390 RESEARCH IN CHINA. 
concretions; neither does the apparent absence of concretionary structure. Yet, even 
if they be concretions, we are still unable to determine the method of formation, whether 
by chemical solution, diffusion and crystallization within the mass, or by physical absorp- 
tion of extraneous carbonate of lime in colloids. 
With reference to the organic origin of the solid lentils from which the pebbles are 
supposed to be derived, I am inclined to give more weight than Blackwelder attaches to 
the fact that the characteristic conglomerates occur very extensively in Middle and Upper 
Cambrian strata in China, Texas, Indian Territory, and throughout the Appalachians. 
They are also found in older Pre-Cambrian limestones, as well as in younger Paleozoics, 
but not so widely distributed as in the Cambrian, so far as we know. ‘They occasionally 
exhibit a radiate arrangement such as that shown in Plate LII, Fig. E. The cases observed 
are few in comparison with those in which the arrangement is accidental; they may be acci- 
dents of shingling of the flat pebbles; and the fact that some such pebbles are stratified 
supports the view that they were originally laid flat and now occur tilted in consequence 
of disturbance only. But the relations in horizontal plan, shown in Plate LII, Fig. E, do 
not conform to any ready mechanical rearrangement and give foundation to the idea that 
they may represent undisturbed growths radiating irregularly from a common center. In 
that case the discs grew vertically as well as radially, and stood on edge in the mud. 
Each of the hypothetical processes of local induration, above sug- 
gested, is possible, and any one or all of them may, together with others, 
be found to be that from which the conglomerates have resulted in a 
particular locality. 
The individual specumens.—No. 5, from the base of the Ch’au-mi-tién 
formation near Ku-shan. The entire rock is a dense gray limestone with 
a faint olivaceous tinge. The pebbles are thinly coated with earthy hem- 
atite and thus appear red as they weather out upon the surface. 
No. 47, from 30 feet, 9 meters, above the base of the Ch’au-mi-tién 
limestone, in the mountain southwest of Yen-chuang. This is similar 
in most respects to the first, but the matrix is more largely composed 
of small bits of limestone in a crystalline cement of calcite. Although 
the majority of the pebbles show the ferruginous red coating, in some of 
them this feature is entirely absent. There is considerable diversity of 
texture, color, and purity among the various pebbles. Some of them 
contain scattered rhombs of siderite which are more or less completely 
altered to limonite. This mineral is also found in the cement, especially 
in the cavities produced by corrosion of the surfaces of the pebbles. 
No. 46, from the same place as the last, differs from the latter in no 
essential feature. The cement is more ferruginous and the red borders 
are absent from many of the pebbles. 
No. 40, from the lower part of the Man-t’o shales, 4 miles, 6.5 kilo- 
meters, north of Sin-t’ai-hién. The red borders of the pebbles are very 
indistinct in this specimen, and the bright ocher color of the cement indi- 
cates a high percentage of siderite in the unweathered rock, Several of 
