infall were that, with few exceptions, there is
more rain in years of sun-spot maxima. S. A. Hill found it to be true of
the Indian summer monsoon rains that there seems to be an excess in the
first half of the cycle, after the sun-spot maximum. The winter rains of
northern India, however, show the opposite relation; the minimum
following, or coinciding with, the sun-spot maximum. Particular
attention has been paid to the sun-spot cycle of rainfall in India,
because of the close relation between famines and the summer monsoon
rainfall in that country. Sir Norman Lockyer and Dr W. J. S. Lockyer
have recently studied the variations of rainfall in the region
surrounding the Indian Ocean in the light of solar changes in
temperature. They find that India has two pulses of rainfall, one near
the maximum and the other near the minimum of the sun-spot period. The
famines of the last fifty years have occurred in the intervals between
these two pulses, and these writers believe that if as much had been
known in 1836 as is now known, the probability of famines at all the
subsequent dates might have been foreseen.

Relations between the sun-spot period and various other meteorological
phenomena than temperature, rainfall and tropical cyclones have been
made the subject of numerous investigations, but on the whole the
results are still too uncertain to be of any but a theoretical value.
Some promising conclusions seem, however, to have been reached in regard
to pressure variations, and their control over other climatic elements.

_Bruckner's 35-Year Cycle._--Of more importance than the results thus
far reached for the sun-spot period are those which clearly establish a
somewhat longer period of slight fluctuations or oscillations of
climate, known as the Bruckner cycle, after Professor Bruckner of Bern,
who has made a careful investigation of the whole subject of climatic
changes and finds evidence of a 35-year periodicity in temperature and
rainfall. In a cycle whose average length is 35 years, there comes a
series of years which are somewhat cooler and also more rainy, and then
a series of years which are somewhat warmer and drier. The interval in
some cases is twenty years; in others it is fifty. The _average_
interval between two cool and moist, or warm and dry, periods is about
35 years. The mean amplitude of the temperature fluctuation, based on
large numbers of data, is a little less than 2 deg. The fluctuations in
rainfall