730 PHILOSOPHICAL TRANSACTIONS. [aNNO 1743. 



the breadth not above a quarter of a mile ; and depth, at a mean computation, 

 about 5 feet. It is used in manure for the same purposes as chalk is, but 

 answers the intent much better. It rises up in one continued bed, almost to 

 the surface ; where a thin layer of common earth but just hides it in places, 

 where continual cultivation has not superinduced a new soil. The whole bed 

 consists of separate detached pieces, and of several dimensions, mostly long 

 and tubular ; some few round, with a small cavity in the centre, others quite 

 flat, and some, as it were, excavated on one side, as if the chalky laminas had 

 extended themselves round a piece of bark ; but all of them hollowed within, 

 agreeable to their exterior shape, very few excepted. 



This valley formerly was probably over-run with wood, if not wholly, at least 

 for some considerable length and breadth : wild boars tusks, which are known 

 by their length ; stags-horns, and a flint-knife, which have been found buried 

 to some depth, in the malm, seem to evince as much. That trees of con- 

 siderable dimensions have grown in it, is very evident ; for, in a drain, lately 

 made to convey the water from the main river to the adjacent meadows, trees 

 of a vast size may be seen, at 2 or 3 feet depth, in no small number, retaining 

 both shape and substance in some measure, though much decayed, and not so 

 compact and solid in those parts, which have been exposed to the water ; these 

 lie out of the verge of this bed of malm, and are not consequently affected 

 by it. 



Now probably these trees, with the rest of the wood, might, by age, and 

 some accident combining with it, have fallen; the uppermost might have served 

 to bury the rest, and preserve them from a more immediate decay, by cutting 

 ofF their communication with the exterior air. Rains, in process of time, must 

 have washed oflT from the adjacent hills to some certain distance, and deposited 

 in the neighbouring valley, but mixed with other heterogeneous substances, as 

 decayed wood, earth, &c. a quantity of chalky particles, sufficient to involve, 

 by a continual addition of new laminae, roots, trunks, branches, twigs, and 

 the broken extremities of twigs ; and tending continually to form masses re- 

 sembling the supposed particulars. He supposes, that the pieces of wood have 

 been invested continually by additional laminae; that the first laminae must have 

 adapted itself to, and assumed the exterior shape, whether smooth or knotty, of 

 the inclosed wood ; that the others have proceeded accordingly ; that the ex- 

 tremities have gradually rounded themselves ; and that in the interim, till they 

 were wholly closed, the included wood has been insensibly attenuated by the 

 passing moisture, and, particle by particle, either entirely, or in part only, 

 wasted away. And though it may be objected against this supposition, that 

 some pieces are entirely solid, and have the resemblance of white-thorn ; yet 



