96 
MEASUREMENT OF HIGH TEMPERATURES. 
[bull. 54 
die, the construction of which is as follows: A narrow but strong arch 
of brass, i i, carries two steel needles, n, which i>roject symmetrical^ 
into and through the brass tube Zc. It is obvious that the slip, on beinj. 
forced around the arch and needles, issues from the tube 1c as a biper 
forated tube, the dimensions of which, either as to external diameter o 
diameter of canals, depends solely on the thickness of the needles ant 
width of the tube h selected, and can therefore be varied at pleasure 
It is also obvious that the number of canals is immaterial so far as tin 
application of method is concerned. Fig. 17 (scale \) gives the die f o i 
making the tine porcelain tubing used in the crucibles, Fig. 13, above. 
Fig. 17. Die for porcelain tubes. Scale, {. 
When the slip is of proper consistency the tubes issue from the di< 
in a single length so long as the pressure of the plunger continues 
Tubes longer than a foot, however, break by their own weight if sue 
pended wet. Hence it is desirable to cut them off by a thin rectangula 
pine board of about 1 foot in length, held with its long edges near! 
vertical and its plane also slightly oblique to the vertical. A grea 
number of consecutive lengths of 1 foot may be laid side by side i; 
this way, like the bars of a gridiron, and then allowed to dry on th 
board before firing. Insulators of porcelain are smooth and compact 
but they become viscous and are even apt to fuse at higher temperatures 
Under these circumstances they not only stick to the central tubes c 
1 The brass arch, i i, to hold the pins w, was suggested to me by Doctor Halloed 
In my original apparatus the pins were fastened to the plunger. 
(750) 
