Geology and Mineralogy. 69 



1 1 . Joseph Henry and the Magnetic Telegraph : An address deliv- 

 ered at Princeton College, June 16, 1885, by Edward N. Dicker- 

 son, LL.D. 66 pp. Svo. New York, 1885. (C. Scribner's Sons.) — 

 A just tribute to the late Professor Henry, reviewing bis scientific 

 labors and discoveries, and giving them their right place in the 

 progress of physical science. The historian of the world's 

 science should consult it for the review of the facts which it 

 presents. 



12. '•'■The Force Function in Crystals /" by Alfred Einhorn", 

 Ph.D. Communicated to the Royal Society, Nov. 27, 1884. 

 (Proceedings of the Royal Society, vol. xxxviii, No. 235.) — The 

 first part of the paper, which appears at present, restricts itself to 

 the consideration of the Tesseral, Tetragonal and Rhombic sys- 

 tems. By means of a well founded assumption in regard to the 

 stress distribution in crystals of the above systems, the equilib- 

 rium conditions are deduced which further involve that the 

 boundary of the configuration must either be plane or spherical. 

 It also appears that the statical conditions of the agency which 

 causes crystallization are the same as those so well investigated 

 for gravitation and electricity. 



The paper is divided into three chapters. The first chapter 

 treats of the " Foundation of the Assumption." The assumption 

 is, that the stress upon any particle can only be transmitted in 

 six directions-lines, respectively at right angles in pairs to the 

 three crystallographic axes — it is a consequence of the internal 

 structure which is shown to be analogous to that of an ordinary 

 cannon-ball pile by means of the cleavage properties, the external 

 form and inertia relations of crystals. 



The second chapter, " Derivation of the Force Function," ap- 

 plies the three general differential equilibrium equations of an 

 elastic solid subject to internal forces to the stated stress distri- 

 bution. In order to effect this it was necessary to deduce some 

 peculiarities of the force function in a system of uniform density 

 in equilibrium and subject to internal forces when referred to the 

 three principal axes of inertia through the mass center. The 

 character of the attracting agency here becomes evident. 



The third heading is " Determination of the Boundary." Under 

 this heading the nature of the boundary is determined and is 

 shown to be either plane or spherical. And by the application of 

 Green's theorem if also becomes clear that inasmuch as the stati- 

 cal conditions of the crystallizing agent are now understood ; the 

 force functions derived in the preceding chapter can be inde- 

 pendently deduced without aid of the assumption from any one 

 of the primitive forms of the systems under consideration, o. n. r. 



II. Geology and Mlnebalog-y. 



1. The Missouri Coteau and its Moraines. — Professor J. E. 

 Todd gives an account, in the Proc. Amer. Assoc, xxxiii, 381, 1884, 

 of the features and drift deposits of the Coteau and illustrates 



