338 
scientific investigations, published by those 
societies during the year ending June 1, 
1897, was received. 
One of the most important functions of 
the Association is represented by the work 
of its committees. In addition to the three 
reports to the Council many very valuable 
reports were presented at Toronto before 
the sections, which will be noticed in 
special articles on the work of the sections 
to be published in subsequent issues of 
SCIENCE. 
THE AMERICAN ASSOCIATION FOR THE AD- 
VANCEMENT OF SCIENCE. 
LONG RANGE TEMPERATURE AND PRESSURE 
VARIABLES IN PHYSICS.* 
METHODS OF PYROMETRY. 
THE endeavor to provide suitable appara- 
tus for high temperature measurement is 
one of long standing. The student of the 
subject is fairly overwhelmed with the 
variety of devices which have been proposed. 
There are few phenomena in physics which 
have not in some way or other been im- 
pressed into pyrometric service, often in- 
deed by methods of exquisite physical tor- 
ture. I cannot, of course, even advert to 
many of these this afternoon, as my pur- 
pose will have to be restricted to such de- 
vices as have usefully survived. Thus a 
whole group of ‘ intrinsic thermoscopes,’ as 
Lord Kelvin calls them—apparatus in 
which some property of the substance is 
singled out for measurement—will be over- 
looked. Pyrometry will some day receive 
substantial aid from the phenomena of solid 
thermal expansion, dear to the hearts of 
old Wedgewood, of Professor Daniells, of 
the citoyen Guyton-Morveau, and recently 
to Professors Nichols, Joly and others ; but 
even the ‘meldometer,’ which has received 
Ramsay’s encouragement and recent heroic 
attempts to measure the expansion of plati- 
* Address by Professor Carl Barus, Vice-President 
and Chairman of Section B (Physics). 
SCIENCE. 
[N. 8. Vo. VI. No. 140. 
num, have not yet entered the arena to 
stay.* The same may be said of vapor 
pressure, ebullition and certain dissocia- 
tions, of which the former is entirely too 
liberal in dispensing pressure, and the lat- 
ter too negligent in readjusting it. Little 
has been done with heat conduction re- 
garded as subservient to the measurement 
of high temperatures ; little with color and 
the spectrum, even though Draper and 
Langley in this country and many others 
abroad have paid tribute ; little with polari- 
zation. The wave-length of sound has told 
Cagniard Latour and our own A. M. Mayer 
much about high temperature, but it did not 
tell them enough. 
Throughout the history of pyrometry, 
fusion seems to have come forward for jour- 
neyman duty. What is more convenient 
than to find whether the degree of red heat 
is too low or too high from the fusion of 
prepared alloys. As far back as 1828 Prin- 
sep, aware of the golden opportunity, with 
his golden air thermometer determined the 
melting point of some equally precious al- 
loys of gold, silver and platinum, and de- 
termined them very well. Other alloys 
were atterwards substituted and graded 
mixtures made of quartz, chalk, kaolin and 
feldspar for the purpose. Efforts to obtain 
more accurate values are due to Becquerel ; 
but the absolute values most widely used 
until quite recently, namely, the melting 
points of silver (958°), gold (1035°), cop- 
per (1054°), palladium (1500°), platinum 
(1775°), iridium (1950°), are due to the re- 
searches of Violle. 
Interest in high temperature fusions has 
of recent date rather increased than abated. 
The demand for more accurate data has 
been met by the Reichsanstalt, and we have 
now a set of values for silver, copper, gold, 
nickel, palladium and platinum in terms of 
* Noteworthy attempts to replace mercury by a 
liquid potassio-sodium alloy in glass thermometers 
are among the novelties. 
