1887.J 



On the Heating Effects of Electnc Currents. 



283 



Aluminium. 



Diameter of wire. 



Current in amperes. 



In 



inches. 



In 



Standard 



Flake of 



Wire 



centi- 

 metres. 



"wire 

 gauge 

 !S T o. 



shellac 

 melted. 



red hot. 

 Visible 









in air. 



0-004 



010 



42 



1 -427 | 



(a) 2 -243 



(b) 1 876 



005 



013 



39 



1-851 



2-614 



0-0J7 



0018 



37 



3-138 



3-861 



010 



025 



33 



4-465 



5 632 



012 



030 



30 



6-115 



8-610 



014 



-036 



28 



7-722 j 



(a) 13-200 

 (6) 11-176 



0-013 



046 



26 



8-810| 



(a) 18-823 



(b) 14-602 



0-020 



051 



25 



13 -032 { 



(a) 22-445 

 {b) 17-3S0 



0-026 



0-066 



22 



r 



20 -122 



{a) 35-400 

 \h\ 33-783 



0-030 



0-076 



21 



{ 



(a) 44-240 



(b) 33*790 



Wire 

 fused. 



Fusing 

 current 

 calcu- 

 lated 

 from the 

 formula 

 ad*'*. 



Amperes 



Constant 

 "<z' ? 

 ■when 

 d ex- 

 pressed 

 in inches. 



| 2-536 



2-536 



9023 -3 



4 -023 

 5-712 

 10-138 

 13 "840 



3-549 

 5 -874 

 10 024 

 13 178 



11372 -0 

 9782 -6 

 10132 

 L0523 -0 



[ 16-412 



16-606 



9902 -4 



1 22 -6S8 



24 206 



9389 4 



1 28 -236 



28-360 



9977 3 



1 44 -256 



42-040 



10551 



}49-88 



52 -100 



9597 -2 





Hean = 



10025-0 



Note. — The "wire becomes red, and then immediately much brighter (a dull 

 •white), owing probably to oxidation. To reproduce faint redness without breaking 

 the circuit, the current can be considerably reduced. " a " is the current which 

 caused the first risible rays of light, and so quickly changed the wire to a brighter 

 state of incandescence, while " b " is the reduced current which reproduced the 

 first redness. If the experiment be repeated, the same effects are obtained, although 

 the molecular structure of the wire seems to be much changed by the first heating. 

 After fusing the wire, a white powder, alunuDa, is found, and sometimes a white 

 opaque bead. A wire 18 mils diameter and 10 inches long was raised to faint red 

 with 1122 amperes; it glowed (dull white) on one side of loop with 1158 amperes, 

 and when the heat had apparently spread over the whole length uniformly, redness 

 reappeared, and the current was found to be again 11 22 amperes. The wire was 

 next raised to a moderately white in -andescent state with 15 93 amperes, and with 

 this current broke in two minutes. 



VOL. XLIfl. 



I 



