gg THE GEOLOGIST. 



and houses, with their designs and purposes; but, if we stand on a 

 pinnacle of the still higher spire of a cathedral, we cannot comprehend 

 the details of the great city below us without a plan of its structure and 

 the accompanying references to its principal edifices. Still more 

 difficult is it to stand on the mountain -peak, and, even with a carefully- 

 constructed map, to gaze over the apparently interminable ranges of 

 hills upon hills, as they rise fainter and fainter in the grey distance, 

 and to carry off in the mind a just comprehension of the scenery, or of 

 the ever- varying characters of the country. How much harder, then, 

 when our view is world-wide — and should, to be perfect, be world-deep 

 also— for the mind properly to grasp the whole expanse. The outlines of 

 the great territories of the past have been only partially mapped ; the 

 references to the principal points may be correctly marked ; but where 

 everything is toned down by regularity of succession, and by the 

 obscurity of time, it is only the most prominent features or the great 

 catastrophes and remarkable events that enable the perceptive faculties 

 to conceive that frame- work into which they afterwards, by study and 

 perseverance, fit the more ordinary phenomena, and fill up the spaces 

 as a child fits in the intermediate slices of its puzzle. 



Of what are the ancient rocks composed ? — Of the beaches, sand?, 

 and ooze of the ancient seas and oceans, of the sediments of the rivers 

 and lakes, of the vegetable and organic remains of successive and 

 departed creations. Just as, on our coasts, we find the beaches, sands, 

 and silts derived from the waste of the land, and the rivers bringing 

 down to their lakes and estuaries the disintegrated particles of the 

 soil and the produce of the earth. 



We see in the stratification of the rocks the evidence of such de- 

 positions ; and we see in their materials the sources whence they were 

 derived. 



We see in the drift-bedding of the ancient sands the effects of 

 currents piling up the shifting banks in the primeval channels ; we can 

 measure the angles of the party-coloured layers of sand, as they incline 

 to various points around ; and thus we can map the ancient shoals, and 

 by the gentleness or the steepness of their slopes and by their other 

 features, we can perceive whence the current came, how it rolled the 

 particles along, and levelled off the tops of the banks. 



Wo examine the boulders and pebbles of the ancient conglomerates, 

 and wo match them with well-known mountain-rocks from far and 



