. The Nepheline and Associated Alkali Syenites of Eastern Ontario . he potash in the Indian feld-spar is 5 :1, while in the Canadian and Russian occurrences the soda isonly slightly in evcess, and in the separated feldspar is practically thesame. The following are the molecular ratios in the corundum syenites a=:above:— CaO + + I (a) = 1 Analysis II (a) ^ 1 Analysis III (a) = 1 AL03 : SiOo 1 : = Ontario : = Eussia : = Eussia Mr. M. F. Connor, , has also made analyses of the browncorundum and the magnetite which are present in the syenite
. The Nepheline and Associated Alkali Syenites of Eastern Ontario . he potash in the Indian feld-spar is 5 :1, while in the Canadian and Russian occurrences the soda isonly slightly in evcess, and in the separated feldspar is practically thesame. The following are the molecular ratios in the corundum syenites a=:above:— CaO + + I (a) = 1 Analysis II (a) ^ 1 Analysis III (a) = 1 AL03 : SiOo 1 : = Ontario : = Eussia : = Eussia Mr. M. F. Connor, , has also made analyses of the browncorundum and the magnetite which are present in the syenite are given under I and II respectively. The material in both caseswas selected as free as possible from impurities or alteration products. II. SiOj . AljO, (diff.) ..Oxide of iron CaO MgO Silica and silicatesFeAFeOTiO^HjO Sp. Or. (average fourdeterminations.) The occurrence of the corundum in association with absolutely freshand unaltered minerals, in rocks of undoubted igneous origin and. [ADAMS & BARLOW] ALKALI SYENITES OF EASTERN ONTARIO 73 behaviour, at once removes all doubt as to the pyrogonetic origin of tliemineral, showing clearly, that it is one of the first products of the crystal-lization of a magma supersaturated with alumina and very poor inferromagnesian minerals. The chemical analyses, a« given above, arcin remarkably close agreement with the law formulated by Morozewicz,as a result of direct experiments with artificial magmas, not only as tothe conditions essential to the solution of alumina in sucli alumino-sili-cate magmas, but also with regard to the subsequent separation of allexcess of alumina as corundum, as these solidify on cooling. SUMMARY. 1. The nepheline and associated alkali syenites of this districtpresent one of the most extensive developments of these rocks which isknown. They form part of the Pre-Cambrian complex of the CanadianShield, and occur along the border of the
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