116 G. F. Becker — Im/paot Friction and Faulting. 



thermometers of this kind can be constructed for a few degrees 

 of range with which, by comparatively rude processes the 

 measurements may be correct within a very small fraction of a 

 degree. For use in earth temperature measurements, the ther- 

 mometer will be inclosed in a strong brass tube for protection 

 and the connection with the point of observation made by 

 means of a cable of heav}^ copper wire. The cable will of 

 course form a part of R in equation (2), but as it is a con- 

 stant, the substitution of one cable for another, if necessary, 

 will affect the position and not the form of the calibration curve. 

 Its resistance must be small, relatively, and the influence of 

 temperature upon it may be neglected. 



With this device a temperature observation may be taken in 

 less than a minute, no time being consumed in the preparation 

 of liquids of known temperature at the observing station as in 

 the use of the thermo-j unction or the resistance coil. 



Art. XVII. — Impact Friction and Faulting ; by George F. 



Becker. 



Bearing of the subject. — Some time since I submitted certain 

 phenomena of faulting to analysis and endeavored to show how 

 it might happen that a movement in the earth's crust, instead 

 of being confined to a single surface, would be distributed 

 over a great number of substantially parallel surfaces.* That 

 such occurrences are frequent is certain. They are called step 

 faults by Mr. Greikief and are stated to be common in the coal 

 fields bordering on the Forth. Professor Heim has also called 

 attention to similar instances.:}: The parallel systems of veins 

 found in a large proportion of mining districts, and even some 

 forms of complex lodes, involve such a division of the country. 

 Landslides frequently show a separation of the moving soil 

 into extraordinarily regular sheets a foot or two in thickness, 

 indeed during the spring of the past year I examined scores 

 of such slides in the Coast Ranges of California, some of them 

 covering forty or fifty acres in extent. Finally some mono- 

 clinal faults may probably be considered as step faults where 

 the intervening masses are not too broad to permit of their dis- 

 playing independent rigidity and, for these instances at least, 

 the relations between monoclinal and anticlinal faults may be 

 elucidated. It is clear that the subject is one of more than 

 merely local importance and deserving of the attention both of 



* The Geology of the Comstock Lode (Monograph U. S. Geol. Survey, vol. iii), 

 p. 156. 



f Test-book of Geology, p. 532. \ Mechanismus der Gebirgsbildung. 



