Xu PREFATORY REMARKS 



on a more remarkable scale than usual, had just taken place in 

 the history of Geology. The evidence of almost all the first 

 English authorities in regard to certain fish-spines and de- 

 fences said to be found in the regions of Lower Siluria had 

 broken down. They had mistaken portions of Crustacea for 

 portions of fish. * Accordingly, nearly a whole chapter of the 

 " Foot-prints," founded upon these supposed discoveries, had 

 to be erased, and some portion of the work re-written. " I 

 must omit that chapter," said the author, " and strengthen 

 the general argument." But pressure of other work, an 

 increasingly irritable brain, and severe attacks of inflamma- 

 tion of the lungs, to which he was subject in his latter years, 

 prevented these intentions from being fulfilled. I think, 

 too, that he was partly influenced by a desire to wait, in 

 order to see what direction the progress of real discovery 

 was likely to take. Was the Upper Ludlow bone-bed, at 

 the top of the Silurians, to be the final resting-place where 

 ichthyic life had its first beginnings? or was discovery of a 

 more solid kind again to take its course downwards ? Might 

 not this chapter be soon supplanted by another, when geolo- 

 gists, guarded against erroneous conclusions by former mis- 

 takes, would be able to prove the earlier introduction of 

 fish by evidence quite unimpeachable ? Alas ! were his hand 

 now engaged on the task before me, a very noble chapter 

 would doubtless have been written, in lieu of that which he 

 intended to efface. It is true that re-discovery does not 

 progress very rapidly, but it moves surely in the direction 

 he anticipated. Many hundred feet below the Upper Lud- 



• See Mr Salter's Note, p. 815. 



