56 EEPORT — 1872. 



vented the French GoTemment for a long while from giving force to the advice 

 gi'\en hj the French academicians. AVhen these obstacles were partially removed 

 the opportunity was lost for establishing it, and the suggestion quite forgotten. 

 He thinks that the French Government of 1872 wiU take a more intelligent view 

 of the question, especially if the British Association encourages them in doing so, 

 by establishing some definite organization for the purpose, as he is himself a 

 living proof of the interest felt now by the French Government in these matters, 

 having been sent to England in order to report on the late thunder-storms which 

 had been so remarkable. Would it not be in some respects unbecoming of a great 

 nation like England, whose power has been unchecked, to take no interest in 

 these casvialties which are attracting the notice of a foreign people emerging from 

 so many calamities ? 



On a Periodicity in the Frequency of Cyclones in tJie Indian Ocean south of 

 the Equator. By Cblieles Meldeum (Mauritius Observatory). 



"^One of the objects for which the Meteorological Society of Mauritius was esta- 

 blished in 1851, was to obtain extracts from the Meteorological llegisters of vessels 

 visiting the harbour of Port Louis, especially of such vessels as had experienced 

 bad weather in the Indian Ocean. 



Accordingly clerks were employed to copy all the log-books that could be 

 procm-ed. 



In 1853 the system of registration was remodelled. Instead of having the obser- 

 vations contained in each log-book recorded separatelj', all the observations in all 

 the log-books for the same day were entered on the same page. 



As this system has been conducted without interruption to the present time, the 

 Society has now a large collection of observations showing more or less the state 

 of the winds and weather over the frequented parts of the Indian Ocean, in the 

 form of a daily journal, during the last nineteen years; so that a person may find 

 at once what weather prevailed on any day, or in any year, during that period. 



Together with the years 1851-52, therefore, during which the registers were 

 differently kept, we have twentv-one years' continuous obsei-vation from the meridian 

 of Greenwich to 120° E., and from 23° N. to 45° S. 



Adding to the information obtained by the Society throughout these twenty- 

 one years, numerous observations collected by several persons for the previous four 

 years (1847-50), we have a more or less complete record of all, or ver}^ nearlj-^ 

 "all, the cyclones which have taken place in the Southern Indian Ocean during 

 the last twenty-five years; for Mauritius is so much in the track of these cyclones, 

 and so much frequented by vessels in distress, and by others trading between the 

 Colonv and England, India, and Australia, that it is scarcely possible for any -Niolent 

 hurricane to happen without being noticed. 



Taking now, for the present, the area comprised between the equator and the 

 parallel of 25° S., and the meridians of 40° and 110° E., and examining a Table of 

 the cyclones that have occurred there from 1847 to 1872, it is fomul that some 

 years "have been remarkable for a frequency, and others for a comparative absence 

 of cyclones. 



The five years 1847-51 were characterized by cyclone-frequency. Then came 

 a period of comparative calm (1852-57), which was followed by six years (1858- 

 63) remarkable for cyclones. The next five years (1864-68) showed a con.sider- 

 able decrease ; and since 18G9 there has been an increase, until, for the present year 

 (1872), the number of cyclones is already (28th June) greater than in any year 

 since 1861. 



What has now been said is not only borne out by the records of the Meteorological 

 Society, which give detailed accounts of the hurricanes, but also, I have little 

 doubt, by the books of the Docks and Marine Establishments. Especially in 1847 

 and 1848, and again in 1860-63, the harbour of Port Louis was at times crowded 

 with disabled ships ; whereas in the j'ears 1855-57 and 1866-68 there were very few. 



It will be seen that these years correspond pretty closely with the maxima and 

 minima epochs of sun-spots. 



