142 Correspondence — J. Smith. 



RAILWAY SECTIONS IN ATESHIRE AND LANARKSHIRE. 



SiK, — At present there are some railway sections through Drift ia 

 the line being constructed from Darvel, in Ayrshire, to Strathavon, 

 in Lanarkshire, which, I think, show features demonstrative of 

 a depression of the land, and the marine origin of at least part of 

 the Drift beds. Lately, with two friends (it was my fourth visit 

 to the locality), I examined minutely one of these sections, 500 

 to 600 feet above sea-level (estimated from a bench-mark). This 

 cutting is to be a deep one, and is being taken in two ' lifts ' ; about 

 200 yards of the upper lift can at present be examined, but it is 

 much longer, part of the slope being already pick-dressed. The 

 section is almost horizontal for the above-mentioned distance, and 

 very regular — not at all twisted or disturbed, as is the case with 

 many parts of the Drift. It is about two miles east of Darvel. The 

 following beds are exposed : — 



1. Sand and gravel, stratified ... ... ... ... 15 feet. 



2. Ston}' Boulder-clay -with large blocks 6 ,, 



3. Laminated clay with few stones and large blocks ... 5 ,, 



4. Stony clay 3 ,, 



5. Sharp sand, not cut through. 



In bed 1, I observed a long boulder of Matstone Hill granite, 

 quite in a vertical position. In beds 2, 3, and 4, long boulders were 

 obtained during the progress of the cutting, in a similar position. In 

 the laminated bed 3, a large striated boulder of white sandstone is at 

 present to be seen, measuring four feet in diameter. It has clearly 

 fallen into the clay when the latter was in a soft state, as the laminae 

 at the bottom corners of the block are bent down under it, showing 

 that the block in falling has made a small indent in the laminated 

 •clay. They (the lamina3) also curved over the top of the block. 



Another interesting feature was the depressions or ruts in the 

 stony clay bed 2, these being invariably filled more or less with 

 laminated clay. A number of shell-fragments loitli the epidermis 

 were picked out by us from the stony clay, and from the laminated 

 bed we secured a perfect valve of Leda parvula. (I may say that in 

 this district marine shells are frequent in certain parts up to 700 feet 

 above sea-level. See suppl. to vol. xi, Trans. Geol. Soc. Glasgow, 

 p. 59.) 



The boulders in the sections of the railway at this part are 

 a variety of porphyrites (igneous rocks with conspicuous felspar, a 

 'Surve}"-' term), amygdaloids, felstones (igneous fine-grained rock, 

 s, ' Survey' term), sandstones, dolerites, a few limestones; Matstone 

 Hill granite, a moderately coarse-grained reddish granite, being not 

 infrequent, the parent rock occurring fully two miles to the south 

 and on the opposite side of the Irvine Valley to the railway sections. 



Not only the Boulder-clay, hut a sharp grey sand bed also shows 

 very distinct jointing. The joints in a sand-pit 200 yards north of the 

 railway were very conspicuous, and had attracted the attention of 

 the workmen in the pit, who called them water-haclcs. Workmen's 



