172 Orvjin of Flint. 



with some so small that a microscope is required to see their perfection ; 

 while other specimens resemble siliceous sinter, the depfisition of ther- 

 mal springs. But as I have already said, no indication of thermal 

 springs have been found here, and Professor Klippart has made a mic- 

 roscopic examination of this Flint- Ridge silcx, and can find no ap))earance 

 of diatoms in it. His microscope is a powerful one, the same used for 

 years by Agassiz and Lesquercux, in their studies of the hidden secrets 

 of plant and animal life — investigations that have made their names 

 known and honored in the whole world of science. 



Silicon, the base of silica, is one of the elementary substances of the 

 globe, nearly allied to boron and carbon in some of its properties, and, 

 next in abundance to oxygen, is unknown in nature in its pure state, 

 but, combined with oxygen, forms silica or quartz. Although infusi- 

 ble and insoluble, many oxides enable heat to melt it down and form 

 glass ; or, if but a trace of alknli be contained in waters, those Avaters, 

 if heated, have the power of dissolving it, and thus dissolved it may 

 spread widely, either to enter new combinations or to fill with quartz 

 fissures and cavities among the rocks, thereby making veins, and act 

 ing as a general current and solidifier. As an elementary principle in 

 nature it is found everywhere in proper combination with oxygen, con- 

 stituting rocks; again, taking part in the construction of plants; asso- 

 ciated Avith oxygen, hydrogen and with alkalies in silicifiied water ; and 

 with nitrogen, oxygen, carbonic acid, and other constituent properties, 

 that make up the gaseous envelope surrounding the earth — the atmos- 

 phere which is directly or indirectly the cause of numerous geological 

 observations — the great laboratory in which all meteorological and 

 electrical phenomena are elaborated. In this combination silica ascends 

 and descends with all aqueous and gaseous vapors, while contributing 

 its share to the composition of all organic as well as inorganic substances. 



The genei-al theorv has been that all the later siliceous deposits owe 

 their origin to the breaking up, attrituration and destruction of pre- 

 viously formed rocks, and that all sandstones and conglomerates are 

 thus prepared, transported by water, distributed and deposited where 

 we now find them. But this theory is being somewhat modified by 

 such scientists as Sterry Hunt, Beaumont, and some others, who con- 

 clude that more credit should be given to chemical and less to 

 mechanical action in the formation of sedimentary rocks ; and that 

 beside thermal springs many waters contain a large proportion of dis- 

 solved silica. Hunt says : " The large proportion of dissolved silica 

 which many waters contain appears in sedimentary deposits, not only 

 replacing fossils, and forming concretions and beds of flint, chert, and 

 jasper, but also in a crystalline state, as is seen in the crystalline quartz 



