Herschel, though observing a hundred and ninety years after the earliest discovery of sun spots, seems to have been the first to suspect their periodic character. To establish this as a fact, and to measure the period, was left for our own times and for the indefatigable observer Schwabe. The probable importance of such a period in its relation to terrestrial meteorology was not only clearly pointed out by Herschel, but he even attempted to demonstrate, from such data as were obtainable, the character of this influence.
Perhaps no one thing which this great philosopher has done better exhibits the catholic character of his mind than this research. When the possible connection of solar and terrestrial phenomena occurred to him as a question to be tested, there were no available meteorological records, and he could find but four or five short series of observations, widely separated in time. To an ordinary thinker the task would have seemed hopeless until more data had been collected. But Herschel's fertile mind, though it could
