposit, which changes 

 are the more remarkable, because, in the coal-measures, the 

 transition from one deposit to another is generally gradual 

 and indefinite. The matrix that envelopes the lower half of 

 the tree and lies upon the nine-inch seam of coal, is a grey 

 argillaceous shale, that imperceptibly changes upwards into a 

 sandstone not distinguishable fro;n that which forms the tree 

 itself. On a cursory view this sandstone appears to be some 

 yards thick, but on removing its pai'tial covering, a well-defined 

 bed of laminated shale may be seen inserted. Above the 

 sandstone other deposits succeed which it is not necessary 

 here to notice. On comparing the deposits within the trea 



VOL, XXXI. NO. LXI. — JULY 1841. L 



