It is, after all, the succession of varied faunas which really gives students of the rocks the most convincing proof of the vast periods of geological time. If anyone doubts this assertion, let him consider what impression would be made upon him by observing the several thousand feet of strata of the column if none of them contained any organisms. Cognisant as he is of the slow rate of change of existing organisms, the fact that fauna has succeeded fauna in past times brings home to him in an unmistakeable manner the great antiquity of the earliest fossiliferous rocks, and as our detailed knowledge of these faunas increases the impression of great lapse of time is intensified. And if the earliest fossiliferous rocks be of such vast antiquity, and, as has been remarked, the period of their formation is comparatively recent with reference to the actual commencement of earth-history, the latter must indeed be inconceivably remote, and numerical estimates can do but little to familiarise us with the significance of the vast time which has rolled by since the world's birthday. INDEX. Abraum salts, 212 Æolian rocks, 24, 99, 100 Age, definition of, 60 Albian series, 236, 238 Algonkian rocks, 144 Ampthill clay, 232 Angelin, N. P., 161, 162, 165 Aptian series, 236, 237 Aqueous rocks, 24 Archæan rocks, 132 Ardmillan series, 170 Ardwick stage, 192 Arenaceous rocks, 29 Arvonian rocks, 141 Asaphus fauna, 165 Ashgill series, 164, 165, 167-169 Ashprington series, 184 Astian series, 256 Atlantis, 283 Aveline, W. T., 164 Aymestry limestone, 175, 176 Bagshot beds, 244, 246 Bajocian series, 227, 231 Bala limestone, 167 Bala series, 164 Barr series, 170 Barrande, J., 53, 55, 159, 161, 163 Barrois, C., 239 Barrow, G., 138 Barton beds, 244 Bath oolites, 226 Bathonian series, 227, 231 Bed, 27 Bedding plane, 27 Bell, A., 257 Belt, T., 153, 162 Bembridge beds, 251 Bertrand, M., 87, 286 Birkhill shales, 177 Black Jura, 226 Blake, J. F., 138-140 Blanford, W. T., 206, 208, 217, 282, 284 Bonney, T. G., 76, 141, 142 Boulder clay, 262 Bracklesham beds, 244 Bradford clay, 230 Break, palæontological, 61; physical, 60 Bristow, H., 239 Brockram, 211 Brögger, W. C., 161-163 Brongniart, H., 18 Brongniart, C., 200 Bronze age, 275-277 Brown Jura, 226 Bunter sandstone, 218, 220-222 Bure valley beds, 256 Buttery clay, 276