398 
On the Application of Solar Physics . [July, 
other publications emanating from Zurich. Then as regards 
Austria, there was the “ Zeitschrift der osterreichischen 
Gesellschaft fur Meteorologie,” the “ Denkschrift der Wiener 
Academie,” and other works ; as regards France, the 
“ Comptes Rendus” ; and as regards Belgium, the <c Me- 
moires de l’Academie Royale de Bruxelles.” 
It however requires, I think, but a cursory glance over 
these endless papers, to show that the tabulation of sun-spot 
phenomena has at length taken a certain definite shape, and 
that the chief results are already known. But what is not 
a little curious, it will at the same time be discovered that 
certain outstanding questions have arisen out of the enquiry 
where a difference of opinion is expressed. Take, for ex- 
ample, the question — Is the sun hottest when it has fewest 
or most spots on its face ? This looks simple, and yet some 
argue one way and some the other. Are the spots a defect 
in the photosphere, or are they the indications of a period 
of solar energy ? Experiments with the black bulb thermo- 
meter, between the years 1837 and 1869, brought Prof. 
Piazzi Smyth to the conclusion that at Edinburgh a great 
heat-wave occurs every eleven years and a fraction, its max- 
imum slightly lagging behind the minimum of the sun-spot 
cycle. Mr. E. J. Stone, at the Cape of Good Hope, from 
the temperature observations recorded during thirty years, 
came to a similar conclusion ; and Dr. W. Koppen, in his 
elaborate paper, finds that in the tropics the maximum of 
warmth occurs a full year before the year of minimum sun- 
spots, while in zones beyond the tropics it falls two years 
after the minimum. This would incline us to the opinion 
that the period of fewest sun-spots is the warmer of the two, 
which is certainly the impression on the writer’s mind ; but 
let us look to the physical side of the question. 
The heading of the physical enquiries from which opinions 
on the subject may be drawn are, of course, the winds and 
rains, the seasons and agriculture, and the magnetic and 
seismic phenomena. First, the winds and rains : these, as 
is generally admitted, come on at the period of most sun- 
spots ; 1879 is an example of a disastrous and wet season 
occurring at such a period. Some say wind and rain mean 
that the sun has then greater energy; but it must be added 
that this does not so clearly make out a case of greater heat, 
since cold is likewise an essential to locally condense the 
atmosphere, and so to raise the wind and saturate the air. 
We may illustrate this point by remarking that wind and 
rain are characteristic of the colder, and not the warmer, 
portion of the year. Then magnetic disturbances likewise 
