Apeil 20, 1900.] 



SCIENCK 



631 



of the country. Human figures, horses, wea- 

 pons, birds and symbols are the most common 

 forms represented. In one place a man is seen 

 leading seven ponies. Again the gigantic fig- 

 ure of a man about fifteen feet in length is re- 

 clining. Spears, shields, eagles, turtles, men on 

 foot and horseback are scattered over the surface 

 of the rocks in apparently endless confusion. 



The soft sandstone is rapidly weathering 

 away. In many places only mere outlines of 

 the figures remain. Often the entire face of the 

 cliff will fall off. It is but a question of a few 

 years when the last trace of the figures will be 

 gone. But more destructive than the ravages 

 of time is the vandalism of man. It would seem 

 that every white man who has visited these 

 localities has felt it incumbent upon him to 

 scratch his own name on the rock. Thisof itself 

 might be considered only an exhibition of poor 

 taste, were it not for the fact that he has almost 

 invariably chosen to carve his own plebeian 

 name over a pictograph. And with characteris- 

 tic American thoroughness the scrawling letters 

 are so broad and deep that the older 

 figure is usually obliterated. Thus it is that 

 many of the best examples of Indian picture 

 writing have been and are being destroyed. 

 Unfortunately there seems to be no way to 

 prevent this vandalism. In a few years these 

 records of a forgotten people shall have disap- 

 peared. Charles Newton Gould. 



University of Nebraska, 

 February 10, 1900. 



SYSTEMATIC AREANGTSMENT OF ORE DEPOSITS 

 ON A GEOLOGICAL BASIS. 



There has been, of late years, a growing 

 tendency to consider ore deposits from a geolog- 

 ical standpoint. Heretofore it has been the 

 general custom to almost ignore the physical 

 character and structure of the rock formations 

 with which given ore bodies are associated. 



As some sort of comparison must be neces- 

 sarily made between ore bodies as they are de- 

 veloped, their classification crude though it is, 

 begins to take place early in their consideration. 

 With the ordinary miner such a scheme is 

 strictly empirical, according to some obvious 

 features presented. From this to a scientific 

 plan the step is a long one. 



Why the classification of ore bodies has re- 

 mained so long in an unsatisfactory state, and 

 little or no real progress made, while other re- 

 lated branches of knowledge have advanced 

 with gigantic strides, finds its chief explanation 

 in the fact that our methods of investigating 

 the phenomena connected with the alteration 

 of rocks generally were inadequate. Until the 

 beginning of the last quarter of our century 

 these methods were advanced but little beyond 

 what they were a hundred years before. The 

 activity in natural science studies was in other 

 directions. 



With the application of the microscope to the 

 rocks and the openingof a new world to the geol- 

 ogist as vast and as interesting as that which the 

 same magnifying glass gave to the biologist, 

 rock metamorphism assumed a new role. Ore 

 formation is found to be merely a special phase 

 of general rock alteration. It goes ou under 

 the same conditions and by the workings of the 

 same geological processes. 



The study of ore genesis and relationships of 

 ore bodies has become a strictly geological 

 proposition. The recent investigation of the 

 ores from the standpoint of geology appears to 

 be capable of producing good results. It is re- 

 plete with suggestive inference. With modern 

 geology as a foundation the near future cannot 

 but open up to us unheard of and unthought of 

 advantages in the practical development of the 

 ores. We stand on the threshold of a new era. 



On this topic we get a glimpse of the general 

 trend of modern thought respecting the genesis 

 of ore deposits by reference to the principles, 

 formulated by Prof. C. R. Van Hise in his 

 treatise on the general metamorphism of rocks 

 (not yet published), as adapted recently to ore 

 deposits. This summary is contained in his paper 

 on ' Some Principles controlling the Deposition 

 of Ores,' read at the Washington meeting of the 

 American Institute of Mining Engineers. 



So far as the classification of ore deposits is 

 concerned we appear safe in concluding that : 



(1) The chief feature wherein the classifica- 

 tory scheme hereafter presented differs from 

 others, is in the prominence given to geological 

 occurrence and the direct operation of the 

 geological processes as essential factors in the 

 genesis of the ore bodies. 



