192 



than in tlie Esk basin, arising chiefly from the sandstones and coals 

 thinning away towards the east. 



The strata on the west side of the Esk basin, dip to the east and 

 south-east at a very steep angle, and are in some places absolutely 

 vertical. On the opposite or east side of the Esk basin, they 

 slope to the west at an angle varying from 20° to 40°. 



The strata on the west side of the 7y?«e basin dip to the east, at 

 an angle varying from 15° to 20° ; and on the opposite or east side 

 of the same basin, theydip to the west at an angle of only 3° or 6°. 



In the intervening ridge which runs from Prestonpans to the 

 Roman Camp, the strata mantle over from the one basin into the 

 other, and are there occasionally broken so as to shew an anti- 

 clinal line. 



The different kinds of coal were described ; and it was stated, 

 that each kind was characterized by differences in the fissures or 

 joints intersecting them. 



The principal slips in the district were next pointed out ; and 

 the author referred to a table he had constructed, shewing the di- 

 rection of each, and the amount of dislocation produced on the in- 

 tersected strata. Between eighty and ninety of these were also 

 laid down on the map accompanying the memoir. 



In describing the unstratified rocks of the district, the author 

 mentioned, there were no hills or amorphous masses of trap within 

 the proper limits of the Lotliian coal-field ; and that the trap shewed 

 itself only in dykes, which run in straight lines intersecting the 

 strata. He pointed out three or four such dykes, varying from 60 

 to 120 feet in width, — all of which appeared gradually to thicken 

 towards the west, and all of which run in nearly an east and west 

 dii'ection. 



3. The following Memorandum was communicated by Pro- 

 fessor Forbes. 



" A series of delicate and tedious experiments on heat have con- 

 ducted me to the following results, which will be fully discussed in 

 a paper shortly to be laid before the Society. 



" 1. An entire confirmation of my previous statement, that diffe- 

 rent kinds of heat are differently susceptible of polarization by 

 transmission through a given bundle of mica plates ; heat from ob- 

 scure sources being less polarizable than that from luminous sources. 

 I considered my investigations incomplete untU I had proved not 

 only that my former experiments had led me to correct results, but 



