188 Geological Gleanings. 



latter character may be conveniently shewn by the method first 

 pointed out by Von Kobell. A fragment placed in a solution of 

 sulphate of copper (blue vitriol) in contact with a strip of zinc, 

 will become quickly coated with a deposit of metallic copper : a 

 phenomenon not exhibited in the case of common coal. Deduct- 

 ing ash and moisture, true anthracites present, as a mean, the 

 following composition : — Carbon 92^, Hydrogen 3^, Oxygen (with 

 trace of Nitrogen) 4. All yield an amount of coke equal to or 

 exceeding 89 per cent. The coke is frequently pulverulent, 

 never agglutinated. 



The comportment of anthracite before the blowpipe has not 

 hitherto been given in detail. It is as follows : Per se, the assay 

 quickly loses its metallic brilliancy. After continued ignition, 

 small white specks of ash appear on its edges. In borax it dis- 

 solves very slowly, with constant escape of bubbles. It is not at- 

 tacked by salt of phosphorus ; the assay works to the top of the 

 bead and slowly burns away. In carbonate of soda, it effervesces, 

 scintillates, and turns rapidly in the bead ; and the soda is gra- 

 dually absorbed. In the bulb tube a little water is always given 

 off, but without any trace of bituminous matter. 



As regards their geological position, the true anthracites belong 

 chiefly to tbe middle portion of the Palaeozoic series, below the 

 Carboniferous formation ; or otherwise, they constitute the under 

 portion of the coal measures. Frequently also, anthracites occur 

 m the vicinity of erupted rocks, and amongst metamorphic strata, 

 as manifest alterations of ordinary coal. 



2. — Anthracitic Coals. — These are often confounded with the 

 true anthracites, into which indeed, as already stated, they gra- 

 dually merge. Normally, they differ from the true anthracites in 

 being non-conductors of electricity, in burning more easily and 

 with a very evident yellow flame, in yielding a small quantity of 

 bituminous matter when heated in a tube closed at one end, and 

 in furnishing an amount of coke below 80 per cent. The coke is 

 also in general more or less agglutinated, although it never pre- 

 sents the fused, mamillated appearance of that obtained from cak- 

 ing coal. The mean composition, ash and moisture deducted, 

 may be represented as follows : — Carbon 89|, Hydrogen 5, Oxy- 

 gen (with trace of Nitrogen) 5^ ; or Carbon 89, Hydrogen 5, 

 Oxygen (with trace of Nitrogen) 6. 



3. — Caking Coals. — These are often termed, technically, "Fat 

 Coals." They constitute the type-series of the coals, properly so 



