STRATA OF THE HAMPSHIRE BASIN. 175 



testimony, movements which brouglit about those terrestrial condi- 

 tions that prevailed over so large an area in Miocene times. Of these 

 great movements we are not without illustrations in this country ; 

 for striking evidences of them are afforded in the folded, uptilted, 

 and occasionally inverted strata of the Hampshire basin. 



When it is further remembered that the classification of the 

 fluvio-marine strata in our Hampshire basin has always presented 

 peculiar difiiculties to geologists, and that for a long time no course 

 seemed open to them between unnaturally extending the bounds of 

 the Eocene so as to embrace them, or else of breaking up this ho- 

 mogeneous mass of deposits and placing one part in the Eocene and 

 the other part in the Miocene, I think we may assert of any method 

 which avoids both of these inconvenient arrangements that it is worthy 

 of the most serious attention ; and if I have not been altogether 

 unsuccessful in the manner in which I have presented the subject, 

 the exact agreement of our Hampshire fluvio-marine strata with 

 the lower divisions of the continental Oligocene must be clearly ap- 

 parent to everyone. 



It is of course a matter of comparative indifference to geologists 

 whether they classify the Cainozoic deposits in three or four great 

 groups ; but I maintain that the thickness of the strata and the di- 

 stinctness of the fauna and flora of the Oligocene are such as to 

 entitle it to take rank as a great system by itself, and that this is a 

 more natural arrangement than to group it either with the Eocene 

 or Miocene, or to divide it between those two systems of strata. 



It is no answer to this argument to assert that beds are found 

 forming a complete transition from the Eocene to the Oligocene, and 

 others which bridge over the gap between the latter and the Miocene. 

 As our acquaintance with the geological series grows over widening 

 areas, such transition deposits will constantly be discovered. Eew 

 will be bold enough to assert that because we find in the Vienna 

 basin a continuous series through the Miocene into the Pliocene, 

 therefore these two great divisions ought to be given up : for on 

 such grounds every possible classification and terminology of geolo- 

 gical deposits would have to be abandoned. I argue for the use of 

 the term Oligocene in this country because its convenience has been 

 felt and demonstrated over a large part of the continent, and be- 

 cause it enables us to get rid of serious difficulties connected with 

 the classification of a very important part of our British series of 

 strata. 



EXPLANATION OF PLATE VII. 



In fig. 1 is given a facsimile of the diagram published in Forbes's ' Tertiary 

 Fluvio-marine Formation of the Isle of Wight,' p. 89. In this section no 

 attempt has been made to maintain the relative proportions between the heights 

 of the several cliffs ; and hence several serious errors are conmiitted in joining 

 the different strata by means of dotted lines. The Headon-IIill sands are 

 represented as occupying not only the whole base of Headon Hill itself, but as 

 being largely developed in Totland Bay. Yet a carefid examination of the 

 section will show that this view is quite erroneous. As the Ileadon-IIill sands 

 are 70 feet beneath the marine band (Middle Headon), we ought, if Forbes's 

 view of the identity of the Colwell-Bay and the Headon-Hill marine beds be 

 the correct one, to find them in Totland Bay ; for there are 120 feet of strata 



