614 



SCIENCE. 



[N. S. Vol. XVIII. No. 463. 



Observatory. He showed that the number 

 of wrecks which came into the harbor of 

 the Mauritius and the number of cyclones 

 observed in the Indian Ocean could en- 

 able any one to determine the number of 

 spots that were on the sun about the time. 

 The Mauritius is most admirably suited for 

 the making of these observations, because 

 the Tropics are really the right region in 

 which to try and estimate the possibilities 

 of this solar action. Meldrum found, in 

 fact, that the maximum number of cyclones 

 was associated with the maximum number 

 of sun spots. He wrote:* 



During the period 1847-72 it is found that 

 some years have been remarkable for a frequency, 

 and others for a comparative absence of cyclones. 

 1847-51 were characterized by cyclone frequency. 

 1852-57 were characterized by comparative calm. 

 1858-63 were characterized by cyclone frequency. 

 1864-68 were characterized by decrease. 

 1868-72 were characterized by great increase. 



It will be seen that the years correspond with 

 the maxima and minima epochs of sun spots. It 

 appears to me that there is more than a mere 

 coincidence as to time. 



The numbers of wrecks during these periods 

 also show a similarly regulated frequency. 



Poey, investigating shortly afterwards 

 the cyclone condition in the West Indies,! 

 found that the greater number of years of 

 maxima of storms fall from six months to 

 two years, at the most, after the years of 

 maxima of solar spots. 



Out of twelve maxima of storms, ten 

 coincide with maxima periods of spots. 

 Out of five minima of storms, five coincide 

 with minima of spots. 



It will be seen that the results from both 

 the Bast and West Indies are the same. 

 Next came the question of a rainfall cycle 

 corresponding to the solar spots.J 



When I was preparing to go to India, 

 in 1871, to observe the eclipse, Mr. Fer- 

 guson, the editor of the Ceylon Observer, 



■' Tiature, Vol. VI., p. 357, 1872. 



t Comptes Rendus, November 24, 1873, p. 1222. 



t' Solar Physios' (Lockyer, 1874), p. 425. 



who happened to be in London, informed 

 me that evcrj'body in Ceylon recognized a 

 cycle of about thirteen years or so, in the 

 intensity of the monsoon— that the rainfall 

 and cloudy weather were more intense every 

 thirteen years or so. This, of course, set 

 one, interested in solar matters, thinking, 

 and I said to him : ' ' But are you sure the 

 cycle recurs every thirteen years, are you 

 sure it is not every eleven years?" adding, 

 as my reason, that the sun spot period was 

 one of eleven, years or thereabouts, and that 

 in the regular weather of the Tropics, if 

 anywhere, this should come out. 



It afterwards turned out that the period 

 in Ceylon was really of eleven years, five 

 or six years dry, and five or six years wet, 

 and that a longer period of about thirty- 

 three years was recognized. 



Mr. Meldrum passed from cyclones to 

 rainfall by a very obvious step, because 

 cyclones are generally accompanied by tor- 

 rential rains. A study of the rainfalls of 

 Port Louis, Brisbane and Adelaide led him 

 to the conclusion that a case had been made 

 out for a supposed periodicity. 



On my return from India I looked up 

 the Cape and Madras records for the 

 periods available, and found that they fol- 

 lowed suit, hence I quite agreed with Dr. 

 Meldrum that investigations were desirable, 

 and I wrote as follows:* 



Surely in meteorology, as in astronomy, the 

 thing to hunt down is a cycle, and if that is not 

 to be foimd in the temperate zone, then go to 

 frigid zones, or the torrid zones and look for it, 

 and if found, then above all things, and in what- 

 ever manner, lay hold of, study it, record it, and 

 see what it means. If there is no cycle, then 

 despair for a time if you will, but yet plant 

 firmly your science on a physical basis, as Dr. 

 Balfour Stewart long ago suggested, before, to the 

 infinite detriment of English science, he left the 

 Meteorological Observatory at Kew; and having 

 got such a basis as this, wait for results. In 

 the absence of these methods, statements of what 

 is happening to a blackened bulb in vacuo, or its 



*' Solar ■ Physics, pp. 424-5. 



