METEOROLOGICAL PEEIODICITY. 167 



they will " beat" just in accordance with the conditions existing. 

 For instance, with one o£ the waves of drought we may have the 

 conditions which shift the trade winds and send a comparatively 

 plentiful rainfall ; or we may have a number of forces at work 

 which shall make the nineteen years cycle of one place the thirty 

 years period of another. 



As bearing upon this question, the history of Lake George is 

 instructive, situated as it is in the mountains, with a well-defined 

 catchment area, and no outlet. It forms a sort of natural rain- 

 gauge, and should afford valuable information. I have been at 

 some trouble to learn its history. In the latter part of 1820 it 

 was discovered, and was then a magnificent sheet of water ; but, 

 fine as it appeared, the blacks declared they had seen it dry, and 

 even covered by a forest — tales that looked, at the time, very 

 improbable. The heavy rains of 1821 and 1822 filled it up con- 

 siderably above what had been its level for many years, for it 

 killed a great number of gum-trees round its margin, many of 

 which were two feet in diameter. In 1824 it was twenty miles 

 long, and about eight miles wide ; from 182G the water 

 gradually dried up, and during the drought of 1827, 1828, 1829, 

 its size got rapidly less ; in 1828 it was fifteen miles long. In 

 1832 it was possible to ride over it, and it appears to have been 

 dry, or nearly dry, from Kenny's Point to George's Gap. In 

 1836 it was visited by Sir Thomas Mitchell, and by him described 

 as a grassy meadow like Breadalbane Plains, with dead timber on 

 it. From this time it became a cattle and sheep run, at times 

 having some water in it, which soon dried up. In 1842 and 1843, 

 water accumulated ; but in 1846 and 1847 it got quite dry again, 

 and it was not until the floods of 1852 that any large quantity of 

 water stayed in it. In the drought of 1866 and 1868 the water 

 nearly all disappeared ; but from 1870 it steadily increased, and 

 by August, 1874, it was higher than ever before known, and 

 again killed a number of trees around its margin. The water is 

 now gradually decreasing (1876). It is therefore evident that 

 from 1825 the lake decreased in size, and though sometimes of 

 moderate extent after heavy rains, it soon dried up, and it was 

 not until 1870 that the lake showed such decided signs of in- 

 crease, rising to its maximum in 1874. It is difficult, nay impos- 

 sible, to say in what years the lake filled up before, but judging 

 from the seasons, it is very probable that it began to fill in 1816 

 and 1817, finding its maximum about 1822. Looking back at the 

 droughts which came before these rains, it is most likely the lake 

 was more or less dry from 1790 to 1800, and at that time afforded 

 the experience related by the blacks in 1820 ; but taking only 

 these points which are historical, we have the lake at its maxi- 

 mum in 1824 and in 1874, a period of fifty years. 



On the Hunter Kiver, about West Maitland, in the early 

 days of the settlement, there were evidences of comparatively 

 s 



