654 REPORT—1899. 
The author now finds that N,, is composite, containing the factors 319,489 and 
974,489; also that (most probably) there are no more prime factors < cne 
million of any Fermat’s Number (other than those now known to be contained in 
the above-named eleven numbers); this last result requires confirmation by an 
independent computer. 
DEPARTMENT II.—METEOROLOGY. 
1. Interim Report on Solar Radiation. See Reports, p. 159. 
2. On a Connection between Sunspots and Meteorological Phenomena. 
By Dr. Van RisCKEVORSEL. 
If from a sufficiently large number of years the mean temperature for each day 
is computed, and if these means are—generally after more or less smoothing— 
plotted down in a curve, this will be found to be no smooth curve. It will show 
a great number of secondary maxima and minima. Now, on the one hand, these 
seem to be sensibly the same all over our globe. On the other hand, if we treat in 
the same way the barometer readings, the wind pressure, the rainfall, the magnetic 
phenomena, we always find the same result ; a curve, very different from others 
often in a general sense, but showing maxima and minima about the same 
dates. 
The phenomenon is not in each single case very striking ; in some cases there is 
very slender evidence of it indeed. But few of our series of observations as yet. 
are long enough and good enough, and there is in each case evidence enough to 
hope that as soon as this will be the case the phenomena will be apparent enough 
throughout. 
This renders it probable that the cause of these irregularities is not terrestrial. 
It was natural to look in the first place to the sun-spots for an explanation. The 
relative numbers of sun-spot frequency for the fifty years 1849-1898 were plotted 
down in a curve, and the temperature of each day of the year for the same period 
as observed at the Helder in another curve. The resemblance between both 
curves is striking. With the exception of two or three out of some twenty-five, all 
the notches of one curve correspond to similar features in the other. Moreover 
nearly without an exception each maximum or minimum of the temperature 
occurs a couple of days later than the corresponding sun-spot one. These facts 
seem to point towards a decided relation between the two phenomena. 
Next the sun-spot numbers as well as the mean temperatures were plotted 
down, arranged in Mercury years. The two curves thus obtained also show a 
decided relation. 
The next step will be an investigation as to a possible influence of the revolu- 
tion of Venus. As to Mars, it is not probable that the series of yearsis long enough 
to give more than an indication of such an influence—if even that. 
3. Report on Seismology. See Reports, p. 161. 
4, Seismology at Mauritius. By T. F. Cuaxton, F.R2.A.8. 
A Milne’s seismograph for recording unfelt earth movements has been at work 
at the Royal Alfred Observatory, Mauritius, since September 1898. 
All the seismograms have been tabulated and subjected to analysis, and the 
results will be published as soon as possible. 
