| SUNSPOTS AND WEATHER. |
By Professor ERNEST W. BROWN,
HAVERFORD COLLEGE.
IT is perhaps not far from the truth to say that the most pressing problem, as far as the daily needs of humanity are concerned, consists in finding some method of predicting the weather. Of the great value which a solution would have it is not necessary to say a word. Yet, in spite of many attempts, the chief problem is as yet unsolved. One may go a step further and say that there is at present no indication of any approach to a solution in the work which has hitherto been published. It is possible to forecast the weather with fair accuracy for a day or two in advance, but the methods by which this is done do not appear to have any bearing on the problem of predicting what the weather will be next week, next month or next year. The latter question must be approached in a quite different manner, and it is the object of this article to show the degree of success attained by one attempt to disentangle the wider fluctuations of climate which nearly every region of the earth's surface shows from year to year.
Weather and climate, like all other phenomena of nature, are nothing more than particular cases of the interaction of certain laws. Properly speaking, chance plays no part in their variations. That the motions of the atmosphere can be classed under well-known mechanical principles, there can be little doubt; that the various types of weather and climate are capable of being deduced from those principles with a sufficiently powerful method of analysis is equally certain; but whether such a method has yet been invented or is in process of being discovered at the present time is open to doubt, if we may judge from the very little that has hitherto been done in the direction of deducing the observed phenomena from the laws which govern them. The difficulties presented by this natural and logical process have caused meteorologists to turn to some other method of restoring order out of the chaos. Instead of deducing the phenomena from the general laws, attempts are being made to bridge the chasm which separates them by starting with the observations and trying to find out if some kind of order can be discovered—a support on which it may be possible to continue the bridge towards the opposite bank.
The procedure to be adopted when the latter method is used is sufficiently simple. Large numbers of observations of temperature,
