Description of Mexican Coat. •■ 2?>' 



dertakings, the subject of fuel becomes one of the greatest im- 

 portance. The woods and forests, which once clothed the sides 

 of the Cordilleras in the vicinity of the principal mines, have 

 been, for many years, gradually diminishing, and in many places 

 have totally disappeared; while the Mexican proprietors, with 

 singular negligence, have forgotten to form new plantations to 

 supply that enormous quantity of fuel necessary for the mines. 



The existence of Coal on the mining provinces of Mexico has 

 hitherto been very doubtful. Humboldt, indeed, mentions it has 

 been found in New Mexico ; and that the formations of basalt 

 and amygdaloid on the estates of the Count de Regla might lead 

 to the belief that this substance also would probably be discovered ; 

 a supposition likewise entertained by Mr. John Taylor, whose 

 practical and scientific knowledge of mining is well-known. 

 These opinions are now completely verified ; as among the mineral 

 productions brought by Mr. Bullock from Mexico, are specimens 

 of a coal analogous to jet, which he procured while residing in 

 the vicinity of Real del Monte. A small piece of this substance, 

 weighing sixteen grains, has been analyzed by Dr. Trail, and the 

 result of his experiments, contained in a letter to Mr. Swainson, 

 is expressed in the following words : — 



*♦ This specimen is more analogous to jet than to our Wigan 

 Cannel coal. Its colour is deep brownish black ; its lustre resi- 

 nous ; its cross fracture conchoidal ; its longitudinal fracture has 

 a slightly fibrous appearance, as if it had originally been wood. 

 Its hardness is about that of Cannel coal, as is its frangibility ; 

 but its lustre is higher. The mean of three careful experiments 

 gave its specific gravity zi 1.2248. It becomes considerably elec- 

 tric by friction; in this character it is analogous to jet, and 

 diflFers from Cannel coal, which scarcely shews any symptoms of 

 electricity by friction. Though I have observed that some pieces 

 of the latter slightly moved an insulated cat's hair, which is 

 a very delicate electroscope. Kirwan considers the difference 

 between jet and Cannel in their electric energies, as a diagnostic 

 mark. 



^< It burns with a lively fiame, and gives out much liquid 



