240 MINERALOGY AND LITIIOLOGY. 



ercd 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 ot 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 j^lacc, 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 quartzitc 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. 



Concliisioii. In a retrospect of the course that has been followed in 



