&i>s.] PORCELAIN AIR THERMOMETRY. 177 
Having given the arrangement of the rotational apparatus, I have 
> add a description of the sliding oxy hydrogen blow-pipe. The blow- 
ipe itself is shown at cd, and the plan contains dotted lines showing 
le construction of the interior. Hydrogen from the gasometers enters 
rrough a large tubulure, o, fully 0.5"" in diameter, compressed oxygen 
irough a finer tubulure, d, the jet end of which is not quite 0.08 cm in 
iameter. This blow-pipe burns quietly, and if well constructed the 
ame is visibly one foot in length, tapering with perfect regularity from 
le large diameter 0.5 cm to a point. The attachment of this blow- 
pe to the frame-work which carries it is such that in its horizontal 
osition the flame plays through the lateral hole of the lime furnace, 
ripinging upon the neck of the bulb to be soldered. The collar w, into 
hich the blow-pipe is fastened by the screw e, has a lateral axis or 
vivel, in virtue of which the blow-pipe may be rotated around an axis 
erpendicular to itself (a kind of trunnion), and clamped at any given 
jgle by the screw h. In this way the flame may be made to impinge 
gainst any part of the stem or neck of the bulb to be soldered, at 
Measure. The sliding arrangement into which the swivel is clamped 
msists of two parts, the slide proper, #, moving freely along the rod 
5 and the part m, which is practically a nut of the male screw g h. The 
irts q and m can be joined at pleasure by aid of the steel pin s s and 
^responding clamp screw. If the latter be loosened the blow-pipe may 
> made to approach the air thermometer as near as desirable. The 
rew g h ends in a wheel, i i, rotated by a belt, which passes over the 
wer spindle of the pulley-wheel A B. An axle, Jc ft, carries two inde- 
mdeut rollers, by which the direction of the belt is changed. In this 
ay the screw is kept in motion to correspond with the rotation of the 
r-thermometer bulb. 
When the flame is lit and the soldering commenced, the blow-pipe car- 
ige is placed as near as practicable to the end h of the screw. As the 
tation continues the flame gradually approaches the air thermometer, 
id the heat is therefore intensified with perfect regularity. Inasmuch as 
e flame impinges on the neck while in a state of rotation, it is quite 
>vious that the liability to fracture or breakage is by this device di- 
inished to a minimum. I add that to prevent interferences the 
read at the end of the screw g h has been cut away, so that when the 
it m is near these end points there may be no further tendency to 
[>ve. An intermediate rod, r r, and a sliding piece, e t, increases the 
sadiness of motion. The carriage as a whole is supported by two up- 
hts, JVand Z Z. 
The feldspar to be used for .soldering is to be ground most carefully 
an impalpable powder and mixed with mucilage or water to a plastic 
pasty consistency. This is spread uniformly around the neck of the 
lb, so as to form a ring where the edge of the neck shoulders against 
e stem. It is then allowed to dry. Stem and neck should fit snugly 
>m the outset ; at least all waste space should be calked with feldspar. 
Bull. 54 12 (831) 
