78 JOURNAL OF THE WASHINGTON ACADEMY OF SCIENCES VOL. 13, NO. 5 
The value of such a specification, however, is obviously dependent 
on two things which are very difficult to ensure. The first is the 
establishment of a temperature scale which is reliable and reproducible 
within 2 degrees or better at these high temperatures, and the second 
the construction of a furnace which approaches closely enough to 
uniform black body conditions to make sure that the part of the 
furnace from which light is emitted is really at the temperature 
assigned to it. 
Now these high temperature scales are based on and checked by 
melting points of pure metals. Years ago Waidner and Burgess 
suggested that Violle’s idea of using platinum at the melting point 
for a light standard might be made practicable if the platinum were 
not used as a free radiating surface, but merely served to control the 
temperature of a black body. Nearly everybody has recognized the 
essential soundness of this proposal, but for various reasons it has 
only recently been tried out experimentally. One of the obvious 
difficulties was the cost of the platinum which would be necessary if 
measurements were to be made on a black body radiator of anything 
like the ordinary kind. <A few years ago H. E. Ives conceived the 
idea of getting the desired effect with a moderate quantity of platinum 
by using for the black body a hollow platinum wedge electrically 
heated to the melting point. Observations were made on four wedges 
with very consistent results, the average brightness found being 
58.35 candles per square centimeter, with an extreme range of one-half 
per cent. Other data obtained in the same investigation were, how- 
ever, inconsistent, and extensive study would be required to determine 
the effect of a number of conditions which may affect the results. 
Although the wedge forms a satisfactory radiator for pyrometric 
work, there is serious doubt whether it can be satisfactory for the 
very exact approach to black body conditions required to give reliable 
candlepower values. 
Realizing the difficulties of proving that the wedge form conformed 
closely enough to complete black body conditions, Ives has more 
recently studied the possibilities of a hollow cylinder of platinum in 
which the conditions can be more definitely established. The results 
of this investigation were reported to the Franklin Institute a few 
weeks ago, but have not been published. 
The preliminary values reported show a highly satisfactory degree 
of consistency among the observations. Comparison of Ives’ results 
with those of Hyde, Forsythe, and Cady will be somewhat uncertain 
because it must depend on the temperature to be assigned as the 
