ERRATA 



To article on Schisiosity a>id Slaty Cleavage. — Owing to absence from 

 the United States, Mr. Becker had no opportunity of correcting proof 

 of this paper and the following errors crept into the symbolic 

 expressions : 



The first sentences and the footnote on page 431 should read as 

 follows: "If horizontal edges of the unit cube are extended in the 

 ratio a, so that these edges in the strained mass have a length a, then 



the vertical edsres are contracted in the ratio -. It is usual to define 

 '^ a 



the quantity a as the ' amount ' of shear. If the unstrained cube 



a 



contained a sphere, this in the strained mass would become an ellipsoid 



I * 

 with axes a, i, — • 



" Since a is greater than unity, and - less, .... 



* " If the equation of the sphere is x^ + j/^ + 2^ ^ i, and if x^, y-^ , Zi are the values 



which the same points have after strain, Xi = a x ; yi = - and Zi =z. Substituting in 



the equation of the sphere evidently + a^ y-? + Zj^ =r i represents the sphere after 



deformation. The volume of the ellipsoid is - :r. -. a. i = — , which is also the vol- 



3 a 3 



ume of the sphere." ^ ^ 



On page 432, footnote, for "undisturbed" read " undistorted." 



On page 439 the sentence beginning on the eighth line should 

 read thus : " If x, y, z are the initial coordinates, x^ , y^ , z^ the final 

 coordinates of a point, and d a constant, x =^ x^; y =^y^; z^ z^—y^b 

 represents a scission." 



On page 441, footnote, for " - /3 " read " — ^." 



On page 444, line 14, for " more " read " mere." 



To article on Laccolites i?i Southeastern Colorado. — On page 818, 

 fourth line from bottom, for "formation " read " deformation." 



6" 



