64 WILLIAM LONSDALE. [1847-48. 



Barton, &c., was wrong, and that instead of being of the 

 age of the Calcaire Grassier, they were of older date. 



An interesting letter to Mr W. Lonsdale, formerly 

 the esteemed Curator and Librarian of the Geological 

 Society, evidently refers to those two papers : 



20 MARK LANE, LONDON, 21st Dec. 1847. 



MY DEAR SIR, You may probably not recollect the circum- 

 stance of my bringing you, in the year 1839, a paper on some 

 detached portions of the Tertiary series of the neighbourhood 

 of London. The facts were incomplete, and did not possess 

 much novelty. After reading the paper, you recommended me 

 not to present it to the Society at that time, and suggested a 

 further examination of the ground. At the same time you 

 expressed a regret that the English Tertiaries had not met 

 with the attention which the French Tertiaries had. 



With a full conviction of the correctness of your opinion, 

 I looked further into the state of our knowledge respecting the 

 English Tertiaries, and endeavoured to make myself better 

 acquainted with their structure. From 1839 to the present 

 date I have continued without interruption at my limited leisure 

 moments the work which I then thought would require but 

 a few weeks, and have still, I find, much to do. On portions 

 of the subject I have, after a careful examination of the district, 

 been led to form different views [from] those held generally, 

 and these I have now in 1847 communicated to the Geological 

 Society. It gives me now, I can assure you, much pleasure to 

 hand you for your kind acceptance a copy of my papers pub- 

 lished in the last number of the Journal. If there is any merit 

 in them, to you in a great measure do I attribute such a result. 

 It was at your suggestion that I proceeded in the work, and it 

 has been the cautious and philosophical spirit of careful in- 

 vestigation and comparison of facts which I so frequently 

 experienced in you that has helped to guide me through it. 

 With my best and sincere wishes for your health and welfare, 

 and with a grateful recollection of your frequent kind advice 

 and assistance in many a geological difficulty, I remain, my dear 

 sir, very sincerely yours, J. PRESTWICH, Jr. 



