1848.] PRESTWICH ON STRATA OF CHRISTCHURCH HARBOUR. 43 



of the past, more precious than any hitherto obtained, remain to 

 reward the labours of future observers. I would also remark, that 

 the fact of so long a period as nearly thirty years having elapsed be- 

 tween the first discovery of detached teeth, and of a portion of the jaw 

 of an Iguanodon with teeth in place, notwithstanding diligent and 

 constant research, is worthy of especial consideration, as a striking 

 proof of the little reliance that ought to be placed on what is termed 

 negative evidence ; and it suggests the salutary caution, that we should 

 not hastily infer the non-existence of any forms of animated nature in 

 the earlier ages revealed by geology, simply because no vestiges of 

 their organic remains have been detected. 



2. On the Position and General Characters of the Strata exhibited 

 in the Coast Section from Christchurch Harbour to Poole 

 Harbour. By Joseph Prestwich, Jun., Esq., F.G.S. 

 I HAVE on former occasions described the eocene strata of White- 

 cliff Bay and of Alum Bay * . The sections of these two localities show 

 in a remarkable manner the changes there undergone, in the com- 

 paratively short distance of twenty miles, by the series of sands and 

 clays forming the Bracklesham Bay beds, and included between the 

 London clay and the Barton clay. I also gave the commencement 

 of the section of the Barton clays at Barton, to show their connection 

 with the upper part of the section at Alum Bay. I have recently 

 had the opportunity of further examining the coast-sections from 

 Barton Cliff to Poole Harbour, with a view to continue the sequence 

 of superposition lower in this more westward portion of the series. 

 This part of the coast was described by Sir Charles Lyell in a paper 

 read before this Society in March 1826. I need not therefore enter 

 into a detailed description of the strata, but will confine myself to the 

 question of the exact position which they bear with reference to the 

 Barton clay, and to a few general observations on their physical con- 

 ditions. The progress made by the sea in the destruction of the 

 clifFs has also, 1 believe, brought to light some new features. 



In the first place I have, 1 think, obtained evidence of the exist- 

 ence of the Barton clays to the westward of Christchurch Harbour ; 

 consequently the section downwards from them, which I had discon- 

 tinued at Muddiford, can now be taken up and continued uninter- 

 ruptedly to Poole Harbour. 



Mr. Webster and Sir Charles Lyell have both noticed the sands 

 which underlie the Barton clays at the end of the Barton Cliff near 

 Muddiford. After leaving this cliff, Christchurch Harbour, with its 

 dunes, intervenes for the space of a mile and a half before we reach 

 the cliff at Hengistbury Head. The relation of the strata at this 

 point to those of the Barton cliffs is thereby obscured, and the se- 

 quence rendered apparently incomplete. 



It may be necessary here again to mention briefly the general cha- 

 racters of the lower part of the Barton clays as exhibited in the cliff 

 east of Muddiford. The extreme abundance of fossils in the upper 

 * Quart. Journ. Geol. Soc. vol. ii. p. 224, and vol. iii. p. 408. 



