RUS.] 
PORCELAIN AIR THERMOMETRY. 
179 
clinical skill of the operator than to crucial errors of method. I hope 
an early day to produce a porcelain air thermometer made in one 
ece, glazed within and without, and provided with a tight-fitting cap- 
ary platinum stem. I also hope to make bulbs of fire clay, suitably 
azcd without, apparatus which will be available for the measurement 
temperature very much beyond the highest limit of the porcelain 
ermometer. The soldered air thermometer presupposes low-pressure 
easurements, such as this paper describes. 
Bulbs which are not perfectly tight may sometimes be closed by heat- 
g in a large furnace with glaze. I have used the one described below 
r this purpose. This process, however, is difficult and expensive, even 
low pressure is applied to suck the glaze into the capillary fissures and 
nals. It is best to endeavor to complete the soldering with the oxy- 
drogen flame, testing the quality of the joint with the air-pump after 
e bulb is again cold. 
It is well to insert a word here about gasometers. I used the simple 
-m of sheet zinc bell -jar G G G G (Fig. 35a), dipping in a reservoir of 
H. 
-A* 
Fig. 35a. Gasometers. Scale j\. 
ter, 1 1 m m. The bell-jar is provided with a guide, n n, and a conn- 
poise, K. The level of the water is shown at 1 1. Gasometers of this 
id are well known, and are furnished by Ritchie & Co., in Boston, 
purpose in this place is to indicate the great advantage gained by 
o stop-cocks, B, 0, for each jar, G G, G G; for in this way any number 
single jars may be coupled together. In Fig. 35a, for instance, the 
(833) 
