Hints on the Localities of Coal. 4G5 



the bursting of the boiler by forcing cold water into it when 

 allowed by carelessness to become dry, and to get red hot. Metal 

 plugs should always be riveted into such boilers. They should be 

 made of a fusible mixture, that will melt wlienever the contents 

 of the boiler attain a certain degree of heat. This should never 

 be omitted, even when the boiler is of the best form, which cer- 

 tainly is that contrived by Mr. Woolf. Indeed, I think it im- 

 possible to conceive any other arrangement for a boiler possess- 

 ing equal strength and durability, and coiisequently, safety. As 

 it would appear that some of these safeguards are not so ge- 

 nerally known as they ought to be, you may, perhaps, rendev 

 some service to the community by giving them a place iu your 

 useful miscellany. 



I am, sir. 



Your most obedient servant, 



Thomas Gill. 



LXXXVII. Hints on the Localities of Coal. 



To Mr. Tilloch. 



iSiR, — ii-s a spirit of inquiry has lately been excited on the 

 subject of the various localities of coal, the following brief no- 

 tices of the different formations or sets of rocky strata among 

 which it has been detected in the north-east of England, may 

 aiford amusement to such of your readers as pay attention to geo- 

 logical facts, and some useful information to those who suspect 

 that this valuable fossil may lie concealed under beds of stone 

 found on tlieir own estates or royalties. 



1st. Tolerably good seams of coal are spread over that part of 

 Northumberland situated north of the Coquet and west of By- 

 well on the Tyne, with the exception of the porphyritic and 

 grau wacke mountains forming the Cheviots : — here it alternates 

 with sandstones, shales, and blue encrinal limestone, and over- 

 lying niasses or mountain caps of basalt are scattered over the 

 whole country. As the limestone stretches from the sea-shore 

 towards the south-west, and rises into the chain of mountains 

 which reach from Northumberland to Derbyshire, the seams di- 

 minish in thickness, and the coal consists chiefly of carbon and 

 feulphur with a very small proportion of bitumen. Such is the 

 crow coal of Alston Moor. 



2d. The Newcastle coal formation measures 58 miles from 

 Acklington in Northumberland to Cockfield in Durham, and 

 24 miles from the sea-coast at Tynemouth to the neighbourhood 

 of By well. Its strata comprise sandstones and shales, with oc- 



Vol. 4G. No. 212. Dec. 1815. G g casional 



