DISCOVERY 



215 





Fig. I.— the new pit, showing method of removing top gravel i.'VERI.VlNG 60 FEET OF OXFORD CLAY. 



shells, stones, which are all objectionable in varying 

 degrees according to their quantities. 



(2) Must not be too plastic or " foul " ; such a clay 

 would shrink or crack on burning. The appearance 

 of lime would indicate such a clay. 



(3) Must not be too " lean," i.e. it must be plastic 

 enough to hold together during the process of drying ; 

 the appearance of grains of sand would indicate 

 such a claj'. 



The Oxford clay, called " Knotts " in the district 

 under consideration, approximates very nearly to the 

 above ideal conditions. The clay is dug in large open 

 pits some 60 to 80 feet in depth, upon which there lies 

 superimposed a stratum of some 5 to 12 feet of gravel 

 or of clay containing numerous glacial stones and 

 boulders. Fig. i shows a common method of removing 

 the top deposit, which is loaded into tip-wagons and 

 deposited into a neighbouring pit from which all 

 the clay has already been dug. The clay itself is won 

 by means of steps (Fig. 2) on which the men work with 

 crowbar, pick and shovel ; and the clay is sufficiently 

 hard to stand, winter or summer, without subsiding 

 or falling ; and although some of the quarries are 

 upwards of 80 feet deep, the men work on the ledges 

 with perfect safety. Fig. 2 also shows the steep in- 

 clined cutting made in the maiden clay to act as a 

 shoot for the material, with the tip-wagon at the 

 bottom ready to receive the spoil. The floor of thr 

 quarry is at (or near) the stratum of Kelaways Rock, 

 which forms a comparatively hard and dry workini; 

 floor. It is not, however, everywhere in the district 

 that such good conditions prevail ; locally the top 

 gravel -deposit or " callow " varies remarkably, and the 

 local geology has to be known in detail in order to 

 determine the best sites for sinking new pits ; in one 

 quarry it was found that a glacier or a river had scooped 

 out more than half the Oxford clay and redeposited 

 in its stead a silt, containing stones, gravel, etc., which 

 material was quite unsuitable for brick-making. Hence 

 the quarry had to be abandoned at considerable loss. 



From the pits of this district have come some of 

 the famous fossilised saurians, collected by Major 

 Leeds, which are now housed at the British Museum, 



Fig. 2.— showing METHOD OF WINNING THF; CLAV Willi bll.PS 



AND SHOOT IN- FOREGROUND. 



The tranuvay incline and works in background. 



South Kensington. Two or three galleries are devoted 

 to the collection which is known as the " Leeds Collec- 

 tion." 



It is unfortunate for the geologist and fossil-collector 

 that the method of quarrying, shown in Figs, i and 2, 

 except in the deepest of pits, is fast disappearing 



