206 REPORTS OP INVESTIGATIONS AND PROJECTS. 



the case if the deformation is carried on more slowl}^ or at an increased tem- 

 perature. It has been foimd, furthermore, that if a column of Carrara 

 marble is deformed and is then allowed to remain undisturbed for several 

 months, its strength will increase with rest, but that a column deformed at 

 ordinary temperatures will not be increased in strength by a subsequent 

 process of annealing. 



In the case of dolomite it was found that while the strength of the rock 

 when deformed under differential pressure was increased if the temperature 

 during deformation was raised, and that while the rock after deformation re- 

 mained firm and coherent, the loss of strength upon deformation was in all 

 cases great. 



This experimental work is now practically completed and a full report, de- 

 scribing the methods employed and embodying the results obtained by the 

 study of a whole series of calcareous rocks, will be ready for publication 

 before the close of the present year. 



The second line of investigation to which reference has been made consists 

 of an experimental study of rocks under conditions found in the "zone of 

 flow." In these investigations Solenhofen limestone and Westerly granite 

 have been employed. The columns of these rocks, penetrated by fine holes 

 drilled through them in dififerent directions, have been inclosed in tightly fit- 

 ting tubes of nickel steel and submitted to compressive stresses of values cal- 

 culated to exist at different depths within the earth's crust, the conditions of 

 pressure in some experiments being those which according to hypothesis ob- 

 tain in the "zone of fracture" and others those in the "zone of flow." This 

 experimental work is not as yet in a sufficiently advanced state to enable gen- 

 eral conclusions to be reached, more especially as the effect of the factor of 

 temperature still remains to be studied. 



Becker, George F., U. S. Geological Survey, District of Columbia. Grant 

 No. 226. Bxperwients on elasticity and plasticity of solids. (For 

 previous reports see Year Books Nos. 3, 4, 5, and 6.) $7,500. 



Systematic observations on the elastic after-effect of steel tapes, to which 

 reference was made in the last report, were resumed during the latter part of 

 December, and are being continued with satisfactory results. As was men- 

 tioned last year, the temperature is controlled by means of an electric furnace 

 operated in connection with an electric thermostat, and the measurements are 

 made with a specially constructed interferometer. The design and construc- 

 tion of this interferometer has been a most difficult problem. The apparatus 

 in its present form is quite satisfactory, but it is expected that improvements 

 will be made as the work proceeds. The time interval during which the ma- 

 terial is strained, or is allowed to recover from strain, ranges from 4 to 10 

 weeks, depending upon the magnitude of the strain. A second line of inves- 



