T. STEKKV HINT. 43-(13) 



other delicate modes of research, we are enabled to de- 

 fect their presence disseminated in solid rocks or dissolved 

 in the ocean's waters, but we find them concentrated in 

 the endogenous rocks. Not to mention silver and gold, 

 copper and tin, which, at once suggest themselves, we 

 there find lithium, caesium, glucinum, yttrium, cerium. 

 zirconium, tantalum, uranium, tungsten, molybdenum, 

 and other rare elements accumulated in such quantities 

 as to make up a large part of certain mineral species 

 peculiar to these endogenous rocks. 



Whence have come these rare elements, and what is 

 the source of the matters which constitute these vein- 

 stones \ As I have said before, the great bulk of an endoge- 

 nous rock may consist of the same elements as a lime- 

 stone, a sandstone, a gneiss or a granite, from which 

 rocks, however they differ, alike by their structure and 

 by the presence of rare and peculiar mineral species. 

 The origin and the composition of these veinstones thus 

 assume a great interest to the student of the physiology 

 of the earth. As the forces at work in a growing plant 

 determine the secretion in one part of its structure of 

 sugar and acids, in others of a bitter principle, of aro- 

 matic oil, and of coloring matter, all of which we may 

 find within the rind of an orange, so in the earth's 

 crust have been deposited, in different parts, granitic 

 veins, calcareous veins and quartz veins, each carrying 

 its own peculiar ores or other mineral species, the work 

 of successive and independent processes, often at widely 

 separated intervals of times. 



To attempt a detailed description of these various pro- 

 cesses would involve a. discussion of dynamical and chem- 

 ical principles requiring a volume, but I may call your 

 attention to some fundamental points which may indi- 

 cate the general nature of the problems presented, and 

 the mode of their solution. Of these, the first is the sol- 

 vent power of water. Of those bodies which are regarded 

 as insoluble, the greater part are soluble to a small 

 extent under ordinary conditions, and to a much greater 

 degree with increased temperature and pressure. Again, 

 very many such nearly insoluble bodies are found to as- 

 sume, under certain conditions, a soluble condition. 

 from which, however, they readily pass into one of com 

 parative insolubility. This two-fold character is ill us- 



