226 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Apr. 7, 



Capt. Moody, about 1 920 acres of surface. It at first flows through 

 a narrow and uncultivated ravine, which, three miles above the small 

 town of Holmfirth, opens out into a narrow valley. This valley has 

 always been subject to occasional floods, arising, however, from 

 natural causes : one of the most disastrous occurred in 1777. The 

 bottom of the valley shows beneath the turf an accumulation, several 

 feet thick, of local gravel and rolled fragments of rocks. In some 

 places debris of this description overlies 2 to 3 feet of imperfect peaty 

 matter, which again appears to repose on similar detrital accumula- 

 tions. This drift, however, is much water-worn, and does not seem 

 to contain any masses of rock at all approaching to the dimensions of 

 those transported by the late flood. 



The following outline map shows the course of the stream and the 

 situation of the principal places referred to. 



Fig. I . — Course of the River Holme and Bigley Stream. 



Fig. 2.— (See p. 229.) 



Between 1840 and 1844, an embankment 9Q feet high (but which 

 afterwards subsided to 87 feet), about 480 feet wide at base, 16 feet 

 at top, and 340 feet in length, was thrown across the valley of the 

 Digley, three miles above Holmfirth. By this means an artificial lake, 

 known as the Bilberry Reservoir, about a quarter of a mile long, 

 300 to 400 feet broad, with a surface of rather more than 1 1 acres, 

 and in the centre from 70 to 80 feet deep, was formed. It was cal- 

 culated that, when full, this reservoir held 86,248,000 gallons of 

 water. The dam was constructed of a wall of clay-puddle, 8 feet wide 

 at top, and 16 feet at bottom, with a mass of the debris of the valley, 

 consisting of earth and stones, on either side. The inner slope was 

 paved with squared stone, and had a base 3 to 1 ; the outer slope, a 

 base of 2 to 1 . 



On the night of the 4th of February last, the giving way of this 

 embankment caused the sad catastrophe, of which the papers have so 



