336 Journal of Agricultural Research voI.x.no. 7 



The Mesaverde contained much colored sandstone and the coal deposit 

 of the period. The sandstone shows much cross-bedding, marks, etc., 

 indicating shallow water deposits. 



The sea partially disappeared at the end of the Mesaverde, so the 

 Tertiary strata lies unconformably on it over large areas. The climate 

 of the Tertiary was similar to the Upper Cretaceous, and much of the 

 material deposited in the Tertiary seas was derived from the weathered 

 Cretaceous. The salts in the shallow seas seem to have their origin in 

 the concentrating of sea waters encroaching on the land. 



It is out of this material, heavily impregnated with the alkali salts, that 

 many of the soils of the arid West are formed. The climate continued 

 to be arid, and the salts deposited with the shale and sandstone in a 

 widely disseminated form have been protected from leaching not only 

 by the limited rainfall of the area but also by the impervious covering of 

 plastic clay resulting from the weathering of the shale. 



METHOD OF ANALYSIS 



The ground-up rock or soil was extracted with pure distilled water in 

 the ratio of i part of fine-ground rock to 20 parts of water. Usuallly 

 whenever the quantity of rock would permit, 100 gm. of the rock material 

 was treated with 2,000 c. c. of water for eight hours in a shaking machine. 

 The extract was then filtered through a Chamberland-Pasteur filter by 

 means of compressed air. 



The soil extract was analyzed for total salts, calcium, magnesium, 

 carbonic acid, sulphuric acid, chlorin, potassium, and nitric nitrogen. 

 The methods of analysis, except for nitric nitrogen, were essentially those 

 of the Association of Official Agricultural Chemists^ for alkali waters. 

 Owing to the high content of chlorin, the aluminium reduction method as 

 proposed by Moore (7) was used for the determination of nitrates as fol- 

 lows : 200 c. c. of the soil extract were boiled down to small volume to expel 

 all free ammonia. The solution was then transferred to 1 25 c. c. test tubes, 

 and 2 c. c. of strong sodium hydroxid and about i gm. of aluminium foil 

 added. The tube was then fitted with one-hole rubber stopper contain- 

 ing a tube drawn out to a capillary. The reduction was allowed to 

 go on at about 21° to 22° C. for about 12 hours. The solution was then 

 transferred to a 500-c. c. Kjeldahl flask, 150 c. c. of ammonia.free water 

 added, the ammonia distilled into standard sulphuric acid (N/jo), and 

 the excess titrated against standard alkali (N/jo), using lacmoid as an 

 indicator. 



SOLUBLE SALTS IN CRETACEOUS SANDSTONE 



Twelve samples of Cretaceous sandstone were collected and analyzed 

 for water-soluble salts; the results are recorded in Table I as pounds per 

 2,000,000 of sandstone. The results are arranged in the table in the prder 

 of the highest nitric-nitrogen content. 



1 Wiley, H.W.,ed. Extracts from the proceedings of the association of official agricui<- 

 TURAL chemists, 1909. U. S. Dept. Agr. Bur. Chem. Circ. 52, 33 p. 1910. 



