PREFACE. 
The present publication is the first contribution to a research on 
the physical constants of rocks, the experiments of which are to follow 
a general plan devised by Mr. Clarence King, former Director of the 
U. S. Geological Survey. Retaining such questions as have an imme- 
diate bearing on dynamical geology for his own investigation, Mr. King 
honored me by placing the purely physical part of the inquiry into my 
hands. Our undertaking was begun some years ago. I was in com- 
munication with Mr. King as far back as the summer 1 of 1881, and 
much work in the way of determining the possibilities of the problems, 
of organizing methods of research, and of selecting and devising suit- 
able apparatus, was done prior to 1882. 
Not, however, until January of 1882 were definite steps taken toward 
the organization of a physical laboratory. The work in view was of 
too elaborate a nature to be undertaken by a single observer; and at 
my request Mr. King invited Dr. Vincent Strouhal, then of the Univer- 
sity of Wiirzburg, ro share my labors. Our early endeavors were of a 
pioneering kind. With the exception of a few instruments which bad 
been used in the physical work in Nevada, and which came into our 
possession through the kindness of Mr. G. F. Becker, the early labora- 
tory of the Survey was furnished entirely at the expense of Mr. King. 
It is but just, in this place, to acknowledge a debt of gratitude which 
I in particular owe to Mr. Becker, by whom our efforts in the direction 
of physical research were befriended and advanced. It will be remem- 
bered that the first physical work on the Geological Survey was done 
under his direct supervision. 2 
The general scope of the problems to be undertaken, so far at least 
as their purely physical relations are concerned, has been briefly given 
in an article prepared under the direction of Mr. King, and printed by 
the Survey 3 for the year ending June 30, 1882. In this article I classi- 
fied the parts of the proposed research as follows: 
(a) Phenomena of fusiou. These would comprehend temperature of fusion, specific 
volume at this temperature of the solid and of the liquid materials respect- 
ively, heat expansion, compressibility, latent heat of fusion, specific 
heats — all considered with especial reference to their variation with press- 
ure. 
1 Cf. Second Ann. Rept. U. S. Geol. Survey, 1882, p. 40. 
2 Cf. First Ann. Rept. IT. S. Geol. Survey, 1880, p. 4(5; Second Ann. Rept. U. S. Geol. 
Survey, 1882, pp. 311, 319-330. 
■ J Third Ann. Rept. U. S. Geol. Survey, 1883, pp. 3-9. 
Bull. 54 2 (671) I 7 
