90 



KNOWLEDGE 



[April 1, 1895. 



differences between the various forms ; they will, in fact, 

 be initiated into the ways of true naturalists, for science is 

 made up of the accumulation of facts and the illscussion 

 of their relation to one another. This both instructs in a 

 definite line of work fairly easy to follow, and while it will 

 certainly develop interest in microscopic aquatic life, it 

 may also help in the education of scientific investigators. 

 A chapter on the management of the micro-aquarium 

 shows the student how to stock and study the objects he 

 collects. 



BOOKS RECEIVED. 



Fust Year of ficieiitifio Knoirlfdge. Bv Paul Bert. ( Eelf e Bros. ) 

 2s. 6d. 



Mechanics: Theoretical and Practical — Statics. By R. T. 

 Glazebrook. (Cambridge UniTcrsity Press.) 3s. 



Conic Sections treated Oeometricalli). Br W. H. Besaut, D.St-., 

 F.R.S. (Geo. Bell & Sons.) 4s. 6d. 



An Elementarit Text-book of Hydrostatics. By William Briggs. 

 (University Correspondence College Press.) 23. 



The Source and Mode of Solaf lUnergy throvghout the Vnirerse. 

 By I. W. Heysinger. (Lippincott.) Illustrated. 



The Story of the Stars, simply told for Gt neral Readers. By 

 C. F. Chambers. (Xewnes.) Illustrated. Is. 



The Astrologer s Ready Reckoner. By C. J. Barker. (Occult 

 Book Company, Halifax, U.S.A.) 3s. 6d. net. F( r ascertaining the 

 approximate zodiacal position of the sun, moon, and stars. AVith 

 tables showing the time of the sun's return to a given position in the 

 zodiac for the erection of revolutionary or solar figures. 



Bibliogrnjihy of Aceio Acetic Ester and its derivatives. By Paul 

 II. Seymour. (Smithsonian Institute.) 



The Tarietiei of the Human Speciei. By Guiseppc Sergi. 

 (Smithsonian Institute.) 



Popular Phrenology. By Prof. W. Cross. (Iliffe & Son.) Is. 



A Student's Te.vt-hook of Sotani/. Bv Sydney H. Tines, M.A,, 

 D.Sc , F.R.S. (Swan, Sonnenschein',S: Co.") 'iSs. 



SUSSEX: ITS GEOLOGICAL STRUCTURE. 



By Prof. J. Logan Lobley, F.G.S., &c. 



SUSSEX geologically may be considered to be a 

 counterpart of Surrey, since it is mainly formed by 

 the southern half of the great anticlinal of which 

 Surrey occupies so large a part of the northern 

 half; while, therefore, their general dip is in an 

 opposite direction, the formations, with one or two excep- 

 tions, are the same in the one county as in the other. 

 The Thanet Sands, the Oldhaven Beds, and the Bagshot 

 Sands of Surrey are absent in Sussex ; but, on the other 

 hand, the more southern county exposes lower beds than 

 any having an outcrop in Sm-rey, for the lowermost 

 members of the Hastings Sands form a large area in 

 Sussex, and the still older Ashburnham Beds, once included 

 in that division of the Wealden series, but now classed with 

 the Pm-becks, are at the surface near Hastings and Battle. 

 As the main Wealden anticlinal axis extends east and 

 west, not far distant from the north side of the county, the 

 dip of the formations of Sussex generally is towards the 

 south. The beds of the narrow strip of country between 

 the anticlinal axis and the northern boundary, of course, dip 

 to the north, and the central area of the county is so 

 faulted that there is in that district much local diversity of 

 dip. But the feature of Sussex that renders it most con- 

 spicuously different from the quite inland county of Surrey 

 is its long coast-line, which presents a front washed by 

 the English Channel of about 90 miles. Sussex is about 

 78 miles in length from the Hampshire boundary on 

 the west to Kent Ditch on the east, with a somewhat 

 regular breadth, having a maximum of about 27 miles, 



giving a total area of 934,00G to 019,881 acres, which 

 exceeds the area of Surrey by 4-17,807 to l(i3,H42 

 acres. 



The main physical divisions of Sussex, each of distinctly 

 different geological structure, may be stated to be ; — 

 (1) The district at the south-west of the county lying 

 between the South Downs and the sea ; (2 1 the area of 

 the Downs ; (3) the valley along the north foot of the 

 Downs ; (4) the elevated lands at the north-west, and 

 extending southwards and eastwards north of the Downs ; 

 (5) the great Weald Vale ; and (6) the Forest district. 



It will be seen that these correspond very closely with 

 the physical divisions of Surrey, and that a most con- 

 spicuous feature in each county is the Downs area, but 

 there is one important exception, for the Bagshot district 

 of sandy heaths is quite unrepresented in Sussex. 



The Forest district occupies a very large area, since it 

 forms the central portion and the whole of the north- 

 eastern part of the county. It extends along the ridge 

 and on both sides of the main Wealden anticlinal, and 

 consists of elevated land, varied with numerous small and 

 some considerable valleys, and attains at Crowborough 

 Beacon, in Ashdown Forest, an elevation of 79(3 feet 

 above Ordnance Datum. It is a richly wooded district, 

 which, with its diversity of surface, gives great picturesque- 

 ness, with, in some areas, much wildness of aspect. St. 

 Leonard's Forest, Tilgate Forest, Worth Forest, Balcombe 

 Forest, and Ashdown Forest, cover very large areas of 

 the highest ground, while many beautiful parks adorn the 

 slopes and valleys, including the grandly timbered Bridge 

 Park, the oldest deer-park in England. The forest ridge, 

 extending to the sea, gives the lofty cliffs from Hastings to 

 Fairlight Head, which at the coastguard station rise to 

 478 feet above the level of the sea. 



The whole of this extensive area is formed by the 

 Hastings Sands and the patches of Purbeck beds before 

 mentioned ; the highest levels in Ashdown Forest con- 

 sisting of the lowest division of the sands, the Ashdown 

 Sands. 



A considerable amount of interest attaches to the Purbeck 

 beds of Sussex, since the celebrated Sub-Wealden boring 

 of 1872-74 was carried out in Limekiln Wood, near Battle, 

 on these beds, as the lowest geologically of the whole of the 

 Wealden area. Although, at 1780 feet, Palseozoic rocks 

 with coal were not reached, as expected by some, the 

 results were both of scientific and economic importance, 

 for the true character and position of the Ashburnham 

 beds were determined, the thickness here of the underlying 

 formations ascertained, and valuable beds of gypsum were 

 struck within 140 feet from the surface. 



Dipping at a greater angle than the surface slope, the 

 Ashdown Sands pass under the middle and upper members 

 of the Hastings Sands, which constitute the greater portion 

 of the Forest district, and of this portion the Tunbridge 

 Wells Sands form much the larger area. These are for 

 the most part soft, white sand-rocks, of which the well- 

 known " Piocks " of Tunbridge Wells and Eridge, and the 

 "Toad Eock '' of Rusthall are good examples; but near 

 Cuckfield they furnish a hard building stone, the Tilgate 

 grit, in which Dr. ^lantell's Ljmmodon was first found. 

 It was chiefly from the Wadhurst Clay, between the Ash- 

 down and the Tunbridge Wells Sands, that the ironstone 

 nodules were obtained that furnished the Wealden iron ol 

 the last and preceding centuries. Many names are met with 

 in Sussex that serve as memorials of the old iron industry 

 of the Weald. " iline-pits " may still be found in the 

 woods of the Ashburnham district, and slag-heaps over- 

 grown with vegetation at the sites of the former furnace 

 tires. 



