Mr. Bubble's Synopsis of the Newcastle Coal Field. 217 



By referring to the descriptive notes and sections which accompany 

 this Paper, it will be seen that the several seams vary, not only in thick- 

 ness and character in different parts, but also in quantity ; and it is 

 perhaps not unimportant to remark, that almost all of the seams of 

 Coal become more or less deteriorated in quality, whenever Sandstone 

 happens to form their immediate roof, generally a thin stratum of Clay 

 slate interposes between a Sandstone roof and the Coal, and the deteri- 

 oration of the Coal is in some degree proportionable to the thickness of 

 the interposing clay-slate, that is to say, the thicker it is, the less is 

 the degree of deterioration, and vice versa ; but the degree of dete- 

 rioration is always greatest when the Sandstone forms the immediate 

 roof of the seam, and is in actual contact with the Coal. 



Besides being deteriorated by a Sandstone roof, the Coal is almost 

 invariably more or less intermixed with Iron Pyrites under such a 

 roof. Indeed I consider Iron Pyrites a regular concomitant of a Sand- 

 stone roof. I merely mention this incidentally, as the roof stones of 

 our seams of Coal will probably become the subject of a future paper. 



The country embraced in the table, extends over only what I con- 

 sider to be, strictly speaking, the Newcastle Coal Field. That is to say, 

 it only includes those collieries which now ship, or ever have shipped 

 their coals on the rivers Tyne and Wear, and at Hartley and Blyth. I 

 look forward to the labours of those members of the Society to whom 

 may be confided the construction of the Geological Map, for a more de- 

 tailed and extended developement of the subject to which this Memoir 

 may merely be considered the precursor. 



The Sections of the Strata which accompany this Memoir, and for the 

 construction of which I am indebted to the talent and industry of Mr. 

 Williamson Pjeile, are intended to illustrate the Synoptical Table. 

 They may also be considered as a specimen of the sections which will 

 be required to illustrate the proposed Geological Map of the district. 

 I shall afterwards give a set of sections to a scale from actual admea- 

 surement of the several seams as they are found in the districts con- 

 tained in the table. 



