OcToBER 16, 1902] 
not differing much from 26 days, while Prof. Frank Bigelow, 
using a large quantity of material, finds 26°68 days, and Eckholm 
and Arrhenius return to 26 days, or, as they put it more ac- 
curately, to 25°929 days. The two latter investigators do not, 
however, adopt the idea that this periodicity is due to the 
rotation of the sun. None of these periods can stand the test 
of accurate investigation, 
As the result ot my calculations, I can definitely state that 
the magnetic declination at Greenwich shows no period between 
25°5 and 27°5 days having an amplitude as great as 6” of arcs 
The influence of solar rotation on magnetic variation may there- 
fore be considered to be definitely disproved. 
The intensity of the periodograph increases rapidly with the 
period, and minute variations are, therefore, more easily de- 
tected in short than in longer periods. Six seconds of are forms 
about the limit of amplitude, which can be detected in 25 years 
of observations, when the period is about 26 days; and from 
what has been said above, the amplitude which can be detected 
will be seen to vary inversely with the square root of the time 
interval. For periods of about 14 days, an amplitude of 3” 
of arc is still distinguishable with the material I have used ; 
and such an amplitude is actually found for a period which has 
half the synodic month as its time. The chance that this ap- 
parent variation is due to an accidental coincidence is one in 
two thousand; and I cannot, therefore, assert its definite 
existence beyond all possibility of cavil. But it is surely signifi- 
cant that of all the periods possible between 12°3 and 13°7 days, 
that gives the highest amplitude which coincides with half the 
synodic revolution of the moon. That it is at all possible to 
detect variations of 3” of arc in the observations which are taken 
to 6”, with a probability of error of only one in two thousand, 
is, I think, a proof of the value of the method and the careful- 
ness of the observations. The periodograph has another valuable 
use. It not only gives us the time necessary to establish true 
periodicities of given amplitude, but it also gives us an outside 
limit of the time beyond which an accumulation of material 
is of no further advantage. That limit is reached when the time 
is sufficient to discover the smallest amplitude which the in- 
struments, owing to their imperfections, allow us to detect. 
I am only concerned to-day with a purely statistical inquiry, 
and not with the explanation of any suggested relationship. To 
prevent misunderstandings, however, I may state that I consider 
the possibility of a direct magnetic or electric action of the moon 
excluded ; as regards the latter, the diurnal variations of electric 
potential would be so much affected by a lunar electrification 
sufficiently strong to influence the outbreak of thunderstorms 
that it could not have escaped discovery. We must not, how- 
ever, be dogmatic in asserting the impossibility of indirect 
action. 
out an entirely new field, and we cannot dismiss without re- 
given. Its reality can be decided by observation only. 
No—not by observation only—but by observation supple- 
mented by intelligent discussion; and this brings me to my 
NATURE 
The unexpected discovery of radio-activity has opened | 
617 
advance of knowledge is the chief function of the observer. 
Nevertheless, the President of the Astronomical Department of 
Section A last year (Prof. H. H. Turner) has found it neces- 
sary, in his admirable address, to warn against the danger there 
is that the astronomer should allow himself to be swallowed up 
in a routine work and mere drudgery. The descent is easy : 
You begin by being a scientific man, you become an observer, 
then a machine, and finally—if all goes well—you design a 
new eyepiece. 
If such a danger exists in Astronomy, what shall we say about 
Meteorology ? That science is bred on routine, and drudgery is 
often its highest ambition. The heavens may fall in, but the 
wet bulb must be read. Observations are essential, but though 
you may never be able to observe enough, I think you can 
observe too much. I do not forget the advances which Meteor- 
ology has made in recent years, but if you look at these advances, 
I think you will find that most of them do not depend on the 
accumulation of a vast quantity of material. The progress in 
some cases has come through theory, as in the applications of 
Thermodynamics or through special experiments as by kite and 
balloon observations, and when it has come through the ordinary 
channels of observation, only a comparatively short period of 
time has been ultilised. It would not be a great exaggeration 
to say that Meteorology has advanced in spite of the observations 
and not because of them. 
What can we do to mend matters? If we wish to prepare the 
way for the gradual substitution of a better system, we should 
have some one responsible for the continuation of the present 
one. For this purpose it should be recognised that the head of 
the Meteorological Office is something more than a Secretary to 
a Board of Directors; also that he is appointed to conduct 
Meteorological research and not to sign weather forecasts. The 
endowment of Meteorology should mean a good deal more than 
the endowment of the Telegraph Office which transmits the 
observations. Terrestrial Magnetism and Atmospheric Elec- 
tricity are looked after at present by institutions already over- 
worked in other directions and should be handed over to an en- 
larged Department of Meteorology. Seismology in this 
country now depends on the private enterprise and enthusiasm 
of a single man, andas long as Prof. Milne is willing to continue 
his work, we cannot do better than leave it with him, but some 
permanent provision will ultimately have to be made. 
An improved organisation such as I have sketched out would 
do goud, but could only very slowly overcome the accumulated 
inertia of ages. I should prefer a more radical treatment. 
Organisation is good, but sometimes disorganisation is better. 
Most earnestly doI believe that the subjects of meteorology 
and terrestrial magnetism, and possibly also of atmospheric 
electricity, could be most quickly advanced at the present 
| moment if all observations were stopped for five years, and all 
newed careful inquiry the evidence of lunar action which I have | 
| improved scheme of observation for the future. 
concluding appeal, which I wish to urge upon you with all the | 
legitimate weight of strong conviction and all the illegitimate 
influence of presidential infallibility. 
The subjects with which our subsection is concerned deal 
with facts which are revealed to us by observation more 
frequently than by experiment. There is in consequence a very 
rea] danger that the importance of observation misleads us into 
mistaking the means for the end, as if observation alone could 
add anything to our knowledge. Observation is like the food 
supplied to the brain, and knowledge only comes through the 
digestion of the food. 
and not for some definite scientific object is a useless observ- 
ation. Science is not a museum for the storage of disconnected 
facts and the amusement of the collecting enthusiast. I dislike 
the name ‘‘observatory”’ for the astronomical workshop, for 
the same reason that [ should dislike my body to be called a 
food receptacle. Your observing dome would be useless with- 
out your computing room and your study. What you want is 
an Astronomical Laboratory, a Meteorological or Magnetic 
Laboratory, attaching to the word ‘‘laboratory’’ its true 
meaning, which is a workshop in which eyes and hands and 
brains unite in producing a combined result. 
The problems which confront the astronomer being more 
definite than those of Meteorology, Astronomy has grown under 
the stimulus of a healthy tradition. Hence it is generally 
recognised, at any rate in the principal observatories, that the 
NO. 1720, VOL. 66] 
An observation made for its own sake | 
the energy of all observers and computors concentrated on the 
discussion of the results obtained and the preparation of an 
When we have 
made up our minds what to do with the observations, when we 
have actually done it ; when we know where our present in- 
struments require refining or supplementing, and especially 
when we have found out whether we have not spent much time 
and trouble on unnecessary detail, then the time will have 
arrived jor us to draw up an economical, sufficient and efficient 
scheme of observations. At present we are disinclined to dis- 
continue observations, though recognised as useless, for fear of 
causing a break. We make ourselves slaves to so-called ‘‘ con- 
tinuity,” which is important, but, may be, and I believe is 
being, too dearly purchased. 
There are no doubt some, though probably not very many, 
observations which it is necessary to carry on continuously over 
long periods of time. But at present we are groping in the 
dark, and go on observing everything, and always in the hope 
that some time the observations might prove useful. Our 
whole point of view in this respect wants altering. We should 
fix on our problem first and then provide the observations which 
are necessary for the solution of the problem. Let us restrict, 
in the first instance, the secular observations to the smallest 
number, and concentrate our attention, for short periods of time, 
on some special question. Let us have, for instance, two or 
three years of thunderstorm observations, all countries joining 
in concentrating their energies to the elucidation of all the 
various features of their phenomena. When that is accom- 
plished, it will probably be found that thunderstorms may be left 
to shift for themselves for a wnile, and attention might be 
