Address to the Lincolnshive Naturalists’ Union. 27% 
Now rain may seem but a weak agent for forming hills, and 
scooping out valleys, but, with the help of frost and the corroding 
forces of the atmosphere, without doubt it effects the task. 
Both hill and valley have one common origin, they are the 
remains of surfaces, once planed and levelled by the sea (I am 
not here speaking of volcanic force), which, when raised above 
the waves, were carved and cut into shape by the rain; the 
| harder parts, the most capable of resisting erosion, forming the 
; 
| hills; and the softer portions; the most easily denuded, forming 
. the valleys. 
Rising as vapour, mist, and cloud, and falling again on the 
earth, rain is the source of all our lakes, springs, and tivers ; and, 
through rivers, the source of continents also, by the deposition of 
sediment on the floors of oceans and seas, and by the silting up of 
shallow bays and estuaries. 
Its work never ceases, and, aided by frost, and the chemical 
components of the air, it penetrates and dissolves the hardest 
rocks, and nothing is free from its action. Rivers can cut only 
narrow channels, and it is left to rain to widen them into valleys. 
No drop of rain runs an inch on the surface without setting some 
soil in motion toward a lower level. 
‘The amount of erosion depends, of course, greatly on the suil 
on which the rain falls: On clays, like those of the Lias, it works 
far greater havoc than on sandy or gravelly soils; though, with- 
out due thought, the reverse might appear to be the case. Mr. W. 
Whitaker, of the Geological survey, in discussing the age of man 
at the recent British Association Meeting, well observed this, 
when he said, ‘“‘ When rain falls on gravel and sand, which are 
open and porous, they say ‘Oh! come in, there’s plenty of room,’ 
and in it goes, and comes out againas a clear spring of water at 
“the base ; whereas, when it falls on clays and stiff soils, they say, 
‘We don’t want you and we won't have you,’ and the rain, in 
_ response, washes hundreds of tons away from the surface ;”’ show- 
_ ing that resistance is not always the best policy. 
