240 MINERALOGY AND LITHOLOGY. 
ered or illustrated. In the thin section of the sandstone are seen frag- 
ments of quartz, apparently two kinds of plagioclase, orthoclase, decom- 
posed hornblende, biotite, and magnetite. The grains of all are round 
or angular, and are packed together at hap-hazard, and the interspaces 
are empty or filled with dirt. In no case do the constituent fragments 
modify their forms to fill the spaces. All the grains are coated with red 
oxide of iron, which cements them together and determines the color 
of the rock. Further mineral constituents are also found in this same 
section, which are not represented in the figure;—for example: bits of 
microcline, decomposed muscovite, scales of hematite, and chlorite can 
be identified, and calcite, in one place, forms a part of the cementing 
material. 
In New Hampshire, all former fragmental deposits have been so 
pressed, softened, and recrystallized, that all marks of a loose open-work 
of cemented grains have been obliterated, and all the material has 
been brought into its most compact condition. The process by which 
this has been effected has been one of the prominent subjects that has 
been studied and illustrated in this work. 
All those loose deposits which constitute the glacial drift, terraces, 
gravel, sand, clay, soil, etc., are classified as fragmental rocks. These 
materials are, however, so fully discussed under the head of Surface 
Geology, by Prof. Hitchcock and Mr. Upham, that anything more than 
a reference to their chapters is unnecessary. 
MINERALS AS ROCKS. 
In order to render repetition unnecessary, anything that I had to say 
on simple rocks was included in the chapter on Mineralogy, in which 
some remarks will be found concerning limestone, soapstone, and talc 
schist, beds of various ores, the quartzite that is so abundant in veins, 
the beds of infusorial earths, and whatever other minerals in New 
Hampshire are aggregated in such amounts as to form geological 
features. The subject may therefore be dismissed at this point, for, 
though necessarily incomplete, all that has been accomplished has 
been stated. 
* * * * * * * * * 
Conclusion. In a retrospect of the course that has been followed in 
