262 Messrs. Bucrland's and Conyeeare's Observations on the 



These coal-seams are kept longer in the field than they would otherwise 

 have been, by a series of faults, the principal of which ranging from north to 

 south through Clan Down, throws up the coal-measures on the eastern side of 

 the fault 100 fathoms. Another ranging through theWelton works about a mile 

 to the west of the former, throws up the measures on the same side of the 

 fault 70 fathoms. There is another running east and west to the south of 

 Timsbury and High Littleton, which raises the strata to the north 70 fathoms. 

 This fault, like that of Bitton, affects the red marl and the incumbent lias. 

 There are numerous faults of more limited extent. One of these, which tra- 

 verses Paulton-hill from east to west, and raises the strata to the north 20 fa- 

 thoms, affects also the overlying formations, so that the oolite on the south 

 abuts against the lias on the north to the depth of 20 fathoms. Another fault, 

 which affects both the coal-measures and the overlying strata, passes immedi- 

 ately to the north of Houndstreet. The ground here falls in three successive 

 terraces from the hill above Houndstreet on the south to the vale of the river 

 Chew on the north. The highest terrace is crowned with lias, the red marl 

 appearing on its slope ; the coal-measures crop out so as to form the middle 

 terrace, on the brow of which Houndstreet is situated : on the third and lowest 

 terrace the lias re-appears, extending eastwards from the north east wall of 

 Houndstreet park across the lane to Wick farm. The subsided mass of lias 

 is for the most part horizontal, but in one place its strata are bent into a sharp 



arch, in the manner represented. .x^^;v____^ On the escarpment to- 

 wards the river the coal-measures ^'^"^^ again appear. Here then 



is a fault by which the lias and the coal-measures which support it are thrown 

 down on the north to a depth exceeding the whole thickness of the red marl. 

 These faults are fissures penetrating the strata in every direction, and with 

 every degree of inclination to the horizon and to the planes of the strata which 

 they traverse ; a nearly vertical position however is by far the most common. 

 Both the level and inclination of the strata on either side of the fault are 

 usually altered ; occasionally however they remain the same, the strata being 

 simply fractured. The fissures are usually from a few inches to 3 feet broad, 

 but are often of much greater dimensions. They are generally filled by a 

 compact seam of clay, forming a natural dam or wall, impervious to water, and 

 called the clog, which the miner studiously avoids to penetrate. It often hap- 

 pens that the edges of the strata to a certain distance from the fault, sometimes 

 exceeding 100 feet, are so much shattered and broken, that it is impossible to 

 work them. This shattered interval is called the dead ground of the fault. It 



