Note on a

Large Boulder found at Branksome,

Upper Parkstone.

By the Rev. H. SHAEN SOLLY, M.A.

EARLY

ARLY in June, 1909, while a sewer was being constructed in Ashley-road, Upper Parkstone, a large boulder was discovered 8 or 10ft. below the surface. It was noticed at the side of the road by Mr. Le Jeune, close to Scott's woodyard, near the bottom of the dip not far from the top of Constitution Hill. It was subsequently presented by Mr. Budden, the contractor, to the Museum of the Branksome Free Library, and now reposes safely in the grounds of that Institution. Its present length is 3ft. 4in., and its greatest girth 4ft. 6in., with a weight of at least half a ton. Originally, its size and weight must have been somewhat more, especially as some portion of it was broken off before it was raised to the surface. The interest attaching to it concerns the question-How came it to be deposited where it was found? It lay in the bed of Plateau gravel which here overlies the Bagshot Sands. The

running water which deposited this gravel was not capable of transporting this block, weighing half a ton. Is there any agent other than ice capable of having done this work, and is the presence of the boulder evidence of a glaciation of Dorset? We may at once dismiss an explanation somewhat recklessly advanced, namely, that the stone was buried by human agency. The soil above it was evidently undisturbed and has never been cultivated, and to suppose that anyone would dig a hole 8ft. deep to bury a stone beneath Ashley Road is absurd. But we may ask, is it not possible that the stone lay on the top of the Bagshot sands, and was there buried beneath the Plateau gravel? I have not been able to ascertain the depth of the gravel at this point, or whether any exists under as well as over where the boulder lay. This question could easily have been answered at the time of the excavation; but inquiries made of the workmen later elicited no trustworthy information. All we can now do is to ascertain the nature of the stone itself. Is it a sarsen, or greywether, similar to the other sarsens derived from Tertiary rocks and widely scattered over the Downs of Wilts and Dorset, or is there no source in the neighbourhood from which it can have been derived, so that it must have been brought from further afield, and may fairly claim the title of an erratic? These questions are not easy to answer. Sections of the stone have been prepared for microscopic examination by Dr. H. Colley March, who has also had slides made, for purposes of comparison, from a typical sarsen lying in the Valley of Stones, near Bridehead.* They

*Photographs of these slides, enlarged 22 diameters, have been kindly made by Dr. Flett, and are here reproduced. An interesting feature in the Branksome slide is that the rock contains many small grains of brown tourmaline, some of which are large enough to be seen with a pocket lens. 1. Bridehead sarsen, photo with crossed Nicols.

2. Same, in ordinary light.

3. Branksome boulder, photo with crossed Nicols.

4. Same, in ordinary light.