•270 
MR. DAN I ELL ON A NEW REGISTER-PYROMETER 
From the real expansion 02914 
Deduct the apparent expansion obtained by the pyrometer .02036 
The remainder .00878 
is again the expansion of the black-lead as obtained by this series of experiments. 
Expansion of 6.5 inches of Black-lead. 
From 64° to 660° by platinum bar 00784 
by iron bar 00878 
Mean .00831 
either determination differing- from the mean by less than j^dths of an inch. 
This close agreement in results from two metals whose expansions differ so 
much from each other is highly satisfactory; but the great delicacy of the 
instrument may be still better appreciated from the following experiment of 
the expansion of nine different metals from the temperature of 62° (the tem- 
perature of the air at the time of observation) to 212°. 
Exp. 3. Bars of the following metals were successively placed in the register 
and immersed in hot water, which was gradually heated to the boiling point, 
and kept boiling for ten minutes in each instance. The following Table ex- 
hibits the readings of the scale and the appropriate expansions. 
Platinum 
Iron (soft) 
Copper . 
Tin (grain) 
Zinc . . 
Lead . . 
Brass 
Gold (fine) 
Silver (fine) 
Table V. 
6 19 = .00276 from 60° to 2 12° 
0 35 = .00508 
0 47 = .00683 
0 56 = .00814 
1 40 = .01454 
1 25 = .01223 
0 55 = .00799 
0 36 = .00552 
0 56 = .00814 
Iu the subsequent Table I have given the absolute expansions of the same 
metals from 32° to 212° from the best authorities ; and for the sake of compa- 
