84 
cease troubling ourselves with millions of useless ob- 
servations to be added to millions already existing ? 
No. It is an honest effort, and granting that there 
is surplusage of certain data, the chart is still worth 
while. Besides, there are some by-products of great 
value. To illustrate, a strict verification of the wind 
shifts at San Francisco, a city where the lower air 
circulation is marked, might show a high percentage; 
but this would not be a fair test of the worth of the 
weather chart. Rather, some by-product, as that of 
frost protection. In the first week of January, 1913, 
the general forecaster warned the orange-growers 480 
miles away of impending trouble. Each community 
was warned not once, but day after day, and night 
after night. Fruit worth 10,000,o00l. was in jeopardy. 
Half was saved because of ample, accurate warnings 
coupled with improved methods of heating, covering, 
and protecting. Overtopping the vast saving, was the 
demonstration that protection was effective. The story 
of the campaign against frost extending over a period 
of sixteen years and culminating in the struggle of 
January, 1913, is one of the most inspiring chapters 
in the history of horticulture.. The forecaster not only 
gave warning, but developed the principles of protec- 
tion. At least five basic patents for covering, heating, 
and mixing the air were obtained and donated to the 
public. 
Again, a certain railroad system of the west coast in 
competition with all steam railroads of the United 
States was awarded the Harriman Memorial safety 
medal. In five years not a single passenger’s life has 
been lost through collision or derailment of trains in a: 
total equivalent movement of 8,000,000,000 passengers 
one mile. What has this to do with the weather 
chart ? Only this, that during those five years at 
times of greatest strain, during heavy rains when 
road-beds wash out, and derailments most easily occur, 
the actual head of the whole system kept in closest 
touch with the weather office. Time and time again 
the patrols on thousands of miles of roads were doubled 
on the judgment of the forecaster, based on the 
chart. 
Yet, in San Francisco, it has been known to turn out 
fair when rain was indicated, or some sudden drizzle 
from the sea mar a forecast of fair weather. 
And the conjecture of De Morgan which Mr. Mal- 
lock quotes, ‘‘that Sir George Airy would not have 
given 23d. for the chance of a meteorological theory 
formed by masses of observations,’? remains a con- 
jecture. 
ALEXANDER McADIE. 
Blue Hill Observatory, March 11. 
Origin of Structures on the Moon’s Surface. 
Tue difficulty raised by the Rev. O. Fisher (NATURE, 
February 26, p. 714) with regard to the origin of the 
moon by fission from the earth has been answered 
already in part in Sir George Darwin’s own writings. 
The length of the day when earth and moon revolved 
once a day was calculated by him at first as about 
5 hours, the figure used by Mr. Fisher. Afterwards, 
Darwin showed that taking solar tidal friction into 
account, this period should be reduced to something of 
the order of 24 hours, when the two bodies would be 
almost in contact (see Darwin, ‘Scientific Papers,” 
vol. ii., pp. 323, 364). It may not be amiss to quote 
here his cautious estimate of this result :—‘‘ The whole 
subject is full of difficulties, and the conclusions must 
necessarily remain very speculative.” 
EF. J. M. Strattron. 
Gonville and Caius College, Cambridge. 
March 6, 1914. 
NO. 231 7.7 08r 203] 
NATURE 
[MarcH 26, 1914 
The. Isothermal Layer of the Atmosphere. 
Ir is a commonplace observation that ‘truths of 
science, waiting to be caught,’ are often simul- 
taneously and independently ‘‘caught”’ by two or 
more investigators. One of the most remarkable 
coincidences of this kind appears never to have been 
definitely pointed out as such. This is the recent 
Gold-Humphreys (or Humphreys-Gold) explanation as 
to why the stratosphere is vertically isothermal; viz., 
because of equality in that region between emitted and 
absorbed radiation. This discovery is probably 
destined ‘to remain conspicuous in the annals of 
meteorology for two reasons; first, because of its 
| intrinsic importance, and, secondly, because of the 
following remarkable chronological parallelism in its 
independent development by two investigators :— 
Gold. | 
Preliminary account read | 
at the Dublin meeting | 
of the British Associa- 
tion for the Advance- | 
ment of Science, Sep- 
tember 2-9, 1908. 
Preliminary account re- 
ported in © NATURE, 
October 1, 1908. 
Final paper received by 
Humphreys. 
Preliminary account read 
_ at the Hanover meet- 
ing of the American 
Association for the Ad- 
vancement of Science, 
June 29—July 3, 1908. 
Preliminary account re- 
ported’ . an’. Serence; 
August 21, 1908. 
Final paper sent to the 
the Royal Society of | Astrophysical Journal, 
London, October 5, October ?, 1908. 
1908. 
Final paper read before 
Final paper read before 
the Royal Society of 
the Philosophical 
London, December 10, Society of _Washing- 
1908. ton, D.C., October to, 
1908. 
Final paper published in | Final paper published 
the Proceedings of the in the Astrophysical 
Royal Society of Lon- Journal, vol, xxxix., 
don, A 82, February 16, 
1909. | 
It would be difficult to find a more interesting 
chronological parallel. It is particularly pleasant to 
January, 1909. 
add that the principals, who up to the time of the 
publication of their papers were strangers to each 
other, have since then become well acquainted and the 
best of personal friends. 
C. FirzHuGH TaLMan. 
U.S. Weather Bureau, Washington, March 7. 
Unidirectional Currents within a Carbon Filament Lamp. 
DuRING the past two months I have shown to some 
scores of people the effects described by Dr. Eve under 
the above heading, in Nature of March 12. His 
explanation of the slow creep of the displaced filaments 
back to their original positions does not seem to me 
wholly satisfactory. Other factors governing the 
phenomenon are the electromagnetic attractions be- 
tween the current bearing loops and the plastic yield- 
ing of the heated filament. It was a search for the 
latter effect which first directed my attention to the 
other phenomena. 
The negative discharge from a Wimshurst machine 
also alters the luminosity of the filament, and I have 
observed in some cases (using a modified Fleming 
valve), the complete stoppage of the thermionic cur- 
rent. These two latter effects are now being 
systematically investigated. 
F. Liroyp Hopwoop. 
Physics Department, St. Bartholomew’s Hospital 
Medical College, E.C., March 17. 
