920 Sand-Boulders in the Drift in Central Missouri. [c 
they are quickly recognized owing to their brighter color, being 
more highly stained red-yellow than the clay, as the coloring- — 
matter appears to have been an after-deposit in the more porous — 
wii! ©. ; 
. Sand-Boulders—Besides the irregular sand-pockets thereare — 
occasional well-formed, rounded boulders of sand, distinctly sepa — 
rated from the clay. Some sections, exposed in the foundations — 
and drains, were two hundred feet or more in length, and tento 
eighteen feet deep, and cut through many sand-boulders. Some 
of the boulders were three to four feet long by one to one and 4 
one-half feet thick (Fig. 4); one was fifteen feet long and three _ 
thick (Fig. 2); another thirty feet by six (Fig. 3); and a right — 
angled segment eighteen feet in diameter was taken out of at- 
other (Figs. 1 and 4), whose thickness was eight feet; but ontop 
of the boulder there was a deposit of fine stratified sand one and 
one-half feet thick. A 
8. Character of the Sand-Boulders—The sand is generally 4 
Coarse (the grains being one to five millimetres in diameter), 
with parallel layers of pebbles (one to two inches in diameter} 
It contains a little clay, which, together with`the surfaces of et ; 
grains, is brightly stained with iron. The boulders usually p 4 
horizontally, but occasionally they are found thrown upon pe ' 
Owing to the general occurrence of sand-pockets and boulder 4 
Scattered through the clay, most of the brick walls built ap 
the clay foundations are liable to crack, as some portion 
rests upon the yielding strata. i 
9. Origin of the Sand-Boulders, and the Subaqueous Ongim ee 
Drift—From the stratified character of the sand-boulders q" 
resting in the clay, and their rounded form, their subat 
origin is manifest. The rounded form is the result of the 
wearing and dissolving away the angularity of masses 0 
sand. The transportation was effected by coast and #9 
ice, into which the sandy masses were frozen. The j 
masses of sand commingled with the clay were depos! m 
