284 Haworth on the Arc/icBan Geology of Missouri. 
the greater portion of these investigations have been conducted. 
It is with pleasure that I make use of the present opportunity to 
express my gratitude to all of the above named gentlemen for 
their kindnesses, and especially to my honored teacher, Prof. 
Williams, who was ever ready to give assistance and advice, and 
to whose untiring inteixst such value as this paper may possess 
is largely due. 
C. General Geology. 
(a) The general geology of the Missouri Archasan is very 
simple. There are no contorted or twisted strata, and no high 
angles of dip showing violent orograj^hic movements. Every 
thing indicates that the movements which have occurred were 
of the most gentle kind. The rocks themselves do not present 
a very great variety. There is a total absence of any thing ap- 
proaching gneiss or schist.' Different kinds of porphyry — 
which is the predominating rock — granite with simple and al- 
most constant mineralogical composition, and dykes of diabase 
and diabase porphyryte constitute nearly all that can be referred 
to the Archican. 
( b ) Rc/afifl/i of stratified to massive rocks. 
Limestones and sandstones occur along the valleys and some- 
times on comparatively high ground throughout almost all of 
the Archccan area. It is probable that from those places where 
granite is exposed in the valleys, as along Stout's creek and the 
St. Francois, the sedimentary rocks have been carried away by 
erosion. Pumpclly- and Broadhead^ — and in fact everyone 
else who has written on the subject — referred the gi'anites and 
porphyries to the Archaean, and the limestone and sandstone to 
the Silurian. In the geological map issued with the 5th An. 
Rep. of the Director of the U. S. G. S, the sedimentary rocks 
' Pumpellj mentions a rock with "schistoid structure," — Mo. Geol. 
Rep., 1872, p. 26 — which he thinks is a limestone changed to porplijry. 
He says: "Here is a member of tiie porphyry series which was unques- 
tionably a limestone, but in which the original phvt-ical and chemical 
characters have almost wholly disappeared," Not having seen such a 
rock I can say nothing about it. 
" Mo. Geol. Rep., 1872. p. 8. 
* Mo. Geol. Rep., 1873-74, p. 347. 
