314 Dr. Herschei/s Observations to investigate 
sun, contains five very irregular and very unequal periods.* The 
first takes in a series of 21 years, from 1650 to 1670, both in- 
cluded. But it is so imperfectly recorded, that it is hardly safe to 
draw any conclusions from it; for we have only a few observa- 
tions of one or two spots that were seen in all that time, and those 
were only observed for a short continuance. However, on 
examining the table of the prices of the quarter of nine bushels 
of the best or highest priced wheat at Windsor, marked in Dr. 
Adam Smith’s valuable Inquiry into the nature and causes of 
the wealth of nations, we find that wheat, during the time of 
the 21 years above mentioned, bore a very high price; the 
average of the quarter being £2, 10s. 5\\d. This period is much 
too long to suppose that we might safely compare it with a 
preceding or following one of equal duration. Besides, no par- 
ticulars having been given of the time preceding, except that 
spots in the sun, a good while before, began to grow very scarce, 
there might even be fewer of them than from the year 1650 to 
1670. Of the 21 years immediately following, we know that 
they certainly comprehend two short periods, in which there 
were no spots on the sun ; of these, more will be said hereafter; 
but, including even them, we have the average price of wheat, 
from 1671 to 1691, only £ 2. 45-. 4 ^d. the quarter. The dif- 
ference, which is a little more than as 9 to 8, is therefore still 
a proof of a temporary scarcity. 
Our next period is much better ascertained. It begins in 
December 1676, which year therefore we should not take in, 
and goes to April 1684 ? i n which time, Flamsteed, who was 
then observing, saw no spot in the sun. The average price of 
wheat, during these 8 years, was £ 2. 7 s. 7 d, the quarter. We 
* See Astronomie par M. De la Lande, § 323?- t See Book I. Chap. XI. 
