422 H. E. MERWIN CHEMICAL RESEARCHES ON SEDIMENTS 



perature of 10° centigrade, and as dolomite has been formed artificially 

 at somewhat elevated temperatures, it seems not an unpromising labora- 

 tory task to attempt — possibly by extrapolation of a series of quantitative 

 results at elevated temperatures — to answer some of the geologists' ques- 

 tions concerning dolomite. The fact that both dolomite and the common 

 forms of calcium carbonate usually crystallize well adds much to the hope 

 of getting definite results. 



OCEANIC RED CLAY 



The oceanic red clay has been considered to be nearly the end product 

 of the chemical action of sea-water on materials sinking through great 

 depths of the ocean and resting on the bottom. The sources and means 

 of distribution of parent materials have been discussed, the clays have 

 been analyzed chemically by different methods with different objects in 

 view, they have been studied microscopically — chiefly from the viewpoint 

 of the biologist— and certain well founded conclusions have been reached ; 

 yet it seems probable that when critical studies of the structures of the 

 complex granules of the clay have been made by means of the petrographic 

 microscope, after suitable chemical treatments, more silica of organic 

 origin and less decomposed pumice will be found than has hitherto been 

 supposed. The solubility relations of the elements most sparingly present 

 in sea-water and comparatively abundant in the red clay need much study, 

 and the chemical effects of the working over of constituents of the mud 

 in the alimentary tracts of animals should not be neglected. 



THE PRIMARY ROCK PHOSPHATES 



Geological relationships indicate that the extensive bedded phosphate 

 rocks were formed on sea floors either by direct deposition or by replace- 

 ment of oolitic or other limestones. Microscopical studies seem not to 

 have settled the question of replacement for any particular deposit; but 

 the more general chemical problems involved need not take this question 

 into consideration. 



, At present no formation of phosphate comparable in purity with older 

 deposits is known to be taking place. In fact, no source of phosphorus 

 adequate for such deposits under any probable method of concentration 

 is evident from the most recent water analyses, with the possible excep- 

 tion of water bodies in inclosed basins such as Lake Van, Armenia, which 

 covers many thousand square miles and may, like certain well known 

 lakes containing highly saline sulphate and carbonate waters, be rela- 

 tively rich in phosphorus. In ocean water phosphoric oxide is remark- 



