[Introductory Note.—After the publication of my paper on the Sarsens, or Sarsen Stones, in the Wiltshire Archæological and Natural History Society's Magazine, vol. xxiii (1886), pp. 122–154, many friendly communications gave me further information on the subject, and additional references to published facts and opinions. From this correspondence, and my own notes made in the country, I propose to utilize much that seems to be of interest. The most important of these additions to our knowledge of the Sarsens is the following memoir on their constitution and structure by my friend Prof. Dr. J. W. Judd, C.B., F.R.S., etc., of the Royal College of Science, who most obligingly examined with care the microscopical structure of many specimens from authenticated localities. With his kind permission this valuable communication (dated March 9th, 1888) is here printed.—T. RupertJones.]

When searching for traces of the dermal structure preserved in the specimen of Hyperodapedon in the British Museum (Natural History) in London, my attention was drawn to certain spots where the matrix showed projections and pits of a polygonal shape, which I detected when I took the photographs of this Triassic reptile. Primarily occupying myself with the matrix of the principal slab, in which the skeleton is enclosed, I quite thought I had only to deal with dermal structures similar to those discovered in Rhynchosaurus.

There are three specimens of this species in the Woodwardian Museum, viz.: (1) Salter's fine original specimen (a 954) from the Wenlock Shale of Malvern, belonging to the first part of the Fletcher Collection, acquired prior to 1873; (2) a poor specimen probably from the same collection and horizon, locality unknown; and (3) an almost perfect specimen, also from the Wenlock Shale of Malvern, belonging to that part of the Fletcher Collection recently presented by Mrs. Fletcher. This specimen will be designated the Fletcher specimen in distinction to Salter's original specimen. Both these specimens show almost the whole trilobite preserved in excellent condition, and from them the following description has been drawn up.

Last February, while working in the Chemical Laboratory of University College, London, I had occasion to make some sulphanilic acid. This was done in the usual way by heating a mixture of 100 grammes of concentrated sulphuric acid and 30 grammes of aniline to 180°–190° C. in an oil bath for four hours. The flask containing the mixture was left in the oil bath to cool, and on examining it the next day I was surprised to find that the solid mass inside had developed a beautiful spherulitic structure. As I believe this has never been observed before, it may be worth a description.

About ten years ago, when studying the drifts of East Yorkshire, Mr. G. W. Lamplugh counted and roughly classified the larger boulders of Flamborough Head and other selected localities on the coast. This work has been continued by members of the Hull Geological Society, who have up to the present time recorded nearly four thousand boulders, of twelve inches and upwards in diameter. To avoid possible error, arising from the moving beach and other causes, only the boulders actually in place in the clay were noted, or such as had obviously recently fallen from the cliffs. The whole of the coastline from Spurn to Flamborough has been surveyed in this way, and also portions of the coast north of Flamborough as far as Saltburn. The lists thus prepared have been published from time to time by the Hull Geological Society and by the Erratic Blocks Committee of the British Association.

At the meeting of the British Association at Newcastle in 1889. I brought out my interpretation of the probable origin of the limestone knolls of Yorkshire.