Transactions and proceedings and report of the Philosophical Society of Adelaide, South Australia . uary, while north-west andwest winds are strongest in September and October. Thegraph of the average October winds corresponds most closelywith the actual distribution of the ash. The chief point ofdiscordance is that the extent of the ash deposits to thesouth, towards Flat, etc., is greater than the averageamount of north wind would suggest. The question of the duration of vulcanicity is discussedlater, but if it be fair to assume that the wind circulation wasat that time much as it is at
Transactions and proceedings and report of the Philosophical Society of Adelaide, South Australia . uary, while north-west andwest winds are strongest in September and October. Thegraph of the average October winds corresponds most closelywith the actual distribution of the ash. The chief point ofdiscordance is that the extent of the ash deposits to thesouth, towards Flat, etc., is greater than the averageamount of north wind would suggest. The question of the duration of vulcanicity is discussedlater, but if it be fair to assume that the wind circulation wasat that time much as it is at present, as suggested by thegraph, and if it be further shown that the duration of thevolcanoes life was brief, then the foregoing results the explosive activity took place about the middle ofthe later half of the year. 6. Age of the Eruption. (a) Relation to Victorian Newer Basalt Period.—Beforediscussing the age of the Mount Gambier vulcanicity it is desir-able that its relationship should be established with the greatperiod of eruptive and effusive vulcanicity that occurred in. Fig. 5. •Sketch map showing the area covered by Newer Basaltsin South-western Victoria, and the volcanic localities ofSouth-eastern South Australia. 183 Victoria in late Tertiary times, and which is known as theNewer Basalt Period. The newer basalts, with their associ-ated scoria and cinder cones, tuffs, etc., cover thousands ofsquare miles of Central and South-western Victoria, and ex-tend almost to the South Australian border. The close relation in composition between the materials ofthe Victorian Newer Basalt Period and those of Mount Gam-bier has already been established. The relationship in spaceof the volcanic features of the two States is quite clear fromfig. 5, and strongly suggests that the South Australian fociare outlying centres of the one great area of activity. Professor Skeats/121 in describing the Victorian NewerBasalts, says:— They form the Melbourne and Keilor plai
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectscience, bookyear1878
