BEISTOL BUILDING STONES. 



97 



sjonitic gi'anifce does not yield til] tlie load readies 6'74 

 tons. 



In granite districts, wlioro tliis rock is locally used for 

 ecclesiastical purposes, the work is heavy, the material 

 being too stubborn to admit of grace or lightness of finish. 



Ornamental pillars of polished Scotch and Cornish granite 

 are used in the Promenade and other parts of Bristol. They 

 are also conspicuous in the interior of the Church of St. 

 Jamos-in-the-Barton, and in that of Norton Malreward, 

 Somersetshire. The introduction of polished granite pillars 

 in a building containing Norman work is a somewhat 

 torturing piece of " barbaric splendour." 



I am not aware that any trap rock is used in construction 

 in our own neighbourhood. Indeed the use of such rock is 

 exceptional. A brown trap has however I believe been used 

 with considerable effect in the roof of Exeter Cathedral. 



Passing from the granites to the sandstones, there are 

 three local rocks of this class used in the neighbourhood 

 of Bristol, — Millstone-grit (k)cally " firo-stono "), Pennant, 

 and Old Eod Sandstone. 



Millstone-grit, or fire-stone, is a-n exceedingly hard, tongh 

 rock, composed of gi'ains of sand cemented by a silicious 

 or folspathic cement. The specific gravity is 2-62. A cubic 

 foot of the rook weighs about 161 lbs. Subjected to crushing 

 stress in the testing machine in the Univei'sity College, 

 Bristol, a cubic inch of a close-grained variety of this rock 

 from Long Ashton quarry began to split at lO'l? tons, and 

 broke down at 13 tons. A two-inch cube of a somewluxt 

 less compact rock from the same quarry began to split at 

 11-17 tons, and broke down at 19'39 tons. The former 

 gives the highest resistance of our local stones. (See Ap- 

 pendix.) The more absorbent varieties of this stone a-s 

 used in construction seldom take up more than one pint 



