Sioux City Academy of Science and Letters. 171 
was the bed, but upon exposure to sunlight and air its 
jointed structure appears at right angles to the bedding, 
and along the joint and bedding planes the material is 
easily separated by hand into small cubes and rectangu- 
lar prisms. These individual fragments do not become 
relatively softer, but they can easily be cut with a knife, 
and are much more easily crushed and ground than frag- 
ments of bituminous coal. 
The lignite cleaves, where of a woody structure, in 
the direction of the grain, and also in the direction of the 
bedding planes, and has a rough, uneven fracture. 
When the material has given up the greater part of 
its moisture to dry air, the consequent shrinkage of the 
particles and opening up of joints causes the material to 
lose its cohesiveness and to fall to pieces at the slightest 
jar. If exposed again to moist air, the movement be- 
tween the particles consequent upon the rapid absorp- 
tion of water still further aids the disintegration of the 
mass, so that after a few alterations of drying and wet- 
ting it can be carried only in dust-tight receptacles. 
On plunging an air-dried piece of the lignite under 
water, a rapid rise of bubbles—almost an efferves cence— 
of the gases held within the cracks and pores of the 
material is immediate, and of the softer pieces when wet 
few fail to fall to pieces like lumps of softened mud. 
The specific gravity ranges between 1.28 and 1.35 for 
air-dried samples which is comparatively high for such a 
soft, loose material, but is accounted for by the presence 
of a high percentage of incombustible mineral matter, the 
ash of the chemical analysis. 
SYNOPSIS OF TABLES SHOWING PHYSICAL PROPERTIES AND 
CHEMICAL COMPOSITION: 
Table I. Physical properties of lignites. 
“If. Proximate analyses of Dakota County lignites. 
“ Ill. Proximate analyses of other lignites. 
“TV. Proximate analyses of lignites and coals (comparative). 
“VV. Ultimate analyses of Nebraska and Wyoming lignites. 
“VI. Ultimate analyses of lignites and coals (comparative). 
“VII. Caloric power of Nebraska and Wyoming lignites. 
“VIII. Calorific power of other lignites and coals (comparative). 
“IX. Gas producing capacity of Nebraska and Wyoming lignites. 
“_-X. Gas producing capacity of other lignites and coals (compar- 
ative). 
