33^ JURASSIC. 



Economic products, etc. 



The so-called Kimeridge Coal has for a long period been worked on the coast by 

 Little Kimeridge and north of Hen Cliff. The shales here are more or less 

 bituminous, but the best or Black Bed is dug out of the cliffs 12 to 14 feet from the 

 top. The bituminous matter is probably of animal origin. It has for many years 

 been used by cottagers in the neighbourhood as fuel, and is still so employed, but it 

 emits an unpleasant smell while burning. About the year 1768 it was regularly 

 worked and sold at ds. a ton. At times it has been employed in making naphtha, 

 candles, and even gas.' A company is now engaged in digging or mining it, with 

 works near Wareham, where not only mineral oils, but tar, animal charcoal, and 

 carbolic disinfectants are prepared. Bituminous shale has been dug for fuel at 

 Portland, south of Chesilton : this shale may be distinguished from non- 

 bituminous or feebly bituminous shale, by the peculiarity that a thin paring curls 

 up in front of the knife, and shows a brown lustrous streak.- 



INIessrs. Buckland and De la Beche state that near Portland Ferry a portion of 

 the Kimeridge Clay at one time "presented the appearance of slate burnt to the 

 condition of red tiles, " evidently due to the "pseudo-volcanic phenomena" that 

 were in 1829 exhibiting themselves in the same stratum at Holworth Cliff, Ringstead 

 Bay. Here combustion began in September, 1826, and during a period of many 

 months, considerable volumes of flame were emitted, probably originating in the 

 heat produced by the decomposition of the iron-pyrites with which this shale 

 occasionally abounds. The extent of the surface of clay which was burnt did not 

 exceed 50 feet square. Within this space many small fumaroles exhaled bituminous 

 and sulphureous vapours, and some of them were lined with a thin sublimation of 

 sulphur.'^ 



Alum is said to have been formerly made from the shales in the parish of 

 Kimeridge. 



Many fruitless trials for coal have been made in this formation, in Oxfordshire, 

 Berkshire, and Dorsetshire. 



Bricks and tiles are made in many places. The cement-stones of Kimeridge 

 have been manufactured into cement, and perhaps from their being used in the 

 neighbourhood (Weymouth) they may have given rise to the name Portland cement. 

 Such cement is now made from the Kimeridge cement-stones at Sandford, near 

 Wareham. 



Near Smedmore, in the parish of Great Kimeridge, there is found what the country 

 people call ' Coal-nioiuy,'' generally in the soil on the top of the clitfs, two or 

 three feet below the surface. This ' money ' consists of circular pieces of shale, 

 from two inches to three and a half in diameter, and a quarter of an inch thick, on 

 one side flat and plain, on the other convex with mouldings ; on the flat side are 

 two or three small round holes, and sometimes one square hole. It is considered 

 probable that the Kimeridge coal-money may be simply the refuse from which rings 

 or armlets have been turned in a lathe, or they may be the bases of vases or bowls.* 



The Kimeridge Clay forms broad vales which are naturally unproductive, the 

 soil being cold and stiff. Most of the land is in meadow or pasture. Oaks grow 

 well upon it; hence the name ' Oak Tree Clay,' applied by William Smith. 

 There are no springs, excepting those which break out along lines of fault. 



1 Damon, Geology of W^eymouth, 1SS4, p. 58; J. C. Mansel-Pleydell, Geol. 

 Dorset, G. Mag. 1873, p. 407. 



- A. Geikie, Text-Book of Geology, edit. 2, p. 173. 



3 T. G. S. (2), iv. 22. 



* J. Evans, Ancient Stone Implements, p. 41S ; Conybeare and Phillips, Geol. 

 England and Wales, p. 1 7 7. 



