Haworvu. | Physical Properties of the Tertiary. 269 
frequently of from four to six or even eight to ten inches in diameter, 
and possibly much larger. In the beds of clay and in sand beds 
where the supply of cement seems to have been limited odd shaped 
masses are often produced. The concretionary granules assume the 
shapes of common concretions, rounded, spherical, oblong, and 
irregular. Plate XLI is a reproduction natural size from a photo- 
eraph of such nodules gathered in the northeastern part of Logan 
county. Frequently instead of producing the somewhat rounded 
nodular concretions elongated masses extending up and down are 
formed, sometimes with radiating lines reaching in different direc- 
tions as though water containing calcium carbonate in solution 
in working its way downward through the beds of clay found more 
ready channels there than elsewhere. Plate XLII is from the photo- 
graph of a clay bank in the southern part of Sheridan county on 
one of the tributaries of the Saline river. It is similar to those found 
over the whole country. The granules of sand and particles of 
clay in such cases are held together with a firmness approaching 
that of the mortar beds themselves. Mr. Crane, who spent the 
greater part of two summers in the northwestern part of the state, 
in describing the forms assumed by such concretionary masses 
likened them to the results we might expect were large quantities 
of molasses poured upon beds of sand and clay and allowed to work 
its way downward through whatever channel or more porous areas 
it might find. This somewhat homely illustration perhaps is as 
good as can be given. The elongated direction is by no means 
always vertical. Bifurcations and trifureations in the mass are 
frequent and different vertical masses are frequently connected by 
radiating lines as though there was a connection between the de- 
positing agents in the different channels. 
A. microscopic examination of the white masses which are thus 
firmly cemented shows that the calcium carbonate exists princi- 
pally as well formed crystals usually of aragonite. The thinner 
beds of such deposits generally are not held together very firmly 
but are loose almost like sand. The aragonite crystals in such 
cases are usually small, frequently measuring no more than 1-500 of 
an inch in diameter. Rhombolic calcite crystals are also found, but 
not so abundantly as the aragonite crystals. The larger masses 
