Juty 30, 1914] 
NATORE 
562 
Kaye and Ewen (Proc. Roy. Soc., June, 1913), 
using an arrangement not very dissimilar to that 
of Dunoyer, obtained some interesting “shadow” 
deposits with iron. One of these, illustrated full 
size in Fig. 2, shows the image obtained by the 
normal interposition of two square-holed dia- 
phragms between a screen and a strip of iron 
heated electrically in a vacuum to 1ooo° C. for a 
few hours. 
This rectilinear projection is probably closely 
associated with what is sometimes termed sput- 
tering, 1.e., the expul- 
sion of molecules, not 
singly, but in relatively 
large aggregates, from 
the surface of hot metals. 
These projected particles 
would, owing to their 
greater mass, be less 
liable to scattering at 
high pressures by the 
surrounding gas mole- 
cules, and so would pre- 
serve their direction of 
flight longer than parti- 
cles with dimensions not 
far from molecular. 
Fig. 3 is a photomicrograph (taken by Mr. 
Ewen, Zeit. f. Metallographie) showing the pits 
which developed in the surface of a specimen of 
wrought iron when heated for about 4 hours at 
1000° C. in a vacuum. 
There are grounds for suspecting that the 
mechanism of sputtering is partly electrical, for 
it was found that the passage of the heating 
current through the specimen itself predisposed 
the metal to more rapid disintegration than if it 
Fic, 1.—D.pysit cast _y heated 
copper strip, cruciform in 
shape, on screen 1 mm, away. 
Fic. 2.—Photograph of diaphragm (on left) and iron 
deposit cast by it. Full size. 
were heated under the same conditions in a 
furnace. 
The practical study of high-temperature 
furnace experiments on thermionics finds raison 
d’étre, if such were needed, in its applicability 
to the problems of solar electricity. If it may be 
regarded as legitimate to extrapolate from the 
results obtained over the range of temperatures 
(up to 3000° C.) possible in the carbon resistance 
furnace, then it would appear that at the esti- 
mated temperature of the sun (5500° C.) the elec- 
NOM2335, VOL. O32] 
| 
trical emissions would amount to many millions 
of amperes. Thus, notwithstanding the gigantic 
areas of sun-spots, there is no difficulty in ac- 
counting for the enormous Currents necessary to 
produce the magnetic fields (from 2000 to 5000 
gauss), which Hale has shown to be associated 
with the whirlpools in sun-spots. On the same 
lines, we may seek to explain also the sun’s 
general magnetism, the vertical component of 
which at the poles is estimated by Hale at about 
50 gauss. 
In conclusion, we may refer briefly to two 
practical developments of the study of the molar 
and electric emissions from hot metals. The half- 
watt lamp and the new Coolidge X-ray tube are 
first-fruits culled by observers equipped with a 
knowledge of the results of pure research, and 
| 
- t 
Fic. 3.—Photomicrograph of surface of iron strip which has 
been heated zz vacuo, showing pits produced by volatilisa- 
tion. X1400. 
an ability to apply them to industrial require- 
ments. The work, carried out at the General 
Electric Co.’s research laboratory in Schenectady, 
is worthy of the attention of those among us 
who, severely practical and immediately utili- 
tarian, seek to deprecate the study of pure science 
in this country. G. W. C. Kave. 
A FORGED “ANTICIPATION ” OF MODERN 
SCIENTIFIC IDEAS. 
Te the 1913 presidential address to the Linnean 
Society, noticed in Nature for January 22, 
1914, Prof. Poulton gave an account of an Ameri- 
can booklet by G. W. Sleeper, dated 1849. The 
work, if genuine, was an extraordinary anticipa- 
