THE ORIGIN OF CERTAIN PALEOZOIC SEDIMENTS 243 
careous algae accumulated on the gently sloping bottom of the sea. 
When in their original position these pebbles were all flat and 
parallel to the bottom; in other words they lay parallel to the bed- 
ding planes. At periodic intervals these beds of calcareous mud 
and intermingled pebbles slumped or slid along the bottom under 
the influence of gravity. At the time of the slump or slide the 
matrix around the pebbles consisted of incoherent lime mud or 
paste. As it moved it developed unsymmetrical waves or ripples 
Fic. 4.—Diagram illustrating the arrangement of the pebbles shown in Fig. 3. 
The conglomerate bed is 6 inches thick and the distance from crest to crest of the 
wavelike structures is 9} inches. 
in its mass, just as a thin sheet of water develops ripples as it flows 
down a smooth, gently sloping surface. The whole layer of sediment 
when it finally came to rest—and the whole distance moved may have 
been only a few inches or possibly a few feet—settled into a uniform 
layer once more, but the inclosed pebble-like structures had been 
moved from their original horizontal position, and occurred at all 
angles with the original bedding planes. In these new positions, 
surrounded by the matrix of lime mud, they were in perfect equilib- 
rium and there they remained until the lime mud became trans- 
formed into limestone. And there we find them today when 
