MR MILNK ON THE MID-LOTHIAN AND EAST-LOTHIAN COAL-FIELDS. 317 



The uppermost bed is worked on the west side of the road near JMr Bailey's 

 glass-work. It is of a light blue colour, and easily cut with the spade. Its 

 thickness on the south side of the work, is about 25 feet ; it gets thinner towards 

 the NE., — and at the Edinburgh road, it crops out altogether. 



The second bed of clay which supports the one just described, is worked in 

 the fields between the Edinburgh road and the sea. Near the shore it is only 7 

 or 8 feet thick, but its surface has evidently been lowered there, by the operation 

 of subsequently emerging causes. Near the Edinburgh road, it is 35 feet thick. 

 It appears, however, to get thicker towards the SW., for in sinking a well at Mr 

 Bailey's manufactory on the south side of the road, about 80 feet of clay was 

 gone through before water was reached. The water gushed up fi-om a thin bed 

 of sand. This lower deposit of clay is supposed to be there, from 55 to 60 feet 

 thick. 



It has been ascertained that a bed of gravel lies beneath this fine clay at 

 PortobeUo. I have not been able to discover whether this gravel bed belongs to 

 that member of the series which I have termed the gravel or stoney clay ; — it 

 would appear that about 10 or 12 feet from the top of the lower bed, there is 

 another layer of fine gravel in the clay about 14 inches thick. 



Both the upper and the lower bed of clay at PortobeUo is finely laminated. 

 The layers are not more than one-sixth of an inch in thickness, — in some places, 

 scarcely thicker than the leaves of a book ; — and they separate very easily. This 

 arises from there being a thin film of very pure and attenuated mud and some- 

 times sand, between the lamince. 



This brick clay is thicker at PortobeUo than any other place I know of in 

 the district. At Harden Green it is only 8 feet thick. To the east of Dalkeith 

 it varies from 3 to 13 feet. Near SheriflfhaU engine it is 13 feet thick. It ap- 

 pears to be thickest in those situations where it occupies the lowest level. I do 

 not think it exists at a higher level than 150 feet above the sea. 



I have a strong suspicion that the particular stratum of clay I am now de- 

 scribing is contemporaneous with the Carse clay of Falkirk and Stirling. This 

 Carse clay is partially described by Mr Blackadder in the 5th volume of the Wer- 

 nerian Society's Transactions. My reasons for this opinion, are foimded not merely 

 on the great similarity in the texture of the clay in both districts, but also on 

 the fact of its being covered, as in this district, by layers of sand and gravel. 

 The sand, according to Mr Blackadder's account, in the eastern part of the dis- 

 trict (as about Falku-k) contains pieces of coal, — ^but towards the west, as at Stir- 

 ling, it is entu-ely free from them, and contains pebbles of mica-slate. 



In regard to the existence of this bed of clay in East-Lothian, I have obtain- 

 ed as yet but scanty information. I have found a very similar deposit near the 

 mouth of the Tyne, and extending round the margin of Belhaven Bay. In Bel- 

 haven Bay, this clay is now worked to the depth of 9 or 10 feet. A section of 



