FIELD WORK. 
By Marius R. Campbell. 
INTRODUCTION. 
The writer was assisted in the collection of coal for testing purposes 
throughout the field season by Mr. J. Shober Burrows and Mr. John 
W. Groves, and for a short time by Mr. Frank W. De Wolf. 
In a circular letter sent out early in the season the coal operators of 
the United States were invited to participate in these tests, upon the 
conditions stated in the act of Congress under which the work Avas 
carried on, namely, that all material to be tested should be delivered 
at the testing plant free of cost to the Government. It w r as decided 
by the committee in charge that for practical tests of the character 
contemplated not less than one carload of coal should be accepted. In 
response to this invitation offers of coal were made from almost every 
coal-producing State in the Union. From these offers it was decided 
to accept such samples as best represented the State from which they 
were obtained, and also the various fields or districts within the State. 
Owing, however, to the fact that the testing plant was put in opera- 
tion late in the season, it was found to be impossible to test all of the 
coal samples offered, and so a number of important coal fields and 
even States of large production are not represented. 
It is a generally recognized principle that the value of tests upon 
fuel and similar materials depends largely upon the wa} T in which the 
sample was obtained and what it represents. In the present work the 
committee in charge decided to give this feature special attention and 
in every ease possible to superintend the collection of the sample, so as 
to be in a position to guarantee that the coal tested fairly represented 
the coal produced from the mine as far as it is possible for one carload 
to represent the output of a mine. 
CAR SAMPLES. 
In actual operation the sampling was done as follows: 
After arrangements had been made for the coal, and its transporta- 
tion was assured, the representative of the testing plant visited the 
mine for the purpose of procuring a sample. He first entered the 
mine and carefully studied the character of the coal as shown in the 
18 
