XX. The common causes of our experiencing more or less heat, or more
or less light from the sun, are the serene or loaded state of the
atmosphere; the oblique direction with which the sun’s rays are reflected
on us; the position, or situation of places; the length or shortness of
the days; the tranquillity or agitation of the winds, and our vicinity
to cold or warm places, such as snowy mountains, or warm subterraneous
effluvia. But, abstracted from any of these sublunary or inferior causes,
I say, that in the sun itself, is contained a cause, that occasions it
to reflect more or less light or heat, and that it actually does reflect
more or less light and heat, at some times than it does at others, and
that this is in virtue of its own proper nature and disposition.
XXI. The reason of which phenomenon is, the transitory spots, which the
astronomers have for some time past observed in the sun. These are a sort
of darkish places, unequal in size and duration, which seem as if they
were on the superficies of the star, and which at different times are
more or less numerous, although it has happened, that for years together
none of them have appeared. Some believe that the antient Chaldeans had
some knowledge of them, for in the Book of Job, we read the following
expression of Job’s friend Eliphaz to him, that the Heavens themselves
are not exempt from their spots: _Cæli non sunt mundi in conspectu
ejus._ On the other hand, the want of telescopes among the ancients, did
not render their making observations on these things impossible; for some
of these spots are so large, as to be visible without a telescope; as
for example that was, which was seen in the year 1706, whose superficies
according to the computation of the astronomers, was thirty-six times
larger than the whole earth; and when they arrive at this magnitude, or
if they are even much less, they may be discerned, by looking at the sun
with a glass tinged with any dark colour.
XXII. But the first person we have any account of, who observed these
spots, was Father Christopher Scheinerus a jesuit, who applied himself
to it with such diligence, that between the years 1611 and 1627 he had
made fourteen hundred observations of them, which he gives an account
of in his _Rosa Ursina_. The celebrated Galileus Galilei began also to
observe them about the same time that Scheinerus did; and since them,
the most laborious astronomers of the last and the present century, have
applied themselves to making the same observations; so that this is a
matter, which at present there is not the least doubt about; and although
some have entertained suspicions whether these spots were in the body
of the sun, or at a little distance from it; others have removed those
difficulties, by demonstrating, that they are inherent in, and exist
on, the superficies of the sun; for they not only revolve in the same
proportion the sun does, but they most probably remain upon it during
the whole time it takes in making an intire revolution, which it does in
twenty-seven days, and they are to be seen compleat for half the time of
that period; which could not happen, if the spots were inferior to the
star.
XXIII. And whether these spots are sooty or smoaky vapours, which arise
from the great furnace of the sun, as some think, or are any other
different thing; it is clear, that during their continuance, the light
and the heat of it reflected on the lower elemental regions, must be
diminished in proportion to the size and number of the spots; and to this
cause may be attributed, some of the notable diminutions of the light and
heat of the sun, which we find recorded in history, provided they were
not occasioned by some obstructions in the atmosphere. Mayolus tells us,
that in the time of the emperor Justinian, the light of the sun for the
greatest part of a year was so dim and faint, that it scarce exceeded
that of the moon; and Plutarch tells us, that at the time of the death of
Julius Cæsar, the light of the sun was equally feeble for a whole year
together; which Virgil also takes notice of in the following verses of
the Second Book of his Georgics:
_Ille etiam extincto miseratus Cæsare Romam_
_Tunc caput obscura nitidum ferrugine texit:_
_Impiaque æternam timuerunt sæcula noctem._