NAPOKE 
[ FEBRUARY II, 1904 
Qin. 
352 
‘With regard to the contemporary severity and mild- 
ness of the seasons, it will hardly be necessary to remark 
that nothing decisive can be obtained. An indirect source 
of information, however, is opened to us by applying to 
the influence of sunbeams on the vegetation of wheat in 
this country. I do not mean to say that this is a real 
criterion of the quantity of light and heat emitted by the 
sun, much less will the price of this article completely re- 
present the scarcity or abundance of the absolute produce 
of the country. 
‘On reviewing the period 1650-1713, it seems probable, 
from the prevailing price of wheat, that some temporary 
scarcity or defect of vegetation has generally taken place 
when the sun has been without howe appearances which 
We surmise to be symptoms of a copious emission of light 
and heat. 
“To those acquainted with agriculture who may remark 
that wheat is well-known to grow in climates much colder 
than ours, and that a proper distribution of rain and dry 
weather are probably of much greater consequence than the 
absolute quantity of light and heat derived from the sun, 
I shall only suggest that those very circumstances of proper 
alternations of rain and dry weather and wind, &c., favour- 
able to vegetation, may possibly depend on a certain 
quantily of “sunbeams being supplied to them.’ 
Herschel’s suggestion was a daring one, for however 
perfect our national statistics may have been in relation to | 
the price of wheat, there was nowhere kept up a continuous 
record of the changes observable on the sun’s surface, nor 
had there been any serious aitempt made to determine the 
law underlying them. 
In 1825 this serious attempt was made, and by Schwabe, 
of Dessau, who discovered a cycle of about eleven years in 
the solar changes. Wolf afterwards took up the question. 
Herschel had associated the variation in the number of 
spots with that in the price of corn, the connecting link 
being sunshine or weather. It was to him a question of 
meteorology. 
A year after the publication of Herschel’s papers, 
Wollaston extended the early spectrum work of Ree and 
Newton by discovering 
many dark lines; these were for the first time mapped by 
Fraunhofer in 1814. 
Soon after 1850 it became a question of the connection of 
sun-spots with terrestrial magnetism as well as with meteor- 
ology. A new idea was introduced. 
Lamont, Sabine, and Allan Broun discovered that there 
was a well marked coincidence between the variations of 
magnetic effects, as observed on the surface of our planet 
by delicately suspended magnets, and the quantity of spotted 
area observed on the sun. This in later telegraphic days 
is not merely a pious opinion which does not interest any- 
body, because, when the magnetic changes are very con- 
siderable and the disturbances arrive at a maximum, it is 
very difficult to get a telegram from London to Brighton. 
The period around the year 1860 was rendered ever 
memorable by a still further extension of Kepler’s and 
Newton’s work, which at once explained the dark lines 
observed in the solar spectrum by Wollaston and Fraunhofer. 
Hitherto undreamt-of attacks on the nature of the sun 
became possible. The names of Kirchhoff, Bunsen, 
Angstrom, Stokes, Balfour Stewart will go for very long 
down the stream of time, because they showed us that in 
spectrum analysis we had the power of practically con- 
versing, chemically, with the distant worlds in space, and 
these distant worlds, of course, included the sun, although 
it is practically our neighbour. 
It was now established that the solar radiation came from 
the incandescence of metallic vapours and gases in the sun’s 
atmosphere, the metals and gases being for the most part 
those with which we are familiar on the earth. Not only 
was a high temperature demonstrated in this way, but it 
was further shown that above the sun’s apparent surface 
there was an absorbing atmosphere, consisting of vapours 
cooler than those below, but yet hot enough to be composed 
of the steam of iron and other metals. 
In 1865, De la Rue, Stewart, and others, in an attempt to 
get the periodicity of the solar phenomena still more 
accurately determined, started work at Kew; while the 
former observations were carried on by Schwabe and Wolf 
NO. 1789, VOL. 69| 
that in the solar spectrum there were | 
by the eye, photography, which was then being introduced 
into astronomical work by the labours of Warren De la Rue, 
was for the first time now utilised, and a picture of the sun 
was taken each day. 
In 1866 a new method of observing solar changes, which 
consisted in throwing an image of the sun on the slit plate 
of a spectroscope, revealed the fact that the spectra of spots 
differed from that of the photosphere generally ; certain lines 
were widened in the spot spectrum (Lockyer, Proc. Roy. 
Soc., October 11, 1860). 
In 1867 a connection between changes in spotted ar 
in terrestrial temperatures was pointed out by Baxendell 
(Memoirs of the Manchester Lit. and Phil. Soc., third 
series, vol. iv., pp. 128 et seq.). He noticed a distinct and 
very striking relation between the number of sun-spots and 
the ratio which exists between the difference of the mean 
maximum temperature of solar radiation and the mean 
maximum air temperature on the one hand, and that of the 
mean temperature of the air and of evaporation on the 
other. 
In 1868 a spectroscopic method was discovered of obsery- 
ing in full daylight the ‘t prominences’ or ‘* red flames ”” 
which hitherto had only been glimpsed during eclipses, and 
it was established that, closely surrounding the sun 
ordinarily seen, there was an envelope, named the chromo- 
sphere, of incandescent gases and vapours, hydrogen, and 
a new substance named helium chief among them (Lockyer, 
Proc. Roy. Soc., October 20, 1868). 
Many spectroscopic observations made on the spots and 
prominences about this time indicated great changes in the 
solar temperature in different regions, and possibly, there- 
fore, changes in the amount of heat radiated earthwards. 
From the changes thus actually seen it was easy to imagine 
that there might be a cycle of terrestrial changes depend- 
ing no longer on the sun’s presentation to us in its daily 
and vearly rounds, but on physical changes in the sun itself, 
requiring, perhaps, many years to accomplish. 
In 1869 Janssen showed (Comptes rendus, vol. xviii. 
(1869), pp. 367 et seq.) that by a special arrangement of the 
spectroscope an image of the sun, showing the prominences 
both on the disc and surrounding it, might be obtained. 
It was not very long before it was found that the reaction 
of these solar changes on the earth was not so limited as 
had formerly been ‘thought. This was an idea started by: 
Dr. Stone, of the Royal Observatory at the Cape of Good 
Hope, Piazzi Smyth, of the Royal Observatory of Edin~ 
burgh, and others, about the years 1870 and 1871, but the 
most striking Imperial contribution to the matter we owe 
ea and 
to the labours of a distinguished meteorologist, Dr. 
Meldrum, director of the observatory at Mauritius, which 
has since become the Royal Alfred Observatory. He showed 
that the number of wrecks which came into the harbour of 
the Mauritius and the number of cyclones observed in the 
Indian Ocean could enable anyone to determine the number 
of spots that were on the sun about the time. The Mauritius 
is most admirably suited for the making of these observ- 
ations, because the tropics are really the right region in 
which to try and estimate the possibilities of this solar 
action. Meldrum found, in fact, that the maximum number 
of cyclones was associated with the maximum number of 
sun-spots. He wrote (Nature, vol. vi. p. 357, 1872) :— 
“During the period 1847-72 it is found that some years 
have been remarkable for a frequency, and others for a 
comparative absence of cyclones. 
ce 
1847-51 were characterised by cyclone frequency. 
“1852-57 5, 5 », Comparative calm. 
“1858-63 cyclone frequency. 
~, 1864-68, P decrease. 
“* 1868-72 ,, ; great increase. 
““Tt will be seen that the years correspond with the 
maxima and minima epochs of sun-spots. It appears to me 
that there is more than a mere coincidence as to time. 
“The numbers of wrecks during these periods also show 
a similarly regulated frequency.’ 
Poey, investigating shortly afterwards the cyclone con- 
dition in the West Indies (Comptes rendus, November 24, 
1873, P- 1222), found that the greater number of years of 
maxima of storms fall from six mOnthe to two years, at the 
most, after the years of maxima of solar spots. 
