88 A DUST-FALL IN THE SOUTH-WEST OF ENGLAND 
organic carbon amounted to 9-89 per cent., and the organic 
nitrogen to 0-16 per cent. This small proportion of 
nitrogen shows that the organic matter is mainly, or entirely, 
of vegetable origin. In sample No. 2 the organic matter 
contained 2-19 per cent, of carbon and 0-16 per eent. of 
nitrogen, the two representing probably between three 
and 4 per cent, of organic constituents, while most of 
the lime was in the form of chalk. 
During the month of November, 1902, a dust-storm 
visited New Zealand which seemed to have its origin west 
of the Blue Mountains in Australia, and after travelling 
some 1,500 miles through the air, 1,200 of which was over 
the water’s surface, some was collected at Invercargill 
in New Zealand. When the dust was examined with a 
inch objective it showed various vegetable cells, apparently 
portions of the feathery pappus of fruits of compositse and 
similar light matter. Some rounded grains of inorganic 
matter were frequent and in some cases large enough 
(0-03 mm. diameter) to depolarise light. They were 
chiefly quartz, but some were apparently augite, and 
other particles of weathered minerals coloured red with 
iron oxides. To these last the colour of the dust in mass 
was -due. There were also in every preparation observed 
several diatoms. In one preparation there was a piece of 
vegetable tissue composed of fine cells. In all these was 
much carbonised matter.® The chemical analysis of this 
dust after drying it in a water bath is thus given — 
Per cent. 
SiOa 53-68 
AI 2 O 3 18-44 
FeaOa 6-54 
CaO 0-95 
MgO 1-52 
K 2 O 2-58 
Na20 1-67 
Loss in ignition . . . . . .14-60 
99-98 
6 See an interesting letter in Nature (vol. Ixviii. p. 223), by Mr. P. 
Marshall. 
