Sketch of the Geology of the Neighbourhood of Shaftesbury. 175 



different systems are represented by different colours, the variety is 

 still more striking. In the map before you, copied from portions of 

 Sheets 15 and IS, embracing a rectangular area o£ twenty-four 

 miles east and west, by twenty-two miles north and south, no .less 

 than ten different colours are used, and these show that within this 

 area ten different rock formations reach the surface, or are only 

 thinly overlaid by the skin, so to say, of surface-soil, due to the 

 decomposition of mineral, vegetable, and animal matter, aided by 

 the plough and the earth-worm. 



I must now take you back for I know not how many thousands 

 of years, to the time when those rocks of which I have spoken were 

 being slowly deposited, as sediment, upon the floors of seas, shallow 

 or deep, or in the deltas of large rivers. It is difficult to know 

 where to begin the description, but I think it will be best to imagine 

 that the red rocks of the trias have been already deposited in vast 

 inland lakes, for in the Triassic Age, you must remember, that 

 what is now England formed part of a continent of which modern 

 Europe was also a part. A gradual subsidence of the land then 

 began, and a series of islands were formed. The old rocks of Wales, 

 Devon, and Cornwall, which now, although they have endured for 

 countless ages the inevitable waste which rocks exposed to the air 

 always suffer, still may be classed as mountains, then rose over the 

 Jurassic sea, and round their shores the lias, and then the oolite 

 beds, were deposited in salt water. The lias clays are well seen at 

 Lyme, and are noted for the fossil remains of ammonites, belemnites, 

 and nautili, and of those immense lizard-like reptiles whose 

 skeletons — sometimes over 20ft. in length — have been found well 

 preserved in the blue clay. The lias district in many places is 

 somewhat flat, or only gently undulating, and forms good pasture 

 land. Next we come to the lower oolites, which, commencing 

 between the Chesil Bank and Bridport, stretch by way of Beaminster 

 and Sherborne to Bath and onward. They consist chiefly of yellow 

 limestone, often composed of rounded grains, like the roe of a fish, 

 cemented by calcareous matter. From this peculiar appearance the 

 name of oolite, or egg-stone, is derived. I must not describe these 

 rocks in any detail, but must come nearer home and call your 



