Mineralogy. 77 



tals of the others will form upon the first and adhere to it, and 

 these in turn will have others added to them. 



Let us now consider what has heen going on in nature. Fis- 

 sures have been formed, by earthquake action or otherwise, extend- 

 ing upwards through the rocky strata ; and the hot waters of 

 thermal springs, holding in solution mineral elements dissolved 

 from the rocks in deep recesses of the earth, have risen upwards, 

 and losing more or less of their heat as they passed through the 

 colder rocks towards the surface, have deposited minerals upon 

 the. walls, one species often succeeding another. Thus were de- 

 posited the magnificent crystallizations of Quartz, Fluor Spar, 

 Galena, Carbonate of Lime, and other species from Cumberland and 

 Derbyshire in Great Britain, specimens of which may be seen in 

 the Hingham Public Library. 



Minerals are not only found to have been produced in liquid 

 solutions containing their elements, but they are also produced 

 whenever a molten condition of matter allows of the free move- 

 ment of its particles ; consequently the elements of an igneous 

 rock, as they cool in coming to the surface, will tend to aggre- 

 gate themselves according to their chemical affinities, and to 

 arrange themselves in crystals ; but the cooling being generally too 

 rapid for this, we have, as in granite, only an aggregation of im- 

 perfect crystals. 



With these very general remarks upon minerals, intended only 

 as a very partial presentation of the matter, the writer will call 

 attention to the few that are found in Hingham. The larger 

 portion of these have been already mentioned in the Geology 

 of the town as constituents of the rocks, namely, Quartz, Mica, 

 Hornblende, Augite, Orthoclase, and Oligoclase. 



Quartz may be otherwise referred to than as a component part 

 of a rock, as it appears forming veins in every part of the town ; 

 and in cavities of these veins have been found some beautiful but 

 small crystals of Amethyst, which is a variety of Quartz. 



Jasper, another variety of the same mineral species, is found 

 at Rocky Neck, as stated in the Geology of that locality. 



Other minerals, not of the Quartz family, are — 



Pyrite (Sulphide of Iron), which often appears in small cubic 

 crystals in the Trap rocks. 



Chalcopyrite (Sulphide of Copper), which has been found dis- 

 seminated in a vein of Quartz. 



Molybdenite (Sulphide of Molybdenum), observed in small scales 

 in granite blasted from a ledu - e on the line of the Nantasket Rail- 

 road, near Weir River. 



Epidotc, often found at and near the junction of Trap with 

 Granite, sometimes exhibiting slight crystallization. It also 

 occurs, of an impure character, in veins at Rocky Neck. 



Calcite (Carbonate of Lime), found in digging a ditch on the 

 line of and near Burton's Lane, where some rock was blasted 



