22 



KIMERIDGE CLAY 



valve, h, on the inner end of this flue is closed, the heated air enters by the open 

 . valve, Jc, in the annular chamber or passage, I. The warm air then traverses the 

 chamber, e, passes through the only open valve, m, of the series into the flue, n, of 

 the series, the end of which in the smoke chamber is closed by the valve, o, and 

 thence to the drying-chamber, 4, and chamber, 3, and finally escaping at d by the 

 flue and open plug or valve, h, into the smoke chamber, c, and chimney, /; the whole 

 of the valves, h, o, k, and m, are kept closed, except those which are in connection 

 with the flues for the time being ; and, so soon as the goods in the drying-chambers 3 

 and 4 are sufficiently dry for burning, the doors, b, are removed, and replaced at b', 

 exposing the bricks in the chamber 3 to the direct action of the heat from the kiln- 

 fires, whilst the chamber 5, just filled with green bricks, forms, with the chamber 4, 

 a drying-chamber. A fresh set of valves or dampers is now opened, and the opera- 

 tions of burning and drying proceed in a continuous manner. 



Kilns for special purposes demand especial contrivances ; but, usually, they are in 

 principle like one or other of those which have been described. For Malt-Kiln, see 

 MALT. 



KIMEKI23CE CXiAV or SHAXiE. The sands which underlie the Portland 

 stone of Dorsetshire and the south-west of England are based upon a considerable 

 thickness of dark brownish- or bluish-grey clay, to which the term Kimeridge Clay 

 has been given by geologists from the circumstance of its being largely developed and 

 well displayed in the neighbourhood of the village of that name. 



Throughout the Isle of Purbeck, but especially in the part of it in question, the clay 

 assumes a very shaly and bituminous character, sometimes passing into more massive 

 beds of brownish shaly coal, possessing a conchoidal fracture. 



The Romans, and also the Celts who inhabited the country previously to its inva- 

 sion by the former nation, appear to have manufactured the harder portions of the 

 shale into cups and other articles, but chiefly into beads, armlets, and bracelets, 

 specimens of which last have been found in the neighbouring barrows, in some cases 

 still encircling the wrists of skeletons. 



Circular discs of shale, about the size of a penny piece, have also been dug up in 

 great numbers in this part of the Isle of Purbeck : as many as 600 were, upon one 

 occasion, found closely packed together. 



Authorities have been much divided in opinion as to the origin and use of these 

 circular pieces of shale. By some they are supposed to have passed current as money 

 or tokens, whence the name of Kimeridge coal-money, by which they are commonly 

 known, has been applied to them ; but the most probable supposition is, that they 

 were the portions of the material fixed to the lathe, and left adhering to it after the 

 armlets or other ornaments of a similar description had been turned from their outer 

 circumferences, and that at some subsequent period these refuse pieces of the turner 

 were worn as amulets or charms by the superstitious. 



The shale around Kimeridge abounds in animal and vegetable matter, the former 

 consisting of the shells of oysters, ammonites, &c., together with the bones and teeth 

 of large saurians and fish ; while the latter is in so finely divided a state as not to 

 be distinguishable to the eye. Much carbonate of lime and pyrites are also present, 

 especially in those portions in which animal remains are most abundant. 



The variation in the external character of the shale is accompanied by a corre- 

 sponding variation in the relative proportions of mineral and organic matter contained 

 in it ; those portions which are the mose fissile and slaty containing a large proportion 

 of mineral matter combined with a relatively small proportion of organic matter ; 

 while, on the other hand, in the harder and more massive portions which break with 

 a conchoidal fracture, the organic matter is greatly in excess of the mineral matter, as 

 is shown by the following analyses : 



When heated the shale gives off copious fumes of a. disagreeable odour resembling 

 that of petroleum ; and when ignited it burns of itself with a dull smoky flame, 

 leaving, when freely exposed to the atmosphere, a reddish ash, which generally re- 

 tains the form of the original fragment. 



