Haworth on the Archccan Geology of Missouri. 373 
The classification was based on the idea that there was a 
marked difference between the structure of pre-Tertiary rocks 
and those younger. It was beHeved, for example, that the 
granite and gabbros were of pre-Tertiary age, and that all rocks 
as young as the Tertiary which were similar to them in chemical 
composition differed from them materially in structure, being 
much less perfectly crystalline. 
In 1874 Prof. J. W. Judd^ published a long paper, on the 
secondary rocks of Scotland, in which he showed that the 
granites, and gabbros of Lyke, Mull and other points were of 
Tertiary age, and that they graded into the overlying volcanic 
rocks which were glassy, the degree of crystallization varying 
with the depth below the surface at which the rock mass solidi- 
fied. In 1876 he published^ a paper of similar import concerning 
the rocks of Shemnitz, Hungary. 
In Feb., 1S85, Messrs. Arnold Hague and J. P. Iddings^ pub- 
lished their paper. On the develoftnent of cfystallization in the 
igneous rocks of Washoe^ Nevada., in vs^hich they showed that 
the structure of the rocks varied with the depth, and that the 
deep seated ones, iDreviously called Archaean, were of the same 
age as those near the surface which had been- called much 
younger. In the same year Prof. Alfred Steltzner* published 
his work entitled: " Beitrage zur Geologic und Palaeontologie 
der Argentinische Republic," in which he describes four different 
localities in the Andes mountains near the boundary between 
Chili and the Argentine Republic that show gradual transitions 
from the holocrystalline rocks, such as granites and diorytes, 
into andesitic lavas, tuffs, and breccia. It should be noted that 
his field work was done from 1S71, to 1874. In February, j 886, 
Prof. Judd^ published a long paper reviewing those published by 
him in 1874 and 1876, and adding considerable evidence to the 
views therein expressed. 
1 Quart. Jour. Geol. Soc, 1874, vol. 30, pp. 220-303. 
2 Quart. Jour. Geol. Soc, 1876, vol. 32, pp. 292-324. 
3 U. S. Geol. Survey, Bull. 17. 
* Title as above, i, Geologische Theil., pp. 19S-213, Cassel und Berlin. 
The book was reviewed by Prof . G. II. Williams in Am. J. Sci,. vol. 33, 
pp. 315-316. 
'•> Quart. Journ. Geol. Soc, vol. 42, pp. 49-97. 
