0. T. Sherman—Residual Elasticity, ete., of Glass. 385 
ee ha A notes of the relation observed by Dr. Weber 
between the residual elasticity and the chemical constitution of 
glass ; by O. T. SHmRMAN. 
make the temperature record independent of the condition or 
Past history of the thermometer has proved a rather complex 
Problem. ‘The earliest attempts, regarding the depression 
Tegular, adopted as the fundamental distance the interval 
between the freezing and boiling points obtained after a long 
test, and for the false position of the zero, applied a correction 
Proportional to the first power of the temperature. In 1880 it 
is Shown that better results were obtained by considering 
= interval between the fixed points obtained directly after 
heating as the fundamental length, and calculating the position 
of the zero by a formula depending upon the second power 
of the temperature. A third method determines the errors of 
the instrament directly after it has been heated to the boiling 
this cause the Normal-Archungs-Commission has for some 
me past been analytically and synthetically examining the 
Onstitution of the glass which gave the least depression. In 
Volume xxxvi of the “ Sitzungsberichte der Kéniglich Preuss- 
ischen Academie der Wissenschaften zu Berlin,” Dr. Weber 
“Ss recently stated as the first result of their work: that glass 
has the least depression in which the ratio of soda to potash 
°r potash to soda is the least. Ina previous number of the 
“ame publication, Dr. Weber has given twenty-three analyses 
of the glass together with the observed depression. It is a mat- 
‘er of interest to discuss these with regard to the same point. 
In the following curve we have represented the records of 
th articles. The ordinates represent depressions in tenths of 
4 degree centigrade, the abscissx, the ratio of potas 
. It will be seen that while the greater portion of the observa- 
Hons may be represented by a smooth curve yet six or at least 
