426 rp:port of national museum, 1899. 



when exposed to the air. They occur in beds under conditions similar 

 to the true coals, but are of more recent origin. The liguitic coals of 

 the negions of the United States west of the Mississippi River are mainly 

 of Laramie (Upper Cretaceous) age, and often show easily recognizable 

 traces of their organic origin, such as compressed and flattened stems 

 and trunks of trees with traces of woody fiber (Specimen No. 4795, 

 U.S.N.M.). 



Jet is a resinous, coal-black variety of lignite sufl[iciently dense to be 

 carved into small ornaments (Specimens Nos. 62930, 62804, U.S.N.M.). 

 According to Professor Phillips, it is simply a coniferous wood, and 

 still shows the characteristic structure under the microscope. It has 

 been known since early British times, having at first been found on 

 the seashore at Whitby and other places. The largest seam on record 

 was obtained from the North Bats, near Whitby. It weighed some 

 5,180 pounds and was valued at about $1,250. The material is now 

 regularly rained both in the clifts and inland, and is one of the most 

 valuable products of the Yorkshire coast. ^ 



Bituminous Coals. — Under this name are included a series of com- 

 pact and brittle products in which no traces of organic remains are to be 

 seen on casual inspection, but which under the microscope often show 

 traces of woody fiber, spores of lycopods, etc. These coals are usually 

 of a brown to black color, with a brown or gray-brown streak, break- 

 ing with a cubical or conchoidal fracture, and burning readily with a 

 yellow, smoky flame. They contain from 85 to 75 per cent of fixed 

 carbon, 18 to 60 per cent of volatile matter, from 2 to 20 per cent of 

 water, and only too frequently show traces of sulphur, due to included 

 iron pyrites. Several varieties of bituminous coals are recognized, 

 the distinctions being based upon their manner of burning. Coking 

 coals are so called from the facility with which they may be made to 

 yield coke. Such give a yellow flame in burning and make a hot fire. 

 (Specimens Nos. 55490, U.S.N.M., Connellsville, Pennsylvania, and 

 59260, U.S.N.M., from New River, West Virginia.) Other varie- 

 ties of apparently the same composition and general physical proper- 

 ties can not for some unexplained reason be made to yiekl coke, and 

 are known as noncoking eoah. (Specimens Nos. 59428, U.S.N.M., 

 from Vigo County, Indiana, and 59208, U.S.N.M. (splint coal), from 

 Fayette County, West Virginia.) Cannel coal has a very compact 

 structure, breaks with a conchoidal fracture, has a dull luster, ignites 

 easily, and burns with a yellow flame. It does not coke. Its chief 

 characteristic is the large amount of volatile matter given oft' when 

 heated, whereby it is rendered of particular value for making gas. 

 (Specimens Nos. 56280, 56284, and 58496, U.S.N.M., are characteristic.) 

 Before the discovery of petroleum it was used for the distillation of 

 oils. Below is given the composition of a (I) coking coal from the 



^ Geology of England and Wales, p. 278. 



