282 
MR. DANIELL ON A NEW REGISTER-PYROMETER 
in a platinum bar. For this purpose I made use of an excellent wind-furnace 
in the Royal Institution, in which upon former occasions hob-nails had been 
completely fused into a button. 
Exp. 19. The register I, which had not been the least injured by the 
previous experiments, was fitted with a new bar of platinum, which had been 
drawn as a wire, was ^ths of an inch in diameter and very ductile. The iron 
bar was also adjusted to a new register, and both were placed upright in a well 
heated crucible. About half an inch of powdered charcoal was strewed upon 
the bottom to prevent any adhesion ; and two soft iron nails, and a piece of 
unglazed Wedgwood’s porcelain, were thrown in for the purpose of affording 
some indication of the degree of heat attained. The crucible was then set in 
the furnace, another smaller crucible inverted upon it, covered with coke, and 
the heat urged to the utmost for two hours. The fire was suffered to burn 
out, and the crucible with its contents removed for examination. It was 
sound, but the luting had been completely fused. The nails were found 
melted into two complete buttons, and the porcelain was partially fused upon 
the surface. 
The register I appeared to be uninjured, but the platinum ring and wedge 
were loose, evidently from a contraction having taken place in the substance of 
the black-lead. This was no doubt owing to the heat having exceeded that at 
which it had been originally baked. The amount of expansion consequently 
could not be measured. The platinum ring, both of this and the other register, 
exhibited a remarkable change of texture ; they had become very rough and 
crystalline, and were perfectly brittle, breaking easily between the fingers. The 
platinum bar also, which there was some difficulty in removing from the 
cavity, presented a very extraordinary appearance. It was apparently em- 
bossed with crystals, and was evidently larger at the lower end than at the 
toj) : it was also something contracted in length. Upon examination with a 
lens no regular facets could be detected, but it had the appearance of a bar 
constructed of plates of native platinum loosely welded together. 
The register which contained the iron bar was considerably bent, and had 
several transverse clefts in its substance, owing possibly to its having become 
inclined in the crucible. Partial fusion had taken place upon the surface of 
the bar, which had run down and formed a knot at its lower extremity. About 
