11 



daily amount of rain reached only I'Ol inch, the aggregate for 

 the month was 8-32 inches. The rainfall at Longthorns last year 

 exceeded that of the two preceding years by nearly six inches. 



Taking the whole of Dorsetshire as 988 square miles, we 

 shall have a mean daily fall of rain of 950 million gallons. 



Scientific attention has been of late largely devoted to an 

 exhaustive study of the geological structure of England with 

 reference to the water-bearing formations, which are at com- 

 paratively moderate depths, and to the possibility of making 

 them accessible for man's use. It is remarkable how the 

 physical structure in this respect influenced the early residents of 

 a district in their choice of settlements, and determined the sites 

 of many of our towns and villages. The removal of the rain- 

 water from the earth's surface (omitting evaporation), is variously 

 provided for by nature, either by drainage into streams and rivers, 

 which cut through the impermeable clays, or by absorption into 

 the strata, as in the chalk and limestone districts, whereby the 

 water is conveyed through fissures. The springs at the foot of 

 pur Chalk downs, which rest upon the Gault or Oolitic clays, 

 intervened by a thin stratum of Greensand, are much stronger 

 and more profuse than those which issue in the valleys which do 

 not reach below the Chalk level, and which in many cases become 

 dry during the summer, as at Houghton, Milton Abbas, &c. Here 

 the streams rise from springs thrown off in the low valleys where 

 the Chalk soil is less absorbent. 



The Chalk beneath the surface soil is usually fissured, allow- 

 ing the rain to pass through freely for a few feet, but is arrested 

 when it reaches the compact, undisturbed mass, and only obtains 

 access to the lower levels by cracks and fissures ; after long-con- 

 tinued rains the Chalk becomes fully saturated and even to 

 overflow. That communications with the outer air occur at great 

 depths may be inferred from a case which came under my notice 

 last year when I was sinking a well at Clenston, the miner 

 reached a region of disturbed chalk several feet in thickness, at 

 dip of 45 in a north-westerly direction, and about 110 feet 

 from the surface, where he encountered a blast of atmospheric 

 air so strong that his candle was blown out, and he was obliged 

 to complete his work in the dark ; he otherwise felt no inconve- 

 nience, nor was his respiration affected. 



It is obvious from what has been said that while water lies 

 at the higher and lower levels of the Chalk districts, the inter- 

 mediate mass is usually dry, the springs, therefore, issuing from 

 the valleys which rest only upon the Chalk must have an inter- 

 mittent and uncertain supply of water. 



I have ventured to dwell upon this subject, because the capa- 

 bilities of the Chalk as a source of deep water supply for large 

 towns has been maintained by many, and has been the subject of 



