BARUS.] 
PORCELAIN AIR THERMOMETRY. 
171 
Table 41. — Dimensions of copper cap War g tubes. 
No. 
Weight. 
Length. 
Thick- 
ness. 
Caliber. 
Volume 
per cm. 
0- 
em. 
cm. 
cm. 
cc. 
1 
5.81 
81. 5 
0.119 
0.063 
0. 0031 
2 
5.39 
95. 
0. 103 
0.050 
0. 0020 
3 
10.81 
144. 
0. 123 
0.066 
0. 0034 
4 
4.74 
67.6 
0. 119 
0.064 
0. 0032 
5 
7.34 
105.6 
0.118 
0.062 
0. 0031 
6 
7.07 
108. 2 
0.119 
0.069 
0. 0037 
7 
2.99 
101.7 
0.077 
0.041 
0. 0013 
Among these No. 7, a very perfect tube, is most remarkable. The 
tubes were made in February, 1884. 
Since that time I was fortunate in inducing the Malvern Platinum 
Works to undertake the manufacture of such tubing in silver and plati- 
num. With the latter metal they succeeded well, and the dimensions 
of samples of the (platinum) tubing made for me are given in Table 42. 
Table 42. — Dimensions of platinum capillary tubing. 
No. 
Weight. 
Length. 
Thick- 
ness. 
Caliber. 
Volume 
per cm. 
9- 
cm. 
cm. 
cm. 
cc. 
1 
9.02 
51. 
0.115 
0. 0524 
0. 00215 
2 
7.25 
42.6 
0.115 
560 
246 
3 
7.07 
41. 5 
0.115 
561 
247 
4 
7.62 
44.4 
0.115 
553 
240 
These tubes may be obtained in any length not exceeding 5 meters. It 
is usually sufficient to use meter lengths only, cleaning each thoroughly 
with naphtha, alkalies, and acids; passing capillary iron wire quite 
through the tube, drying, and then heating to redness before inserting. 
The use of capillary tubes presupposes slow rise and fall of temperature 
during calibration. To this end my furnaces have been constructed, 
rhe data of Tables 41 and 42 will appear more striking when placed in 
contrast with the capacities of the bulb and stem of the porcelain gas 
:hermometer. These are 300 cc and 0.012 cc per centimeter, respectively. 
Kundt has successfully used capillary glass tubes drawn out so thin 
is to be filamentary. 
Platinum capillary tubes (the present being the first ever made, I 
jelieve) are an especially useful apparatus and subserve many ulterior 
purposes. They are used, in chap. V, for instance, as an essential part of 
ftie transpiration. thermometer, and to investigate the laws of transpira- 
:ion and gas viscosity at high temperatures. 
Porcelain gas-thermometer bulbs. — Various forms of gas-thermometer 
3ulbs, as given in Figs. 31, 32, and 33, drawn to a scale of J, were used. 
(825) 
