390 Messrs. Holborn and Austin on Disintegration of 
without irregularities. The different strips could not there- 
fore be pro operly compared with one another, but this was 
not of great moment as the chief object 
of the work was the comparison of the 
disintegration of the same strip under 
different conditions. 
The 75 mm. long strips were clamped 
to 6 mm. thick copper wires and the 
whole introduced into a glass tube 
(fic. 1) 12 cm. in diameter, by means 
of a ground-glass connexion. The 
copper wires were cemented into the 
glass with sealing-wax. All the other 
external connexions of the tube were 
rendered tight with mercury. The 
tube was also provided with a side tube 
containing P,O; to be used at low gas 
pressures. The current was introduced 
through mercury cups in which the 
ends of the copper wires rested. 
The metal strips were too narrow for 
direct comparison with the optical 
pyrometer, therefore a 3 mm. wide, electrically heated plati- 
num band was brought to the required temperature. Against 
this the metal strip in the tube was projected, and heated 
until it attained the same degree of brightness. 
Contrary to the observations on the broad metal strips, a 
diminution of the disintegration with the time was often 
observed. This was due to the fact that the narrow strips, on 
account of the disintegration, soon became thinner in the 
central hottest zone; and uf this was kept at a constant 
temperature by reducing the current, the length over which 
the disintegration took place became constantly shorter. In 
the cases where the disintegration was most rapid, we have 
therefore not used the highest possible temperatures and have 
also reduced the usual 30 minutes time of heating, in order to 
prolong the uniformity of the strips and to enable a greater 
number. of comparisons to be made. Another reason for 
reducing the amount of the disintegration was that the 
tE ansparency of the tube was rapidly destroyed by the metallic 
deposits which had to be frequently removed between the 
observations. 
The weigbings were made on a balance having a sensibility 
about three divisions for O*l mg., and are certain to 
0-01 meg. 

