Haworth on the Arckcean Geology of Missouri. 283 
B. Statement of Wokk. 
It is attempted in the present paper to give the results of a 
reconnaissance of the Archaean area in jMissouri, and a some- 
what detailed petrographical description of a j^ortion of the mas- 
sive rocks occurring therein. There is such an inter-dependence 
between the field relations of crystalline rocks and their micro- 
scopical and chemical properties that, in order to gain a complete 
understanding of the geology of any territory, one must alter- 
nate field observations with microscopical and chemical studies. 
The field work cannot be carried very far in advance of the 
laboratory investigations, neither can one draw correct conclu- 
sions from the latter if they are not accompanied by extensive 
and accurate field observations. No work of this character has 
before been attempted in the Missouri Archican. From the 
very necessities of the case, therefore, this paper must be of a 
preliminary nature. It is hoped that in the near future circum- 
stances will permit a continuation of the work thus begun in this 
Interesting field. The information used as a basis for the pres- 
ent paper was obtamed partly from others, but principally from 
observations made in the field during the summer of 1SS6, and 
the subsequent examination of materials collected. ]Mr. Richard 
Payne, of Madison county, has sent me over a hundred hand 
specimens from localities not visited by myself. Prof. G. C. 
Broadhead, formerly state geologist, has also kindly loaned me 
portions of his private collection of rocks from this locality. 
Individually I traveled over considerable portions of Iron, Mad- 
ison, and Waj-nc counties, going as far north as Bismarck, as 
far east as Isline La Motte, as far south as Piechnont, and as far 
west as the northeast corner of Reynolds county. Special ef- 
forts were made to collect tvpical specimens of ail the massive 
rocks, whatever they might be. 
In the laboratory investigations I have been assisted by Mr. 
Charles E. Coats, of Baltimore, Md., who kindly made a silica 
determination of the quartz-diabase described later by Prof. C. 
R. Van Hise, of Madison, Wis., who gave me valuable suggcst- 
ons regarding the microscopic character of a large number of 
thin sections sent him; but far more extensively by Prof. G. H. 
Williams, of the Johns Hopkins Universit}', in whose laboratory 
