448 
MR. j. t. bottomlet ox thermal 
Asymptotic Experiments, March 25 to March 30, 1887. Slider at 450 of scale. 
Temperature of wire, 505° C. 
Tempera + uie 
of water- 
jacket. 
Pressure. 
Current. 
C 2 R/Jx. 
Total emission divided by 
lowest emission observed, 
(726 - l x 10 —4 ), taken as unity. 
°C. 
Amperes. 
17 
•094 
0-9400 
1688 xIQ" 4 
2-324 
•053 
•8106 
1255 „ 
1-728 
•034 
•7675 
1126 „ 
1-551 
■019 
•7201 
990-3 ., 
1-363 
•013 
•6942 
920-4 „ 
1-267 
•on 
•6899 
909 0 „ 
1-242 
•0071 
•6597 
83P4 „ 
1444 
•0046 
•6468 
798-7 „ 
1400 
•00052 
•6339 
767-4 „ 
1'056 
•00019 
•6252 
746-4 „ 
1-028 
* 
•6446 
793-6 „ 
1093 
* 
•6338 
767-0 „ 
1-056 
* 
•6252 
746-4 „ 
1-028 
•6230 
741-3 „ 
1-021 
t 
•6209 
736-2 „ 
1-014 
•6187 
7311 „ 
1-007 
•6166 
726 1 „ 
1-0 
It only remains for me to give a brief account of experiments commenced on 
radiation from various surfaces in liigdi vacuum. On this important subject I have, 
up to this time, been only able to touch very lightly by experiment; but I hope 
before long to be able to offer a communication on the subject. Figs. 5a, 5b, Plate 24, 
show an apparatus which I am using. A platinum wire, ctb, is held, stretched 
between two spiral springs, in a glass tube. The outer ends of the spiral springs 
terminate in loops; and two pieces of glass rod, which are passed into tubes cc, c'c', 
pass through the loops, so that the springs pull on these glass rods. After the rods 
have been passed into their places, the ends of the tubes cc, cc', are closed up, except 
one which is used for exhausting. Flexible copper electrodes are soldered to the loops, 
and are silver-soldered to stout multiple platinum terminals; and by means of these, 
which are fused with the help of some white enamel into the glass at d, cl, the 
current is passed through the platinum wire. At e, e, e, platinum wires are brought 
through the sides of the tube and serve as potential electrodes ; and it is to keep the 
platinum wire ctb in the middle of the length of the tube, and to avoid pulling 
unduly on the potential electrodes, that the two spiral springs, one at either end of 
the tube, are employed. 
The two halves of the platinum wire cib are differently treated as to surface; 
for example, I am at present experimenting on a wire, one half of which is brightly 
* Pressure not measured, but gradually diminishing. 
t Pressure coming down ; during 1| liour radiation gradually fell to lowest figure given, and then 
remained unaltered. 
