i8so RUNNING SECTIONS 163 



bothered, but glad too, as I never saw the Malvern 

 section. 



' Our work here fearfully differs from Sir Henry's, 

 and the worst of it is that he has, I think, published 

 his opinion in his Anniversary address. It is about 

 certain black slates which he puts under the Cam- 

 brian : they being, in fact, the Lingula (Silurian) beds 

 brought against it again by a fault. It will be not a 

 very agreeable job convincing him of this.' 



The visit to Malvern and a hurried journey to 

 London took up only some ten days, and by the 22nd 

 June he was back once more at Llanberis to begin 

 the arduous task of running sections. This operation 

 was conducted with a theodolite and chain, the sur- 

 veyor having the assistance of two men. The line of 

 section having been determined in such wise as to 

 cross the most instructive or important geological 

 structures, and generally the loftiest summits, was 

 drawn upon the map, and the surveyor then proceeded 

 to measure on the ground the horizontal distances, and 

 fix the relative heights of the various points along the 

 selected line. These measurements were entered in a 

 field-book, from which the section was afterwards 

 plotted on a scale, vertical and horizontal, of six inches 

 to a mile. When the outline of the ground had in 

 this manner been correctly drawn, the geological 

 structure was inserted from the maps and note-books, 

 and, where needful, a final visit was made to the ground, 

 and minor details were adjusted on the section. 

 These operations, it may easily be believed, required 

 both care and skill. They provided a further means 

 of checking the accuracy of the maps, and when 

 successfully completed, they furnished the surveyor 

 with a valuable additional store of materials for the 



