208 EEY. J. p. BLAKE ON THE 



In the general section of Swindon (see PI. YIII. fig. 5) we may 

 therefore include all the deposits from a to /, as : — 



No. 1. This is shown to be exceeding local in range, and different 

 in character from any other Portland rock ; but its origin cannot be 

 satisfactorily discussed until after the description of the succeeding 

 beds. 



]!^o. 2, hitherto called the "basal sands," have much of that 

 character; but even when most sandy they are still calcareous, and 

 in parts consist of comminuted shells. There are many irregular, 

 hardened, calcareous blocks, and some lines crowded by Trigonia 

 gibbosa of many varieties and other shells, especially about 9 ft. from 

 the base. A good deal of it is false-bedded ; and the blocks often 

 lie parallel to the false dip, and not to the true. It is of uneven 

 thickness, owing to erosion at the top ; the maximum measurement 

 is 27 ft. It would be impossible for any one who, like Dr. Pitton, 

 had examined the Portland series in other districts to mistake the 

 nature of these rocks. They are the obvious equivalents of the 

 Tisbury stone and the lower portion of the flinty series at Portland. 

 Here they have a minimum of consolidating silica, at Portland a 

 maximum. They are accordingly so described by him ; and in this 

 he is followed by Godwin- Austen and Damon. But, for some reason 

 (nowhere stated), the Geological Survey has called these beds Portland 

 Sands, and coloured them so on the map ; and hence they have been 

 in late years so considered. This has led to further errors and to 

 an unfortunate overlooking of the true Portland Sand in this district. 

 The principal fossils of these calcareous sands (besides the usual 

 Trigonia, Perna, &c.) are Ostrea solitaria, Lima rustica, Mytilus 

 unguiculatus, Cyprina pulchella, Corbula dammar iensis, and Pleuro- 

 mya tellina ; but they are not common. 



No. 3. The beds which follow these in the quarry, and which 

 appear to have been seen only by Mr. Godwin- Austen, are of consi- 

 derable interest. They are very fossiliferous, and present a greater 

 development than the corresponding beds at Tisbury and Portland. 

 They are only seen in the deepest parts of the great quarry — at the 

 present time towards the south-west end. Here are 7 ft. of rubbly 

 limestone-rock full of Trigonia gibbosa, the middle part entirely 

 made of them. This is used for roads only ; but the lowest part 

 is said to be burnt for lime. At its base is a great accumulation of 

 Lydian stones, or grains of glauconite. These subdivisions do not 

 seem very constant in character, nor the shells always the same ; for 

 the section given by Mr. Godwin- Austen of the opposite (N.E.) 

 corner is somewhat different in detail. Portunately, however, these 

 beds have a wider range and some economic value, and hence are 

 quarried at several places in the neighbourhood. The nearest to 

 Swindon is that, long known, on the north of the road to Coate. 

 Here are two sections succeeding one another on the dip, which is 

 to the south. In the first, nearest the road, only the ordinary sandy 

 beds, with their great indurated blocks (as in the great quarry), are 

 to be seen ; but in the second, succeeding these in perfectly clear 

 sequence, are the following : — 



