MINERALOGY AND GEOLOGY, 



CHAPTER I. 



MINERAL SUBSTANCES. 



1. Different Forms of Minerals. As solid substances 

 alone are kept in mineral cabinets, minerals are thought 

 of by most people as being only in the solid form. But 

 there are mineral liquids and gases. Mercury is a liquid 

 mineral. Water is a liquid composed of two mineral 

 gases, oxygen and hydrogen. The atmosphere is a mix- 

 ture of three mineral gases oxygen, nitrogen, and car- 

 bonic acid, and holds always in solution some of a min- 

 eral liquid water. All minerals are, in one sense, solid, 

 for the atoms of which liquids and gases are composed 

 are solid. All matter is undoubtedly, as Newton sup- 

 posed, formed of " solid, massy, hard, impenetrable par- 

 ticles" (Partl., 14). 



2. Relation of Heat to the Forms of Matter. The form 

 which many mineral substances assume is dependent 

 upon the degree of temperature to which they are ex- 

 posed. Thus water appears in the three forms solid, 

 liquid, and gaseous, according to the degree of heat. 

 We ordinarily speak of it as a liquid substance, because 

 under all ordinary circumstances it has this form ; but 

 there are localities, as the tops of some mountains and 

 the extreme polar regions, where its ordinary condition 

 is that of a solid. For the same reason, we speak of 

 metals, with the exception of mercury, as solids ; but 

 there was a time, in ages long gone by, as you will see 

 in the geological part of this book, when these metals 



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