76 History of Hingham. 



In all these cases it may in a sense be called growth, but there 

 is no relation between it and the growth of animals and plants. 

 It is increase by additions to the surface. 



Thus far mineral bodies have been mentioned. The rocks of the 

 earth are generally composed of aggregations of minerals, as 

 Granite, of Quartz, Orthoclase, and Mica ; and Diorite, of Oligoclase 

 and Hornblende. 



Let us now consider briefly what a mineral species is. 



A mineral is a homogeneous, inorganic substance, either simple 

 in containing but one element, as Sulphur, Carbon, Gold, Iron, 

 Copper, Quicksilver, and the other native metals, or a compound 

 of elements which have been united bv laws as immutable as those 

 that govern the motions of the planets, or any others that act in 

 the universe. To recognize this clearly is to awaken an interest 

 in inorganic matter that tends to enlarge one's conceptions of the 

 whole material world. The writer will refer to one or two mineral 

 bodies as illustrations of the law of combinations. 



Quartz is a compound of two elements, Silicon and Oxygen, 

 united in the proportion of three atoms of Oxygen to one of Sili- 

 con, and these proportions never vary. The resultant substance, 

 Quartz, or pure Silica, can and does unite as an acid with very 

 many bases, which in relation to it act as alkalies, forming the 

 greater portion of all known minerals ; and these unions are 

 always governed by the law of definite proportions. 



Take Carbon. This appears as a native mineral in the Dia- 

 mond ; but it appears also combined with Oxygen, forming Car- 

 bonic Acid, in the proportion of one atom of Carbon to two of 

 Oxygen. This Carbonic Acid, in its turn, unites with a large 

 number of basic substances, forming carbonates of Iron, Copper, 

 and very many others, always in definite proportions. Nothing 

 more can be said here of the chemical unions by which minerals 

 are produced ; but something must be added relative to the law 

 of crystallization, by which particles of the mineral as formed are 

 drawn together, and led to arrange themselves in crystals such 

 as we see in nature. No one can behold these beautiful objects 

 without admiration, and this is greatly increased in those who 

 know something of the forces which lead to their development. 

 Crystals of the mineral species have been rightly characterized 

 as the flowers of the inorganic world. To have some idea of their 

 formation, let the reader's mind consider the phenomena attend- 

 ing the cooling of a hot saturated solution of any salt. As the 

 water loses its heat, the particles of salt, in forming, will at once 

 by attraction be drawn together, and the molecules will arrange 

 themselves by the law of crystallization in well-defined forms, — 

 if common salt, in cubes ; if alum, in octahedrons. If the water 

 contains several salts, one will be found generally to have a ten- 

 dency to crystallize before the others, and may be thus formed 

 about any substance placed in the solution ; and subsequently crys- 



