BARL6] PREFACE. 19 
partment of Yale College for uiany favors which they kindly extended 
to us. 
The researches made in New Haven, in so far as they fall within the 
scope of the present volume, are recorded in Chapter I. The bulk of 
our New Haven work, however, was in organizing a working laboratory 
and determining the errors and the constants of the instruments, and 
solving other problems which do not command sufficient general inter- 
est to be chronicled. The high- temperature work prosecuted there was 
laid out on a large scale, and the practical management of it is largely 
due to Dr. Hallock. Following Deville and Troost, the plan was one in 
which large masses of substances are thermally operated upon. Un- 
doubtedly these researches would have led to important results beyond 
those of Chapter I if there had been time to carry them consistently 
through to the end. 
The work in New Haven was not satisfactorily completed. In July, 
1883, with the appointment of Prof. F. W. Clarke as chief chemist of 
the Geological Survey, our laboratory became officially counected with 
the chemical laboratory. Conformably with the further decision of the 
Director, by which the divers laboratories of the Geological Survey 
were united in one central laboratory in Washington, it was again neces- 
sary to change our basis of operations, this time (in November, 1884) from 
New Haven to Washington. In the quarters assigned to us in the U. S. 
National Museum, temperature work on so large a scale as the New 
Haven work appeared impracticable, and it was therefore abandoned. 
In the mean time Dr. Hallock had been placed in charge of a series 
of independent researches not connected with ray work, and the experi- 
ments in hand were carried forward by myself to the point indicated 
in the present volume. Of course I owe much to the experience gained 
in our mutual efforts, detailed in Chapter I. 
In the introductory pages I give a succinct account of the chief 
methods of pyroinetry which have thus far been put to the test. 
I was fortunate in being able to avail myself of the fine working 
library of the American Academy, and I owe much to the courtesy of 
Dr. Austin Holden, the librarian in charge. 
The actual investigations, as contained in Chapters II, III, IV, and 
V, were adapted to the conditions prevailing at the National Museum. 
In place of the dangerous and cumbersome apparatus of the former 
laboratory, the endeavor is made to reduce all apparatus to the small- 
est dimensions compatible with reasonable accuracy of measurement. 
Methods of calibration of this kind based upon known thermal data 
(boiling points) are developed in Chapter II. 
I make in Chapter III a cursory survey of certain pyro-electric proper- 
ties of the alloys of platinum. Curiously enough, the data of this chapter 
led to a striking result, inasmuch as it appears that the zero resistance 
/(0), if the resistance at t° be r=f(t) ), and the zero temperature coeffi- 
cient /'(0)//(0), are related to each other by a law which during the 
(673) 
