“The spots are, undoubtedly, closely connected with the formation of faculæ, for I have often observed faculæ, or narben, formed at the same points from whence the spots had disappeared, while new solar spots were also developed within the faculæ. Every spot is surrounded by a more or less bright, luminous cloud. I do not think that the spots exert any influence on the annual temperature. I register the height of the barometer and thermometer three times in the course of each day, but the annual mean numbers deduced from their observations have not hitherto indicated any appreciable connection between the temperature and the number of the spots. Nor, indeed, would any importance be due to the apparent indication of such a connection in individual cases, unless the results were found to correspond with others derived from many different parts of the earth. If the solar spots exert any slight influence on our atmosphere, my tables would, perhaps, rather tend to show that the years which exhibit a larger number of spots had a smaller number of fine days than those exhibiting few spots.”
These observations seem to show that the spots exert no influence upon the weather, and to be satisfactory. But, perhaps, they are not entirely so. No effect would, of course, be expected from day to day, and perhaps the annual mean may not be seriously disturbed, and yet the spots may seriously affect the seasons. Popular tradition has fixed upon certain periods, of 10, 20, and 40 years, for the return of winters of unusual severity; and the tables of Mr. Webster, and other facts, show that it is not wholly without foundation. If we, and those we have cited, are not mistaken in most of the views expressed, the natural effect of a partial interception or failure of the sun’s rays, by or from the existence of the spots, would be to decrease the exciting power of the solar rays upon terrestrial magnetism, and, as a consequence, the volume of the trades and their amount of moisture. This would increase the mean heat of the summer in the temperate zone—for the less the volume of trade, the less precipitation and variable wind, and succeeding polar waves of cooler air, and the greater mean heat. On the other hand, the same cause, and the feebler heating power of the sun’s rays, would make the winters more severe, both from an absence of a portion of heat, derived directly from the sun’s rays, and a less mitigating influence, from the action of the trade, by reason of its decreased volume. So, too, the absence of spots, and a more powerful influence from the solar rays, may gradually carry the machinery further north in summer, and further south in winter, and thus make the seasons extreme without seriously disturbing the mean of the year. And both these may occur in a more marked degree over our intense magnetic area than in Europe. I am satisfied that they do so occur. That the partial failure of the sun’s rays limits the transit of the machinery, and the volume of the trades during the latter half of the decade, and extends the transit and increases the volume during the first half, producing an occasional severe summer drought and severe winter, in the warmest portion of the decade. And that the variations correspond with the difference in the character and number of the spots in different decades, and hence the longer and shorter periods.
Turning to the tables of Dr. Webster, we find that a general tendency to extreme seasons does seem to exist from the 6th to the 10th year of every decade, and especially of every alternate decade. The periods of 1707-8, 1728, 1737 and 1739, 1749-50, 1758-9, 1779-80, 1798-9, are those in which the tendency was seen most decided. These tables are very general. The thermometer was not perfected till about 1700, and did not get into general use before 1750. There were very few meteorological registers kept, or accessible to Dr. Webster. Hence he was obliged to resort to such other sources of information as were open to him, and such statements as he found are not always entirely reliable. The oldest inhabitant is apt to express himself very strongly respecting present extremes, and fail somewhat in his recollection of those which have past. Still his tables afford general and obvious evidence of the regularity of those periodic conditions.
| A.D. | Summer. | Winter. |
| 1701 | hot and dry | .... |
| 1702 | hot and dry | .... |
| 1703 | .... | .... |
| 1704 | dry Europe | .... |
| 1705 | .... | .... |
| 1706 | hot, dry Europe | .... |
| 1707 | very hot | .... |
| 1708 | .... | very severe |
| 1709 | .... | .... |
| 1710 | .... | .... |
| 1711 | .... | cold Europe |
| 1712 | wet England | .... |
| 1713 | wet England | mild |
| 1714 | dry and hot | .... |
| 1715 | dry | .... |
| 1716 | very dry | severe |
| 1717 | .... | severe |
| 1718 | hot and wet | .... |
| 1719 | .... | cold America |
| 1720 | dry Europe | .... |
| 1721 | .... | .... |
| 1722 | cold, wet | .... |
| 1723 | .... | cold |
| 1724 | wet England | .... |
| 1725 | wet England | .... |
| 1726 | .... | .... |
| 1727 | dry, hot Amer. | .... |
| 1728 | hot Amer. | severe Europe |
| 1729 | .... | .... |
| 1730 | .... | very cold Eng. |
| 1731 | .... | .... |
| 1732 | .... | severe Amer. |
| 1733 | dry Eng. | .... |
| 1734 | .... | .... |
| 1735 | wet | .... |
| 1736 | wet | .... |
| 1737 | .... | very severe Am. |
| 1738 | .... | .... |
| 1739 | wet England | very severe Eng. |
| 1740 | .... | very severe Am. |
| 1741 | .... | .... |
| 1742 | .... | severe Syria |
| 1743 | hot | .... |
| 1744 | .... | .... |
| 1745 | .... | .... |
| 1746 | .... | .... |
| 1747 | hot and dry | severe |
| 1748 | dry | .... |
| 1749 | very dry | .... |
| 1750 | very hot | very severe |
| 1751 | wet England | severe Amer. |
| 1752 | very hot Amer. | .... |
| 1753 | .... | severe |
| 1754 | .... | mild Amer. |
| 1755 | .... | severe Europe |
| 1756 | .... | severe Syria |
| 1757 | .... | .... |
| 1758 | hot | .... |
| 1759 | .... | severe |
| 1760 | .... | .... |
| 1761 | very dry Amer. | .... |
| 1762 | very dry Amer. | severe |
| 1763 | .... | .... |
| 1764 | hot Europe | .... |
| 1765 | hot Europe | severe Europe |
| 1766 | hot and dry Eur. | very severe |
| 1767 | .... | cold |
| 1768 | hot | .... |
| 1769 | hot | .... |
| 1770 | wet England | .... |
| 1771 | wet Am. & England | cold Europe |
| 1772 | hot America | Am., great snow |
| 1773 | .... | .... |
| 1774 | .... | severe Europe |
| 1775 | .... | .... |
| 1776 | hot | severe Europe |
| 1777 | .... | .... |
| 1778 | hot | mild |
| 1779 | hot Eng. | very severe |
| 1780 | .... | .... |
| 1781 | .... | .... |
| 1782 | dry Amer. | .... |
| 1783 | hot | very severe |
| 1784 | hot | .... |
| 1785 | dry Europe | cold |
| 1786 | cool | cold |
| 1787 | cool | .... |
| 1788 | rainy Amer. | cold |
| 1789 | cool spring, hot summer | severe Eur., mild Amer. |
| 1790 | .... | .... |
| 1791 | very hot Am. | cold |
| 1792 | .... | .... |
| 1793 | hot, dry Am. | mild Amer. |
| 1794 | .... | severe Europe |
| 1795 | Amer., hot, rainy | .... |
| 1796 | Autumn very Dry Am. | cold Amer. |
| 1797 | cool Am. | severe Amer. |
| 1798 | very hot} | {long & severe |
| 1799 | very dry Am.} | {Amer. & Eur. |
Still more definite evidence is found in the meteorological tables of Dr. Holyoke and Dr. Hildreth, and an account, by Dr. Hildreth, of the seasons when the Ohio River was closed or obstructed by ice, found in Silliman’s Journal, new series, vol. xiii. p. 238.
Thus, we have, from the tables of Dr. Holyoke, the following annual means, from 1786 to 1825, inclusive. I have arranged them in periods of five years. It will be seen that there are three peculiarities observable. First, a marked difference between the first and second periods of the decade, corresponding, generally, with the presence or absence of the spots. Second, a difference in the mean of the decades which may well be supposed to correspond with the difference in the number or size of the spots since a like difference is observable in number and size, and the time when they reached their maxima and minima, in the table of Schwabe. And, third, there are occasional single cold years during the warm period, and these correspond with what the tables of Dr. Webster show for both the sixteenth and seventeenth centuries. In relation to this, it should be remembered that volcanic action is a frequent and powerful disturber of the regular action of terrestrial magnetism, and that the extremes, for that reason, are frequently meridional or local and alternating; and to that cause very great extremes, and marked exceptions, may be due, notwithstanding the spots upon the sun may exert an influence in producing hot summers and cold winters toward the close of each decade. Thus, to select an instance to illustrate this and explain an anomaly: The coldest season during the whole period, embraced in the following tables, is that of 1812. This occurs during the decrease of spots, and the warm half of the decade. Turning to the table of volcanic action, and of earthquakes, found in the Report of the British Association for 1854, we find that year was remarkable for earthquakes in the United States and South America. In December, 1811, earthquakes commenced in the valley of the Mississippi, Ohio, and Arkansas, felt also at places in Tennessee, Kentucky, Missouri, Indiana, Virginia, North and South Carolina, Georgia, and Florida, though not so severely east of the Alleghanies, which continued until 1813. About the same time they commenced in Caraccas, and, in March, 1812, became severe over the greater portion of the northern section of South America, and in the Atlantic. No such general and continued succession of earthquakes occurred during the other periods embraced in the tables, and the mean of the following five years was very low, embracing the memorable cold summer of 1816.
| Cold Period. | Warm Period. | Cold Period. | Warm Period. |
| 1786 48°.53 | 1791 48°.963 | 1796 48°.678 | 1801 50°.432 |
| 1787 47°.88 | 1792 48°.44 | 1797 48°.135 | 1802 50°.794 |
| 1788 47°.676 | 1793 50°.96 | 1798 49°.471 | 1803 50°.24 |
| 1789 47°.68 | 1794 50°.768 | 1799 48°.291 | 1804 48°.328 |
| 1790 46°.53 | 1795 50°.173 | 1800 49°.989 | 1805 50°.792 |
| Mean of period 47°.659 | Mean 49°.901 | Mean 48°.910 | Mean 50°.117 |
| 1806 47°.982 | 1811 50°.76 | 1816 47°.113 | 1821 48°.15 |
| 1807 48°.132 | 1812 45°.28 | 1817 46°.277 | 1822 49°.81 |
| 1808 49°.485 | 1813 47°.702 | 1818 48°.009 | 1823 47°.58 |
| 1809 47°.92 | 1814 48°.279 | 1819 50°.75 | 1824 49°.25 |
| 1810 49°.001 | 1815 47°.607 | 1820 48°.70 | 1825 50°.99 |
| Mean 48°.505 | Mean 47°.925 | Mean 48°.169 | Mean 49°.15 |
The tables of Dr. Hildreth, from 1826 to 1854, inclusive, furnish, generally, evidence of a like character. There are, however, an anomaly or two which will be observed. From 1826 to 1830, the mean is high during the period when spots were at a maximum. But that maximum embraced a much less number of spots than the two succeeding ones. A contrast appears in the tables of Dr. Hildreth, during the early period, for Dr. Holyoke’s register, for 1827, puts it below the mean, but Dr. Hildreth’s one of the highest of the half century. In 1835 commenced a period when the spots were much more numerous, and from 1835 to 1838, inclusive, the seasons were correspondingly below the mean. From that period to 1844 a gradual and slightly irregular rise took place, excepting the year 1843, when another cold year intervened. The table of earthquakes, published by the British Association, closes with 1842, and I have not access to any others. The occurrence of such cold years, in the warm period, at intervals during the two centuries previous, and in 1812, and onward, and evidently owing to increased volcanic action beneath the western portion of the northern hemisphere, justifies the belief that the low temperature of 1843 was owing to the same cause. The following are the means from the tables of Dr. Hildreth:
| 1826 54°.00 | 1831 50°.87 | 1836 50°.03 | 1841 52°.18 | 1846 53°.64 |
| 1827 54°.92 | 1832 52°.42 | 1837 51°.57 | 1842 52°.83 | 1847 52°.00 |
| 1828 55°.22 | 1833 54°.56 | 1838 50°.62 | 1843 50°.77 | 1848 52°.50 |
| 1829 52°.38 | 1834 52°.40 | 1839 52°.54 | 1844 53°.25 | 1849 52°.09 |
| 1830 54°.93 | 1835 50°.65 | 1840 52°.35 | 1845 52°.73 | 1850 51°.48 |
| Mean 54°.29 | Mean 52°.18 | Mean 51°.52 | Mean 52°.35 | Mean 52°.32 |
The observations of Dr. Holyoke were made at Salem, Massachusetts; those of Dr. Hildreth at Marietta, Ohio.