Page:Transactions NZ Institute Volume 10.djvu/42

18 For some years previous to 1872, the antarctic stream came loaded with huge islands of ice, to an extent not witnessed by mariners since the route round Cape Horn became so frequented a highway as it has been since the gold discoveries.

Navigation in those seas was for a time so extremely perilous that insurance companies became alarmed, and many shipmasters sent their vessels to struggle back against the westerly winds by the Cape of Good Hope. Another great separation of bergs from their parent glaciers, an occurrence which has no doubt gone on intermittently in all ages, happened in 1829, as related by Sir Charles Lyell. Then, as in these late years, many bergs retained the dimensions of islands when they had reached the longitude of the Cape of Good Hope; some had nearly circumnavigated the globe before they foundered in Australian seas, and one was still many miles in length when seen off Cape Leuwin. An excellent opportunity was afforded for the conveyance of seeds of the same plants if any are produced or remain possessed of vitality in the soil of the lands from which they came, to different places in their route, a possibility dwelt upon by Mr. Darwin, in alluding to the sprinkling of the same flora in far distant regions; it seems probable that had the climate been suitable, plants now unknown there might have by this means been brought far up into Australia when the land was lower, as there is evidence of bergs having been drifted up in former times high into Spencer's Gulf, on the shores of which large boulders of foreign rocks have been left by them. There are no data as yet upon which to found a theory as to the periodicity of these occurrences, which might connect the action of the main-spring which sets the machinery in motion, with any of the many causes, magnetic, sidereal, etc., which have been proposed as influencing alternating cycles of dry and wet seasons—such as the return of Biela's comet every six and a half years—the time of the solar spots every eleven—the twelve-year cycle supposed to have to do with the long one of the revolution of the planet Jupiter, etc., etc. However this may be, there is every reason for believing that when polar winds are more than usually chilled over certain oceanic areas, they will blow with more force, and mingling with other aerial currents nearer to the tropics than in ordinary seasons, condense their moisture.

Australian climates would be the principal ones affected by such a cause, so we find that after the great ice-stream alluded to, the following years were wet ones in the then occupied part of New South Wales. Again, in 1869, commenced a cycle of splendid seasons for the farmers all over the Australias, dry plains were converted into lakes, and steamers ascended the tributaries of the Murray more than 1,500 miles. The consequences of the ice-stream were also felt in New Zealand. In