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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Mar. 9, 



ducing the supposed downthrow, may have left the bed, and thus 

 caused the appearance of the vein running in the former course of 

 the bed along the line of fault, and also the greater regularity of the 

 bed beyond the " Jog." This explanation is represented m fig. 7. 



Fig. 6. Ideal representation 

 of the cause of the appear- 

 ances at Albert Mine. 



Fig. 7. The "Jog'' at Albert 

 Mine, and its supposed rela- 

 tion to the line of fault. 



Part II. [^Abstract.'] 



The author then proceeds to describe the character of the mineral in 

 detail. He considers it, not without doubt, as Pitch-coal. He gives 

 comparative examinations of it and of Jet from Whitby, and shows a 

 similarity of constitution which he considers to indicate similarity of 

 origin. Mr. Dawson has not been able to detect organic structure in 

 it under the microscope*, though such are stated to occur by Mr. 

 Bacon of Boston. 



Respecting its origin and mode of formation, he remarks that two 

 alternatives present themselves : — 1 . The substance may have resulted 

 from a hardening of bitumen, the mode of formation being similar to 

 that of asphaltum : 2. It may, like jet and other coals, have resulted 

 from the bituminization of woody matter under the long-continued 

 action of moisture and pressure. 



He discusses the probabilities of each hypothesis, and remarks that 

 each is accompanied by serious difficulties. After a careful considera- 

 tion of the circumstances of the case, he adheres to the second view, 

 not, however, without hesitation. 



* Professor Quekett, of the Royal College of Surgeons, has kindly supplied the 

 following Note : — 



I have examined many specimens of the jet-like substance from the Albert 

 Mine, Hilsborough, and can find no trace whatever of vegetable structure in them. 

 Fractured pieces of this substance present some peculiar characters, having an ex- 

 ceedingly thin edge from which numerous sharp spicula project, such as are seen 

 sometimes in fractm-ed glass. These spicula are of various sizes and lengths, and 

 are evidently composed of the same material as the mass from which they are 

 given off. There is a great tendency even in the prepared slices to split up into 

 these spiculate bodies, the ends of which are frequently divisible into still finer 

 filaments. 



