san NATURE 
VERY HIGH TEMPERATURES.* 
jE HOPS. a century ago this month Michael 
~ Faraday entered the Royal Institution for the 
first time. He was then a youth of twenty, in the 
last year of his apprenticeship to a bookbinder in 
Blandford Street. Among the meagre records we 
possess of Faraday’s early life we find the follow- 
ing :— 
“J had the good fortune, through the kindness of 
Mr. Dance, who was a custtumer in my master’s shop 
and also a member of the Royal Institution, to hear 
four of the last lectures of Sir Humphry Davy in 
that locality. The dates of these lectures were 
February 29, March 14, April 8 and ro, 1812.” 
It was Faraday’s habit to occupy the seat in the 
gallery over the clock. He made very full notes of 
the lectures, and afterwards wrote them up, indexed 
and bound them with his own hands into a volume 
of 300 pages, which is now preserved at the Royal 
Institution.? 
Some months later Faraday writes :—‘‘ Under the 
encouragement of Mr. Dance I wrote to Sir Hum- 
phry Davy, sending, as a proof of my earnestness, 
the notes I had taken of his last four lectures. The 
reply was immediate, kind, and favourable.” 
In March, 1813, apparently largely on the strength 
of the impression made upon Davy by this volume of 
notes, Faraday was engaged as assistant in the 
laboratory of, the Royal Institution at a salary of 25s. 
a week, with two rooms at the top of the house. 
The first lecture of Davy’s course referred to was 
on ‘Radiant Matter,’’ and dealt, among other things, 
with the action of electric sparks on gases. Ever 
since Volta’s discovery in 1800 Davy had_ been 
occupied with the study of the pile and the effect of 
the new currents in producing heat and chemical 
change, thus leading up to his decomposition of the 
fixed alkalies and the isolation of potassium in 1807. 
Following on this discovery, Davy proposed that a 
fund ‘‘should be raised by subscription for the con- 
struction of a large and powerful battery, worthy of 
a national establishment, and capable of promoting 
the great objects of science, and that this battery be 
erected in the laboratory of the Royal Institution.” 
The sum required, a little more than sool., was soon 
got together, and at the concluding lecture of the 
1812 season the battery was put in action for the first 
time. We read in Davy’s ‘‘Elements of Chemical 
Philosophy,” iv., p. 110, an account of how he applied 
the battery to the running of an electric ‘‘ arch” 
between two carbon rods. Parts of Davy’s battery 
are still preserved at the Royal Institution.* 
I begin my lecture thus merely to emphasise once 
more the truth of the adage of 3000 years ago: 
‘There is no new thing under the sun.”’ 
In 1912, when considering the subject of ‘very 
high temperatures,’ we can claim, comparatively 
speaking, to be capable of little more than Davy 
accomplished a century ago. In his arc he melted 
all the most infusible materials known to him, 
including lime and magnesia, which are among the 
most refractory materials in use at the present day. 
Turning now from the historic to the present aspect 
of our subject, permit me to begin with a few 
elementary considerations as. to our conception of 
temperature. I think I -am correct in saying that 
everyone has some idea in his own mind of a tempera- 
ture scale, a kind -of intuition which is generally a 
fairly useful one for practical purposes. Probably 
I-am not exaggerating when I say that even. men of 
science, who always think for their professional pur- 
1 Abridged from a discourse delivered at the Royal Institution on 
February 9 by Dr. J. A. Harker, F.R.S. 
2 Exhibited on the lecture table. 
NO. 2229, VOL. 89| 
[Jury 18, 1912 
poses of temperatures on the centigrade scale, find 
themselves obliged to convert to Fahrenheit for an 
idea of the temperature of a room or of a summer’s 
day. 
I have endeavoured to give a graphic representa- 
tion (Fig. 1) of the temperature 
scale as we know it, both in 
centigrade and Fahrenheit de- 
grees. You will notice the small- 
ness of the interval between the 
extreme temperatures that prevail 
in the arctics and the tropics, 
and how restricted the ‘cold ”’ 
region down to absolute zero is 
compared with the possibilities in 
the other direction. While, on 
the one hand, Kammerlingh 
Onnes by the evaporation of 
liquid helium under low pressure 
has succeeded in getting during 
the last few weeks to within 
yi? C. of absolute zero, the 
highest recorded terrestrial tem- 
perature—that of an electric arc 
under high pressure—falls short 
of the sun’s estimated tempera- 
ture by some 2000° C 
Some landmarks in our avail- 
able range of temperature are 
given in Table I. It may be re- 
marked that the three substances 
last quoted in the table are all 
in extensive use for electric lamp 
filaments. 
TEMPERATURE 
OF TRE SUN 
ig 
z 
he 
fe 
- 
iS 
z 
r 
= 
$ 
2 
& 
: 
S 
Fd 
é 
4 
3 
: 
: 
. 
iy 
Taste I1.—Various Temperatures. | 4 3 
§Deg. C. 5. * , 
Absolute zero : — 273 =" eis 
Helium boils (02 mm.) = 272 Fs | 2 
fs 5, (760 mm.) — 269 2 Fd 
Hydrogen boils = 253 z = 
Oxygen boils — 183 6 é 
Carbonic acid boils =e 
Mercury freezes - 39 
Water freezes “ ae ° 
Water boils ... 100 
Tin melts... aoe = 232 
Lead melts ... oo 327 
Mercury boils vee iy 357 
Zinc melts 419 
Sulphur boils 445 
Aluminium melts 657 
Common salt melts Sor 
Zinc boils g18 
Silver melts 961 
Gold melts ... 1062 
Copper melts 1083 
Cast-iron melts about I100 
Pure iron melts 1500 = 
Fire bricks soften ... 1400-1800 i 
Silica softens . 1500-1600 |- & 
Platinum melts 1750 \q E | 
Silver boils 1950 Ea sal 
Tin boils 2270-—Cs« | ES 
Copper boils : ne 2310 ul 
Lime and magnesia melt about 2400 Bo 
Iron boils = 2450 =o ui 
Tantalum melts about 2900 aN 
Tungsten melts 33 ., 3000: 
Carbon, melts ts A ? 
’ 
Table II. gives examples of various flame tempera- 
tures which we have at our disposal. 
