ANNIVERSARY ADDRESS OF THE PRESIDENT. 



CI 



If we compare again the proportions of the several English sections 

 with those of the French, we find the per-centage thus — 



Loudon Clay, 



16. 



Lits Coquilliers, 



25. 



Bracklesham Sands, 



51. 



Calcaire Grossier, 



42. 



Barton Clay, 



37. 



Sables Moyens, 



33. 



And although, the Lits Coquilliers and the London Clay are not 

 exactly in the same relative position in these comparisons, it must 

 be admitted that the indirect evidence afforded by the Bruxellian 

 series is strongly in favour of the next step of correlation, namely, 

 the identification as a synchronous deposit of the Barton Clay with 

 the Sables Moyens. This question is indeed worked out with great 

 care, not only by a reference to the proportion of Barton species 

 found in the several sections of the English and French Lower Ter- 

 tiaries, but also by another species of comparison which is at once 

 natural and philosophical, namely, that of the variation upwards in 

 each distinct basin or organic region : — 



IN THE ENGLISH. 



Barton 30 



Bracklesham 100 



IN THE FRENCH. 



Sables Moyens 35 



Calcaire Grossier 1 00 



or taking the per-centage in a downward direction- 



Barton 100 



Bracklesham 45 



Sables Moyens 100 



Calcaire Grossier 50 



so that this portion of the question seems most satisfactorily an- 

 swered, although it had difficulties of no ordinary kind in its way. 

 The next question is, whether the Laeken beds, or those above the 

 Bruxellian, should be classed with the Sables Moyens, as the cor- 

 relation of the Bruxellian with the Bracklesham would appear to 

 imply ; and this, though Mr. Prestwich gives strong reasons in favour 

 of the correlation, he leaves open for future discussion. Taking, how- 

 ever, the proportion he has adduced in an ascending order, in respect 

 to the species as follows, — 



Laeken Beds 27 



Brussels Beds 100 



Barton 30 



Bracklesham 1 00 



and combining it with the fact of positive superposition, I think the 

 probability is greatly in favour of the correlation of the Laeken 

 Beds, Barton Clay, and Sables Moyens. I will not attempt to give 

 here an analysis of Mr. Prestwich' s reasonings in respect to the 

 physical relations of the several basins to each other, such as the 

 progressive approximation in mineral character as the French series 

 ranges towards the English area ; or the difference in the floras, 

 which appears to imply that whilst there was a sea connexion be- 

 tween the basins, the land areas were different or disconnected ; they 

 can be only satisfactorily followed in a patient perusal of the paper 

 itself, and I will therefore merely add, that in the preparation of the 

 lists of fossils, and in the careful digest of the evidence they afford, 

 Mr. Prestwich has fully maintained his position in this most difficult 

 branch of geological science. 



