520 



EXPERIMENT STATION RECORD. 



fertilizer must be doubly increased to maintain the balance. How high a level 

 of production can be protitably maintained is determined by the prices that rule 

 for the crops, but there will always come a limit when the production can be no 

 longer increased by additions of fertilizer except at a loss; at such a stage it is 

 only the introduction of improved varieties or some variation in the methods of 

 cultivation inducing a better utilization of the fertilizer which will still profit- 

 ably increase the production per acre." 



The conservation and utilization of our natural resources, J. H. Pratt 

 (Jour. Elisha Mitchell Sci. Soc, 26 (J910), No. 1, pp. 1-25, pis. 12).— Thm article 

 describes the physiographic divisions of North Carolina and deals particularly 

 with the conservation and utilization of soils, forests, waterpowers, mineral 

 products, swamp lands, and fish industries. Methods of protecting soils from 

 erosion are described. 



A preliminary study of chemical denudation, F. W. Clarke (Stuithsn. Misc. 

 Collect., 56, No. 1935, pp. 19). — This article deals with the measurement of soil 

 denudation by means of the dissolved solids carried into the sea by rivers. 

 Denudation varies widely in different regions and watershetls. but an attempt 

 is made to estimate the mean denudation for different continents. The crude 

 estimates are as follows : 



Denudation values for each continent. 



From the figures reviewed it is estimated that 175,O40,(tO0 metric tons of 

 sodium are annually discharged into the sea. From this figure and the sodium 

 content of the ocean it is calculated that the probable age of the ocean is 

 S0,T26.0W years. 



[Second annual report of Florida State Geological Survey, 1909] {Fla. 

 Geol. Survey Ann. Rpt., 2 (1909), pp. 299, pis. 19, figs. 5, map i).— This con- 

 tains an Administrative Report, by E. H. Sellards; A Preliminary Report on 

 the Geology of Florida, by G. C. Matson and F. G. Clapp ; Topography and 

 Geology of Southern Florida, by S. Sanford; Mineral Industries, by E. H. 

 Sellards ; and The Fullers Earth Deposits of Gadsden County, with Notes on 

 Similar Deposits found Elsewhere in the State, by E. H. Sellards and H. 

 (iunter. The work reported was done in cooperation with the U. S. Geological 

 Survey and had special reference to the stratigraphy of the region. Among the 

 subjects of special agricultural interest which are dealt with are topography 

 and drainage, soils, and phosphate deposits. 



Bibliography of North Carolina geology, mineralogy and geography, with 

 a list of maps, F. B. Laney and Katharine H. Wood (N. C. Geol. and Econ. 

 Surrey Bui. 18, pp. 428). — It is stated that this " bibliography relating to North 

 Carolina geology, mineralogy, geography, and allied subjects, as paleontology, 

 meteorology, petrology, etc.. has been made just as complete as possible, al- 

 though there are undoubtedly certain references lieft out that should be included. 

 Over 200 periodicals have been examined, and in most cases complete files of 



