GRAVEL AND SHINGLE 299 
water ; both are stratified and both consist of fine particles 
cemented together. Sandstone, as its name implies, is com- 
posed of grains of sand ; Shale, on the other hand, is made 
of fine clay or mud. 
Examine a number of the other specimens and compare 
them as to hardness, texture, fracture, and cleavage. 
Notice the ease with which the laminated specimens 
split into thin leaves along lines of deposit. Note.—Shale 
proper always possesses this laminated and fissile structure. 
As in the case of Sandstones, educe that all these rocks 
are of aqueous origin—are in fact sedimentary rocks. 
Refer to material shaken ‘up in glass jar, most of which 
will be still suspended in the water. Draw attention to 
length of time required for fine material to settle—refer to 
what happened when sand, fine and coarse, and gravel 
were shaken up in jar. Which came to rest first on bottom: 
of jar? Which remained longest in water—and why ? 
Educe that rivers or currents carrying or moving sedi- 
ment along will drop the heavier grains first—i.¢., near the 
shore, and that the finer and lighter particles, taking longer 
to settle, will be carried far from land before coming to 
rest. In this way lead pupils to see that Sandstone was 
laid down in shallow water, relatively near the land, 
whereas Shale or mud rocks were deposited in deep water. 
NoTreE.—Shales present almost endless variety of texture and 
composition, passing on the one hand into Clays, or where much 
hardened into Slates, and on the other hand into Sandstones. 
XTII.—GRAVEL AND SHINGLE. 
Gravel is the name given to water-worn stones, ranging 
in bulk from the size of a small pea to that of a walnut, 
whilst the term shingle is applied to coarser debris 
ranging up to blocks as big as a man’s head or larger. 
