M. Gautier, of Geneva, and, later, MM. Arago and Barratt, made a series of researches into the tabulated temperature at several stations, and for many successive years. They arrived at the conclusion that, on the whole, the weather is coolest in years of spot-frequency.
But recently the matter has been more closely scrutinized, and it has been found that the effects due to the great solar-spot period, although recognizable, are by no means so obvious as had been anticipated.
These effects may be divided into three classes: those affecting (1) temperature, (2) rainfall, and (3) terrestrial magnetism.
As respects the first, it has been discovered that, when underground temperatures are examined, so that local and temporary causes of change are eliminated, there is a recognizable diminution of temperature in years when spots are most frequent. We owe this discovery to Prof. C. P. Smyth, Astronomer Royal for Scotland. The effect is very slight; indeed, barely recognizable. I have before me, as I write, Prof. Smyth's chart of the quarterly temperatures from 1837 to 1869, at depths of 3, 6, 12, and 24 French feet. Of course, the most remarkable feature, even at the depth of 24 feet, is the alternate rise and fall with the seasons. But it is seen that, while the range of rise and fall remains very nearly constant, the crest and troughs of the waves lie at varying levels. After long and careful scrutiny I find myself compelled to admit that I cannot find the slightest evidence in this of a connection between underground temperatures and the eleven-years period of sun-spots. I turn, therefore, to the chart in which the annual means are given; and, noting in the means at the lesser depths "confusion worse confounded" (this, of course, is no fault of Prof. Smyth's, who here merely records what had actually taken place), I take the temperatures at a depth of 24 French feet. Now, neglecting minor features, I find the waves of temperature thus arranged: They go down to a little more than 46½ degrees of the common thermometer in 1839-'40; rise to about 47¾ degrees in 1847; sink to 47¼ degrees in 1849; mount nearly to 47¾ degrees again in 1852-'53; are at 47 degrees in 1856-'57; are nearly at 48 degrees in 1858-'59; then they touch 47 degrees three times (with short periods of rising between), in 1860, 1864, and 1867; and rise above 47½ degrees in 1869. Now, if we remember that there were maxima of spots in 1837, 1848, 1859-'60, and 1870, while there were minima in 1843, and in 1855-'56, I think it will be found to require a somewhat lively imagination to recognize a very striking association between the underground temperature and the sun's condition with respect to spots. If many spots imply diminution of heat, how does it come that the temperature rises to a maximum in 1859, and again in 1869? if the reverse, how is it that there is a minimum in 1860? I turn, lastly, to the chart in which the sun-spot waves and the temperature-waves are brought into actual comparison, and I find myself utterly unable to recognize the slightest as-
