The cave-deposits have a wider distribution than those which have just been noticed, being also found to the north-west of the above-mentioned line in Yorkshire, and in North and South Wales. In the south of England they are found as far east as Ightham in Kent, and in a westerly direction to Torquay and Tenby. The Ightham deposits occur in fissures and consist of materials which were apparently introduced from above by river action[113]. The cave-deposits of limestone areas are sometimes found in fissures, but at other times in caverns with a fairly horizontal floor, on which the various accumulations lie in order of formation. The deposits vary in character and may be divided into three groups, though accumulations of intermediate character are found; the first group consists of cave-earths and cave-breccias--formed by weathering of the limestone, and the retention of the insoluble residue, as a more or less ferruginous mud, mixed with angular fragments of limestone, and with the remains of creatures which inhabited the caves; the second group consists of true deposits laid down under water, as gravels, sands, and laminated clays; while the third is composed of limestone deposited from solution in water, in the form of stalagmite[114]. [Footnote 113: The Ightham fissures and their contents are described by Messrs Abbot and Newton, _Quart. Journ. Geol. Soc._, vol. L. pp. 171 and 188.] [Footnote 114: The reader should consult Prof. W. Boyd Dawkins' works on _Cave Hunting_ and _Early Man in Britain_, for information concerning the Cave Deposits. See also Sir C. Lyell, _Antiquity of Man_; Sir J. Evans, _Ancient Stone Implements of Great Britain_, and Sir J. Lubbock, _Prehistoric Times_. In these works references will be found to papers by Messrs Pengelly, Magens Mello, Tiddeman and others on the Caves of Devon, Derbyshire and Yorkshire. References have already been made to papers upon the Caverns of North Wales.] The organic contents of the Palæolithic period are of much interest, and it is desirable to discuss their character before making further observations upon the physical conditions of the period.