546 ISRAEL C. RUSSELL 



deposits like the oozes on the sea-floor, beds of diatomaceous earth, 

 deposits about hot springs, the so-called marl of fresh- water lakes, 

 etc. A review of the several ways in which such accumulations are 

 formed, and an extension of the search in various directions, give 

 promise that other and equally wonderful results flowing from the 

 activities of the lowest form of life would be discovered. The mode 

 of deposition of iron, and perhaps of manganese, the generation of 

 hydrocarbons, the origin of extensive sheets of seemingly non-fossil- 

 iferous limestone and dolomite, the method by which the beautiful 

 onyx marbles are laid down, film on film, the nature of the chert so 

 abundant in many terranes and so conspicuous in the surface waste of 

 extensive regions, and other equally important deposits which exert 

 a profound and frequently controlhng influence on topographic forms, 

 seemingly demand study with the hypothesis in mind that they owe 

 their origin to the vital action of low forms of plants or animals. 

 Not only the concentration of mineral matter by one-celled organisms, 

 but the part played by similar organisms in the comprehensive pro- 

 cesses of denudation, also invites renewed attention. Many of the 

 organisms in question do not secrete hard parts, and hence are 

 incapable of directly aiding in the concentration of inorganic sohds 

 on the surface of the lithosphere. If not assisting in the building of 

 physiographic structures, the suspicion is warrantable that they are 

 engaged in sapping their foundations. The wide distribution of one- 

 celled organisms — and indeed, as one may say, their omnipresence 

 on the earth's surface — and their seeming independence, as a class, 

 to diiTerences in temperature, light, and humidity, enable them to 

 exert an unseen and silent influence, not suspected until some cumu- 

 lative and conspicuous result is reached. The importance of bac- 

 teria in promoting decay, and in consequence the formation of acids 

 which take a leading part in the solution and redeposition of mineral 

 substances, the role played by certain legions of the invisible hosts in 

 secreting nitrogen from the air and thus aiding vegetable growth 

 and perhaps to be held accountable also for the concentration of 

 nitrates in cavern earths, the part others play in fermentation, and 

 the diseases produced in plants and animals by both bacteria and 

 protozoa, render it evident that an energy of primary importance to 

 the physiographer is furnished by these the lowest of living forms. 



