336 Correspondence — Mr. Jiihcs-Broicne. 



is of the highest importance. Clearly the degree of probability 

 ought not to be exaggerated. But precision is in itself no such 

 exaggeration. 



The very necessity of stating an opinion precisely and definitely, 

 if at all, and of making it correspond throughout with all the surface 

 facts so far as they have been observed, is a great incentive to care- 

 ful thoroughness ; and the work specially required for underground 

 contours, both in the field and in the office, gives much more than 

 ordinary value to a geological survey. 



He asks further : " Whether I would advise the use of distinct 

 plans on which to record the positions of the contours at the various 

 depths, when ascertained." Of course the various depths can have 

 each but one contour line, and naturally I would not recommend 

 a separate map for every contour line ; but perhaps some misprint 

 or otber slip has concealed the drift of the question. 



Northampton, Mass., 20 May, 1885. Benj. Smith Ltman. 



THE CLASSIFICATION OF THE JURASSIC SYSTEM. 



SiK, — I had not intended to trouble you with any further remarks 

 on this subject, but as part of Dr. Blanford's last letter has been 

 repeated in the June Number of the Magazine for the sake of cor- 

 recting a typographical error, I may be allowed to answer the 

 paragraph so reprinted. 



I think Dr. Blanford fails to apprehend the object of my reference 

 to the Lower Calcareous Grit. It was this, — he proposes to place 

 the Coral Rag in the upper division and the Oxford Clay in the 

 middle division of the Jurassic system ; I reply that the lower 

 member of the Coral Kag is so closely connected by its fossils with 

 the Oxford Clay, that it would be unphilosophical to draw such an 

 important line of separation below it. 



I do not see what the Callovian has to do with this argument, but 

 I had certainly not forgotten its existence, for I happened to mention 

 it in my first letter (Geol. Mag. 1884, p. 525) as forming the base 

 of the Oxfordian. 



My argument is simply this, that there is a greater palseontological 

 change in passing from the Cornbrash to the Oxfordian than there is 

 between the Oxfordian and the Coral Eag. The question of the 

 lithological change is not worth further discussion ; I quite admit 

 that the point should be decided on palseontological grounds, but I 

 do not agree with Dr. Blanford's method of handling the facts. 



June %lh, l^ib. A. J. Jukes-BrOWNE. 



The Dakwin Memorial Statue, the execution of which, in white 

 marble, had been entrusted to Mr. Boehm, was unveiled by H. R. H. the Prmce of 

 Wales at the British Museum (Natural History), Cromwell Road, ou Tuesday, 

 9th June, 18^5, when Prof. Huxley, President of the Royal Society, delivered an 

 address on behalf of the Darwin Memorial Committee, and handed over the care of 

 the statue to the Trustees. The Prince of Wales replied on their behalf. The 

 Archbishop of Canterbury and many other of the Trustees were present, and a large 

 assemblage of scientific men and friends and admirers of Darwin filled the Great Hail. 



