GUERNSEY CLAYS. 215 



" Plastic Clay " is technically applied to clay of a grey colour, 

 which burns white in the kiln, and is used as a fire-clay ; ours 

 therefore cannot be properly called plastic clay. The clayey 

 loam seems to vary from the plastic variety mainly from the 

 large proportion of sand it contains, and even our purest clays 

 when washed are found to contain a good proportion of sand 

 with angular surfaces. 



The deposit at the Vrangue is the one which requires 

 most special investigation, for here only are found three 

 superficial deposits overlying each other: — 1st, A layer of 

 clayey loam. 2nd, Good clay, so strong as to have to be 

 mixed with other material before being used for brick-making. 

 3rd, A stratum of sand. The pit has been sunk to a depth of 

 about 20 feet ; the thicknesses vary, but may be put down as 

 (in the centre of the pit) 4 feet of loam, 3 feet good clay, 2 feet 

 sand; the rest disintegrating rock worked for gravel, and 

 traversed by numerous veins, some changing into Kaolin. 



The sand diminishes towards the south end or higher 

 part of the pit, just disappearing where the works terminate. 

 In one spot it is intersected by a narrow vein of bluish clay, 

 and resting on this I found in the sand the stones exhibited ; 

 elsewhere the sand is uniform. I searched well, but could 

 find no signs of shells, and the sand gives no reaction with 

 acids, which it would do if particles of shell were present. 

 The manager of the brickfield showed me two large flint 

 pebbles which he said had been dug out at the base of the 

 sand. We found some at the base of the clay. 



We have no means at present of determining how far 

 this sand extends. At Millbrook clay-pit, about 300 yards 

 west, neither sand or good clay is to be seen, clayey loam 

 only. On the other side of the adjoining road, i.e., eastward, 

 the face of the old pit is masked by a wall and cannot be 

 examined. All we know is that the sand extends from south 

 to north about 50 feet, and from east to west about 10 feet. 

 From the south-east corner of the pit it thins out and dis- 

 appears about 10 feet to the west. The hill slopes downward 

 to the north, and about 200 yards in that direction a new 

 sinking has been made, where good clay, more plastic than 

 any in the old pit, has been found, but it is thickly and irre- 

 gularly intermixed with large angular fragments of local rock, 

 the whole having a totally different appearance from that in 

 the upper pit ; it looks as though it had been washed down 

 with the angular stones from the upper part of the hill. 



In most of the pits the change from loam to plastic clay, 

 or from loam or clay to gravel or the decomposing rock 



