GEOLOGY. 57 



labourer told me that he had found in it a large worn 

 tropical Volute shell, such as may be seen on the 

 chimney-pieces of cottages ; and as he would not sell 

 the shell, I was convinced that he had really found it 

 in the pit. I told Sedgwick of the fact, and he at 

 once said (no doubt truly) that it must have been 

 thrown away by some one into the pit ; but then 

 added, if really embedded there it would be the 

 greatest misfortune to geology, as it would overthrow 

 all that we know about the superficial deposits of 

 the Midland Counties. These gravel-beds belong in 

 fact to the glacial period, and in after years I found in 

 them broken arctic shells. But I was then utterly 

 astonished at Sedgwick not being delighted at so 

 wonderful a fact as a tropical shell being found near 

 the surface in the middle of England. Nothing 

 before had ever made me thoroughly realise, though 

 I had read various scientific books, that science con- 

 sists in grouping facts so that general laws or conclu- 

 sions may be drawn from them. 



Next morning we started for Llangollen, Conway, 

 Bangor, and Capel Curig. This tour was of decided 

 use in teaching me a little how to make out the 

 geology of a country. Sedgwick often sent me on 

 a line parallel to his, telling me to bring back speci- 

 mens of the rocks and to mark the stratification on a 

 map. I have little doubt that he did this for my 

 good, as I was too ignorant to have aided him. On 

 this tour I had a striking instance how easy it is to 

 overlook phenomena, however conspicuous, before 

 they have been observed by any one. We spent 



