278 
MR. DANIELL ON A NEW REGISTER-PYROMETER 
and retained the form of the bar like a sharp cast, and left the surface of the 
register perfectly clean and bright. The arc measured after the experiment 
was 6° 16' = expansion .0546. Part of the lump of metal remained unmelted. 
Exp. 15. Another register, which had been prepared with the iron bar, was 
immediately immersed in the fluid metal. The fire, however, had been allowed 
to fall, and the iron almost instantly congealed ; and in attempting to lift the 
register out, it was found to be set fast and broke. The experiment was so far 
instructive, that it proved how nearly the exact melting point had been attained 
in the preceding experiment. The iron bar was removed uninjured. 
Exp. 16. The register I with the platinum bar was boiled in mercury for 
ten minutes: the arc afterwards measured was 1° 20' = expansion .0116. 
Exp. 17- About 30lbs. of zinc were carefully melted in a crucible set in a 
common fire, assisted with the bellows. The register A was prepared with the 
iron bar and held down in the metal, which was supplied from time to time so 
as to insure its very gradual fusion, and some portion always remaining in the 
solid state. In ten minutes time it was removed, and when cold the arc mea- 
sured was 2° 45', equivalent to an expansion of .0239. 
A dry stick of deal plunged into the melted metal for a few seconds caused 
a violent ebullition, and was deeply charred. The zinc in this state did not 
appear red in the light. 
Exp. 18. About 12lbs. of zinc were melted in a smaller crucible: the re- 
gister B prepared with the iron bar was immersed in it ; but instead of being 
gradually supplied, the heat was allowed to increase after fusion till it began to 
burn : at this point there was an evident blush of red upon its surface. The 
arc measured upon this occasion was 4° 7 f = expansion .0358. 
I shall now collect together the results of the preceding experiments, for the 
purpose of showing what conclusions may be derived from them with regard 
to the degrees of temperature which they indicate when referred to the com- 
mon thermometric scale. I shall make the calculations first upon the suppo- 
sition that equal amounts of expansion denote equal increments of tempera- 
ture; and I shall thus be enabled to compare the present series with that 
which I formerly obtained with my first pyrometer, and to offer a few remarks 
upon the differences of the two. 
I shall adopt the corrected temperature of 662° 135 0° Centigrade) for the boil- 
