528 
perature being recovered as well as the volume. The 
sole result of the cycle is that heat is raised from a 
lower to a higher temperature. Since this is assumed 
to be impossible, the supposition that the operations 
can be performed without external work is to be 
rejected—in other words, we must regard the radia- 
tion as exercising a pressure upon the moving piston. 
Carnot’s principle and the absence of a pressure are 
incompatible. 
For a further discussion it is, of course, desirable 
to employ the general formulation of Carnot’s prin- 
ciple, as in a former paper.* If p be the pressure, 
@ the absolute temperature, 
a Pen poe) 0-12); 
where Mdv represents the heat that must be com- 
municated, while the volume alters by dv and dé=o. 
In the application to radiation M cannot vanish, and 
therefore p cannot. In this case clearly 
M=U+p. (30), 
where U denotes the volume-density of the energy— 
a function of @ only. Hence— 
A es Aa ae 15) 
If we assume from electromagnetic theory that 
p=3U (32), 
it follows at once that 
Uc (33), 
the well-known law of Stefan. 
In (31) if p be known as a function of 6, U as a 
function of @ follows immediately. If, on the other 
hand, U be known, we have 
and thence 
» + (34). 
RAYLEIGH. 
** Atmospherics ’’ in Wireless Telegraphy. 
THE greatest difficuity in wireless telegraphy is due 
to atmospherics. I believe that every attempt to pre- 
vent these sudden shocks from entering the receiving 
apparatus in important stations has failed. Now Mr. 
5. G. Brown has wires stretched horizontally from 
his house to his stables in Kensington at about 4o ft. 
from the ground; he receives all the ordinary messages 
and time signals with practically no sign of atmo- 
spherics. Of course, lessening the height of high 
antennz lessens the energy received, but it seems 
that the diminution of the blow is much greater than 
the diminution of ordinary signals. One of Brown’s 
latest relays magnifies the currents in the receiving 
apparatus one hundred times, and he expected that 
the signals would be well received, in spite of the 
lowness of his wires, but he was surprised to find 
that the blow, the atmospheric, had almost altogether 
disappeared. In fact, there was no blow to magnify. 
I believe that the Salcombe Hill Observatory arrange- 
ment for receiving time signals is also free from atmo- 
spherics, its antennz being quite low, and a Brown 
relay being used. 
If the following explanation of this curious pheno- 
menon is correct, it ought to be easy to destroy 
atmospherics however high the antennz may be. 
An antenna is affected by rays of all frequencies 
because its vibrations are damped by resistance, 
_3 “© On the Pressure of Vibrations,” P/i2. Mag., iii., p. 338, 19 2; "Scien- 
tific Papers,” v., Pp. 47+ 
NO. 2306, VOL. 92] 
NATURE 
ee a ee eee 
[January 8, 1914 
although it is, of course, most sensitive to rays of its 
own frequency. An atmospheric is of the nature of a 
sudden shock; it consists of ‘rays of all frequencies, 
and particularly of rays of all sorts of very high © 
frequencies. Suppose the frequency of the antenna ~ 
to be anything from 50,000 to 300,000 per second; let 
us say 100,000. I take it that houses and trees are 
very imperfect antennz the frequencies of which are 
probably much greater than 100,000 generally, 
although sometimes less. When rays are proceeding 
horizontally the ther in the neighbourhood of trees 
and houses is therefore greatly robbed of all energies 
which accompany waves of high frequency. In fact, 
all rays of frequencies corresponding to the frequen- 
cies of trees and houses are absorbed, and a low 
antenna of frequency 100,000 receives but little energy 
of other frequencies than its own, and therefore little 
of the ‘‘atmospheric ” blow. If this explanation is 
correct, it is only necessary to surround a receiving 
antenna by numerous others of all sorts of high 
frequency. If I am right it is scarcely possible to 
receive atmospherics in the middle of a large city 
unless the ground is much higher than neighbouring 
ground, just as we know that an ordinary house in 
the middle of a city is never struck by lightning. 
My explanation cannot be complete, for the man 
in charge of a coast station in the Mediterranean states 
that he has difficulty in receiving signals because dis- 
turbing atmospherics are so numerous, whereas ships" 
in the neighbourhood, or even five miles away, are 
comparatively undisturbed in their signalling. Now 
these ships are far away from trees and houses. 
Again, Mr. Brown tells me that although he receives 
no atmospherics from great distances, his signals are 
certainly disturbed by local thunderstorms. In fact, 
he can predict the coming of a thunderstorm when 
it is probably twenty miles away. My explanation 
may be defended by saying that the fronts of the 
Maxwell waves are not vertical in such cases. Again, 
I have been told that without altering the antenna 
at a receiving station, if we tune it to a lower fre- 
quency, there is more disturbance from atmospherics. 
It is possible that this is not generally true, but only 
true for certain stations, and, if so, my explanation 
may escape censure. Joun Perry. 
December 30, 1913. 
Columbium versus Niobium. 
Ar a meeting of the council of the International 
Association of Chemical Societies in Brussels, last Sep 
tember, a committee on inorganic nomenclature, among 
other recommendations, endorsed the name and symbol 
“niobium”? and ‘Nb,’ for the element which was” 
originally named columbium. As this recommendation 
is historically erroneous, a brief statement of the facts 
appears to be desirable. : 
In 1801 Hatchett, an English chemist, analysed a 
strange American mineral, and in it found a new 
metallic acid, the oxide of an element which he named 
columbium. A year later, Ekeberg, in Sweden, 
analysed a similar mineral from Finland, and dis- 
covered another element, which he called tantalu 
Wollaston, in 1809, undertook a new investigation of 
these elements, and concluded that they were identical 
a conclusion which, if it were true, would have 
involved the rejection of the later name, and the 
retention of the earlier columbium. The accepted 
rules of scientific nomenclature make this point clear. 
For more than forty years after Hatchett’s discovery 
both names were in current use; for although Wollas 
ton’s views were accepted by many chemists, there 
were others unconvinced. In 1844, however, Heinrich 
Rose, after an elaborate study of columbite and tanta 
lite from many localities, announced the discovery of 
