44 HOFFMANN ON HYGROSCOPICITY 



2. The Lignitic Coals show a greater disposition to resist ^ exposure to the air — being, 

 on the whole, tolerably firm ; contain much less water ; do not impart so deep a coloration 

 to a solution of caustic potash ; show (by fast coking) a slight caking tendency, and in 

 regard to chemical composition, occxipy a position between true lignites aud true bitu- 

 minous coals. 



3. Whilst the Coals resist exposure to the air ; are hard and firm ; contain but a small 

 proportion of water; communicate but a very slight, if any, coloration to a solution of 

 caustic potash; yield (by fast coking), in the majority of instances, a good firm coke, and 

 in respect to general appearance and chemical composition closely resemble some varie- 

 ties of coal of the Carboniferous system. 



' Employed, throughout this paper, in the sense of "not breaking down." 



NOTES TO TABLE. 



(1.) That is to say the amount of water retained by the same after exposure to a perfectly dry atmosphere for 

 35-1 hours. 



(2.) The treatment witli solution of caustic potash was conducted at the ordinary temperature. This offers 

 Some advantages over that by digestion at a boiling heat — the action not being fo energetic (although sutticiently 

 so, as the results show, to obtain the desired result), a greater number of shades of color are obtained, thus admitting 

 of a more accurate estimate of the nature of the fuel. The experiments were all carried out simultaneously, and 

 under precisely similar conditions ; the results admit, therefore, of a fair comparison. The fuels were all reduced 

 to a very tine powder; specific gravity of the potash solution, 1"I6 ; time of contact, shaking at intervals, two 

 hours; after which filtration was proceeded with, the filtrates being collected in flat, broad-fared, narrow-sided 

 white-glass bottles of uniform dimensions. The amount of alkaline solution, and weight of fuel employed, was in 

 all instances the same. 



(3.) In appearance it resembles some varieties of coal of the Carboniferous system. 



(4.) Is probably an extension of the seam at Blackfoot Crossing, Bow River (specimen No. 23). 



(5.) This specimen had been kept in the show-cases of the Museum for years, and may fairly be regarded as, 

 having been in a thoroughly air-dried condition. 



(G.) This lignite contains an occassional interstratifîed layer of mineral charcoal, likewise thin plates of gypsum 

 and numerous minute crystalline aggregations of pyrite ; it also had a large amount of lemon-yellow, occasionally 

 brownish-yellow, subtr.ansparent to transparent resin, chiefly in small particles, ditl'iised through its substance. 



(7.) From the same seam (points of collection, however, differeit) as that from which specimen No. 6 was 

 taken. 



(8.) This "conchoidal" lignite would appear to consist of fragments of the more solid portions — root, trunk, 

 or branch — of some of the vegetable matter from which the bed of lignite has been derived. 



(9.) Specimens Nos. 23 and 28 are from natural exposures of the same seam, the former being about eight, and 

 the latter about six, miles south of tfce shaft. 



(10.) This coal is, here and there, intersected by thin pl.ites of calcite, as also by films of pyrite. 



(11.) This coal is intor.<ected b)' numerous thin plates of gypsum and calcite, and contains, in parts, a few films 

 of pyrite. 



(12.) Specimen No. 46 is from a natural exposure of the same seam on the north side of the river. 



(13.) This coal is intersected by numerous thin plates of calcite, as also, here and there, by a few films of 

 pyrite. 



(14.) This specimen was, in parts, very much soiled with argillaceous matter, and to this circumstance may 

 be attributed the large percentage of incombustible matter which this sample of the fuel was found to contain. 



(15.) The sample received for examination was, in parts, coated with earthy matter which was not readily 

 removable : this would account for the large percentage of ash which this particular specimen was found to leave 

 on ignition. 



