VITAL CONCENTRATION 27 



corals, crinoids, mollusks, etcetera, as is well known, form terranes which 

 in the aggregate measure thousands of cubic miles. The geological and 

 iadustrial importance of these organic accumulations and the clearness 

 with which they demonstrate the continuous action of life in segregat- 

 ing mineral matter throughout the zoic division of geological time speak 

 eloquently in favor of the definite recognition of the principle of concen- 

 tration as a geological process. 



SILICA 



What has been said relative to the concentration of calcium car- 

 bonate might be said again concerning silica, with but little change in 

 the wording. The diatoms among plants and radiolaria and sponges, 

 especially among animals, have throughout eons of time been forming 

 stones for the geological temple, and through the solution and reconcen- 

 tration of the material secreted have furnished a cement for other stones 

 in the structure. 



The importance of the principle of concentration concerning the result- 

 ant or by-products of the vital functions of plants and animals might 

 be illustrated at greater length, and the conditions leading to the accu- 

 mulation of deposits of iron, phosphorus, sulphur, and many other sub^ 

 stances, dwelt upon, but enough has perhaps been said to show the impor- 

 tance of the subject. 



Summary 



Attention has been invited to the broader phases of the processes active 

 in nature which lead to the concentration of mineral matter. A classi- 

 fication of the processes referred to has been suggested, the primary 

 divisions of which take cognizance of the dominant form of energy, 

 whether mechanical, chemical, physical-chemical, or vital, which in cer- 

 tain large groups of the changes considered exert the major control. Sub- 

 divisions of these primary classes, based on determining or qualifying 

 conditions and on selective or transposing agencies, have also been intro- 

 duced, as it is thought they will be of service to the geologist. The 

 scheme is intended to be sufficiently elastic to admit of the interpola- 

 tion of as yet unrecognized determining or qualifying conditions or 

 agencies and of a minute classification of products or results. 



As an attempt has been made to show, the field of operation of the 

 principles presented is as extensive as the earth, and embraces not only 

 its surface, but its interior, and is as far reaching as geological time. 

 Although an underlying principle has been dwelt upon and emphasized, 



