152 METEOHOLOaiCAL PEEIODICITi'. 



wliat at first sight appears to us a most uncertain way. By and 

 by two years of like cliaracter appear, .and we dream of a cycle, 

 and tlie comfort and value that a knowledge of the period, if 

 there be one, would give us. We started this inquiry ages ago, 

 and in the present day we have heard much about meteorological 

 periods, their causes and effects ; and we have learned, theoreti- 

 cally or practically, to take a deep interest in the subject ; and the 

 very difficulty of selecting the true cycle, or perhaps the conveni- 

 ence of having a number to choose from, so long as our facts may be 

 represented, lends a charm to it. 



To the certainty of one cycle and its undoubted cause we 

 have all been accustomed to give our adherence, but the very 

 familiarity with it often makes us fail to see that the cause 

 which rules in the cycle of greatest changes, viz., from 

 summer to winter, must surely be sufficient by its probable 

 variation to produce the minor changes which distinguish one 

 year from another. We know that a slight change in the sun's 

 position in the sky is sufficient to make the difference between 

 winter and summer ; and yet, when one year differs from another, 

 we seldom suspect the grand cause of any variation. We call in 

 theories of heated plains, unusual rains, or winds, to our aid in 

 explaining the phenomena, while, if questioned at another time 

 as to the cause of the heated plains, or the action of interior 

 continents, we should, without question, attribute them to the solar 

 influence. 



Passing, then, from the annual cycle, about which all are 

 agreed, let us consider some of the "Periods " which have been 

 put forward as the results of observation and investigation. 



The shortest is that which for many years pleased meteorolo- 

 gical observers in Tasmania, viz., two years — a wet and a dry one 

 alternately. Such a period does not take long for its discovery, 

 and is exceedingly convenient in many ways, but after some 

 twenty or five-and-twenty years of regular recurrence, during 

 which observers naturally thought it was fully proved and 

 established, a change came, and two wet years appeared together 

 — 1848 and 1849 — and these were /followed by two dry ones. 

 1849, as we shall see, was a memorable year in the climate of 

 jN"ew South Wales and the other Colonies, but here it was memo- 

 rable as the dryest year on record. There it was the turning 

 point in the two years' period ; and Tasmania, like the other 

 Colonies, has since had an uncertain rainfall. 



The next " period " is one of three years, suggested here by 

 my friend, Mr. Tebbutt, in the Herald, 27th February, 1874, 

 and by him traced through all his observations at Windsor for a 

 period of fourteen years. Por these observations, and also for 

 those of Sydney between 1863 and 1875, it agrees remarkably 

 well with the results ; but, in attempting to trace it back through 



