260 MR MILNE ON THE MID-LOTHIAN AND EAST-LOTHIAN COAL-FIELDS. 



(8.) The thickness of the hmestone strata has heen marked on the table at 

 a number of different points. It will be observed, that in the three uppennost 

 limestones (those, viz. which occur about the middle of the series) a veiy remark- 

 able regularity of thickness prevails. The case is quite different with the lime- 

 stone beds in the lower part of the series. The limestone immediately below the 

 North Greens coal, has a very different measure of thickness in some parts of the 

 district from what it has in others. It wiU be seen that, in the north and along 

 the west part of the coal-field, it is only from 4 to 6 feet thick, — too thin to be 

 workable. On the south and east parts of the coal-field, it attains a thickness of 

 20 and 30 feet. It is important to notice, that, in this respect, the limestone at 

 the bottom of the series presents features directly opposite to what is presented 

 by the coal-strata.* 



I have attempted to form a similar table of other strata, comprehending the 

 Sandstones, Shales, and Fire-clays. These are, for the reasons already hinted 

 at, less accurately known than coals and limestones; so that any inferences 

 from the table now referred to are less to be depended on. But I may notice the 

 results which it indicates. 



Some of the shales are so hai'd, arising chiefly from an admixtiu-e of calca- 

 reous matter with which they are impregnated, as to have obtained the popular 

 name of Bastard Limestone. These are, generally speaking, thickest to the south, 

 and are situated in the lowest part of the series. 



(4.) The shales (properly so called) as well as the sandstones are thickest to- 

 wards the north. In the New Mills level (south of Dalkeith) there are six beds of 

 sandstone, each of which has been recognised on the shore between Musselburgh 

 and Portobello. At the foiTuer place, these six beds present an aggregate thick- 

 ness of 284 feet ; at the latter 475 feet. So far in regard to their tendency to 

 thin or thicken towai-ds the south and north parts. In regard to the east and 

 west parts, it would rather seem that the sandstone rocks become thinner to- 

 wards Wallnford and Tranent. 



(5.) In the same section of the New MiUs level, akeady refen-ed to, there 

 happen to be six beds of shale, which have been also recognised at or near Mag- 

 dalen Pans, on the sea-shore. At the former place, they exhibit an aggregate 

 thickness of 181 feet — at the latter of 285 feet — ^being nearly the same rate of 

 increase as the sandstones.f But, on the other hand, this result is in some de- 

 gree compensated by the fact, that the thick beds of bastard limestones which 

 lie almost entirely on the south side of the district, and which are not reckoned 



* The table referred to in the above remarks having been considered too bulky to be published in 

 these Transactions, extracts from it have been put into the Appendix A. 



+ The table from which these results were obtained, has not been published, with this paper, for 

 the reasons applicable to the other table. The data on which it was constructed, were derived, chiefly 

 from sections given by Farey in his valuable report on the Duke of Buccleuch's coal-field. 



