181 



No-w that I have alluded to the sale of one of my books, I may mention 

 to you in confidence, -nhile it is a publishers' secret, that Murray has sold 

 all the copies he has on hand of the 6th Edition of the "Elements;" so that 

 in a year it will be out of print ; and I mean to leave it out of print for 

 another year, hoping, if I live, to give an improved version two years 

 hence. 



My difSculty is that I should like to enlarge it as well as to re-cast parts 

 of it ; but I have received warnings from certain teachers of geology who 

 would like to use my Elements as a text-book that the book is already too 

 bulky, or at least too costly for the purses of their students, and that, how- 

 ever much improved, it wiU sell less if I do not take care to keep down the 

 cost. As they are possibly right, and the first thing is to consider in books 

 of this kind, far more than in treatises such as the " Principles," how to 

 make them useful to great numbers of students, I should be very glad of 

 any hints. 



The public are, no doubt, of the opinion of the old woman at Boston, 

 Massachusetts, whose eyes and purse were growing weaker, and who was 

 purchasing a Bible, and said she wanted one with the largest print and the 

 lowest price. But perhaps something might be done by omissions, and I 

 should be glad of any hints. 



I look upon your discovery of marine fossil shells in the Drift S. of Dublin at 

 the height of 1200 feet above the sea as most important : I believe I have 

 not yet told you so. A good conchologist would do well to hunt up every 

 fragment, and get us a good list of species ; and every additional foot of 

 altitude to which they can be traced is no small gain now thab these theories 

 about the rising and falling of the sea, instead of oscillations of the land, 

 are mooted. 



Believe me, dear Harkness, 



Ever truly yours, 



CHAS. LYELL, 



In the year 1869, the British Association for the Advancement 

 of Science met at Exeter, and Harkness, who had been a constant 

 attendant at these annual meetings for many years past, was elected 

 President of the Geological section, and chose for the subject of 

 his Presidential Address that of the relation of the Devonian rocks, 

 properly so-called, to the strata next to them in age. In this 

 address he may be said to have summarised the results of all his 

 observations upon the great group of strata whose absence in 

 Cumberland and Westmorland has given rise to the well-known 



