r ( r„j THE GEOLOGIST. 



NOTES AND QUERIES. 



Pisstjiies Portland Strata. — In your review of the proceedings of 

 the Geologists' Association, in your last November number, you have noticed 

 some remarks of Mr. Gray on the bone fissures in the Isle of Portland. I do 

 not think you have quite caught the meaning he intended to convey. 



The Island of Portland consists of a base of Kimmeridge clay, covered by 

 by strata of Portland sand and Portland oolite, and capped in some parts of 

 the Island by a few feet of calcareous slate belonging to the lower Purbeck. 

 Pissures occur in the oolite, caused apparently by the shrinking of the stone 

 in the act of consolidation. There is an excellent woodcut representing one 

 of these fissures in Mr. Damon's " Geology of Weymouth and the Isle of 

 Portland," page 73. It will there be seen that the fissure affects all the beds 

 beneath the dirt bed, as far as the sand. Now, the facts that the roots of the trees 

 which grew in the dirt bed penetrated the stone beneath, and that the calcareous 

 slate was deposited around the stumps of those trees before pctrefaction, show 

 that the slate was deposited before the stone was _ consolidated. The subse- 

 quent shrinking of the stone, which is pale, crystalline, and rings beneath the 

 hammer, seems to have caused the fissures in the stone beds that do not pass 

 upwards into the calcareous slate. Not that the slate has not likewise con- 

 tracted in hardening, but its contraction has caused a multitude of small in- 

 terstices at short intervals, whilst the insterstices between the blocks of solid 

 stone have occurred at greater distances from each other, and, therefore, taken 

 singly, are of greater width, and have 

 no corresponding fissures above them 

 on the slate. Now, what Mr. Gray 

 means with respect to the human 

 bones, which have been occasionally 

 found in the fissures, is this — viz., 

 that they have only been found in 

 those parts of the Island which are 

 capped by the calcareous slate, and 

 not where the stone is immediately 

 subjacent to the vegetable soil. 



Prom what you have quoted from his paper, I would conclude that, where 

 this is the case, the fissures are not vacant, as in the other parts of the Island, 

 but filled with rubble from above, and, therefore, parts of skeletons interred 

 above them would not fall down into them. 



Mr. Damon has expressed the same opiuion as Mr. Gray — that the human 

 bones in these fissures have fallen from graves in the soil above. He says 

 they " are interred remains, and found a few feet beneath the surface in the 

 rubble bed (that is the calcareous slate), though a stray bone or two may 

 find its way down a fissure where the bones of these animals may have been 

 deposited." (p. 130). 



Of course this does no more at the most than show that no fossil remains 

 of man have hitherto been found in Portland, but in no respect affects the 

 (Mies lion — whether or not they have been found elsewhere ? 



There are some curious questions connected with the occurrence of mam- 

 malian bones of fissures iii small islands like Portland and the Isle of Caldy- 



