﻿Charcoal im^^regnated tvitli Slag. 35 



americana). The texture was found to be very harsh and 

 rouo-h. A transverse fissure was found to be filled with 

 a somewhat protruding mass of vitreous matter which 

 also extended above and below wherever longitudinal 

 fractures occurred. Upon handling the specimen, small 

 vitreous particles, like small shot, but usually imperfectly 

 rounded and quite glossy, would detach themselves from 

 the mass. Kunning longitudinally, and clearly lying 

 within the vessels, were to be seen numerous siliceous 

 rods. Where these entered the transverse fissures pre- 

 viously referred to, they^ in some cases, presented free 

 terminations, or again were fused together into a more or 

 less continuous mass. The transverse fracture of the coal 

 is somewhat lustrous, and shows numerous short, black 

 and glossy filaments with a lustrous fracture, projecting 

 from the various vessels. 



The sample of residue sent me shows that when the 

 coal is consumed it leaves behind a rather compact, 

 fibrous mass of stiff, greyish filaments which, when undis- 

 turbed, have the general aspect of a very poor and coarse 

 fibred asbestos. Under a low magnifying glass, the 

 filaments appear as glistening and chiefly transparent or 

 translucent glass rods. They are of very variable size, 

 and in our specimen reach a length of upwards of 30 

 mm., though there is no reason to suppose that they may 

 not have a greater length. The surface shows conspicuous 

 irregularities, which at once serve to suggest the con- 

 formation of the rods to the walls of the vessels in which 

 they occur. 



A more critical examination under a compound 

 microscope shows that the filaments measure from 29 ^. to 

 72 ^. in diameter. For the most part they are perfectly 

 transparent, glass like bodies, or again they assume a 

 yellowish hue, or even become blackish or more or less 

 opaque in consequence of the inclusion of numerous small 

 air bubbles, or of black granules, apparently particles of 



