APPENDIX 179 



chalk, or the rock immediately underlying the one or 

 overlying the other. Those that rise in the lower cretace- 

 ous or wealden deposits, break through the line of chalk 

 hills and cross a considerable distance of chalk. Those, 

 on the contrary, that rise on the ocean deposits, hardly 

 leave them till they reach the sea. Advancing westwards 

 where the oolites and lias are crossed, and the new red 

 sandstone entered, we find a few streams of no great 

 importance running over those rocks, especially in the 

 eastern part of Devonshire. After this we enter the 

 region of igneous and metamorphic rocks, and the drain- 

 age, whether to south or north, runs almost entirely over 

 material little permeable, and not likely to retain, even 

 for a short time, any considerable part of the fall. The 

 flow of the streams here is large compared with the rain- 

 fall, but on the whole inconsiderable for want of breadth 

 in country crossed. The country rises to a considerable 

 elevation in Cornwall and Devonshire, and the sources 

 of the rivers, whether from springs or surface drainage, 

 are often very abundantly supplied. The rainfall being 

 frequent they rarely fail, and are not often lowered for a 

 long period of time. 



" 5. Rainfall. — The rainfall over the western part of the 

 district is heavy, and the number of rainy days very con- 

 siderable ; but advancing eastward the quantity of rain 

 sensibly diminishes, and the distribution is also greatly 

 modified. In some parts of Cornwall the fall amounts to 

 47 inches ; but even in that county exposed to warm moist 

 w^inds blowing from the Atlantic, there are spots where 

 it is said not to exceed 22 inches. The average of the 

 district is taken at 36 inches. In Devonshire, or Dart- 

 moor, the fall exceeds 52 inches; but at Sidmouth is 

 said not to exceed i6|-. The fall is very great on the 

 high ground in the middle of the country ; but in the 

 sheltered ncoks on the coast looking towards the east is 

 everywhere comparatively small. In Somersetshire the 

 fall is only 19 inches at Taunton, but increases towards 

 the west and north. In Dorsetshire it ranges from 18 J 

 at Abbotsbury to 29 at Blanford. In Hampshire it appears 

 to be considerable, and towards western Sussex is found 

 to amount to 34, while in parts of eastern Sussex it 

 appears to be 2>^. At Hastings, though still consider- 



