JANUARY 5, 1912] 
ete. In photometry a number of instru- 
ments have been developed or improved, 
including an automatie recording mechan- 
ism, a direct reading scale, a universal ro- 
tator, an improved integrating photometer, 
a direct recorder for life test work, an effi- 
ciency meter, ete. 
Many other examples of the kind may be 
cited. In every case, instrument makers 
and the public have the fullest access to 
all information concerning new instru- 
ments or improvements in old instruments. 
(e) Determining the Properties of Ma- 
terials—The fifth class of scientific investi- 
gations concerns the measurement of the 
properties of materials. Most of the work 
of this kind is included under the head of 
testing, the materials tested being in most 
cases samples of larger lots. But in some 
eases the work is done to find the average 
properties of a certain kind of material for 
the purpose of establishing a standard, or of 
finding how one property depends upon 
another. Examples of this kind are the in- 
vestigations on the mean resistivity and 
temperature coefficient of resistivity of 
commercial copper wire. Samples were 
obtained from many sources, both in 
America and Europe, and values obtained 
from measurements made by one of the 
largest manufacturers, whose instruments 
and standards had been verified by the 
bureau. 
In this way a mean value was obtained 
for commercial copper which was made the 
_ basis of a new wire table, computed by the 
bureau at the suggestion of the American 
Institute of Electrical Engineers, and 
which they at once adopted in place of 
their own table. These investigations also 
brought out a new relation between the 
temperature coefficient of resistivity and 
the resistivity itself, so that knowing 
either of these quantities, the other be- 
comes known. 
SCIENCE 13 
Another important investigation of this 
kind recently undertaken is on the rela- 
tion between the magnetic and mechanical 
properties of iron and steel, with a view 
of ascertaining whether it is practicable to 
test materials for mechanical flaws by 
magnetic methods. Many investigations 
on the properties of materials employed in 
electrical work are needed to answer the 
hundreds of questions constantly arising, 
and some of these will soon be undertaken 
in cooperation with one of the committees 
of the American Society for the Testing of 
Materials. 
3. ENGINEERING INVESTIGATIONS 
In addition to work of the character just 
described under the head of scientific in- 
vestigation, laboratory and field work have 
been conducted on several important prac- 
tical questions, which may be mentioned 
under the head of engineering investiga- 
tions. 
One of these had to do with the use of 
electricity in mines, and the work was 
undertaken for the purpose of formulating 
a set of rules suitable for enacting into 
law, or that could be utilized in revising 
existing laws, concerning the safe use of 
electricity for light, power and signals in 
mines. A careful study of coal mines 
using electricity, and of the regulations of 
European and other countries concerning 
the use of electricity in mines, was made, 
a great many mining engineers, mine in- 
spectors, mine superintendents and manu- 
facturers of mining machinery were con- 
sulted, and the results embodied in a pub- 
lication on the ‘‘Standardization of Elec- 
trical Practise in Mines.”’ 
Another investigation still in progress 
has to do with the state and municipal con- 
trol of the manufacture and sale of illumi- 
nating gas. The bureau has been making 
a thorough study of the methods of testing 
