352 V. DOLMAGE. Younger than these, and cutting sediments of known Cre- taceous age outside the district here considered, are many small intrusions forming sills and dikes, which Leach has grouped together into what he calls the Bulkley intrusives. These intru- sions are of two different rock types, acid members of a peculiar composition, being high in soda, low in potash and medium high in silica; and basic members lamprophyric in composition. In hand specimen the acid type has a reddish pink color, and is seen to be composed of a close aggregate of pink tabular feldspar phenocrysts, uniform in size, having an average length of 4 milli- meters evenly distributed in a scant light gray groundmass, sprinkled with small grains of iron oxide. Under the micro- scope the phenocrysts were found to be albite, and their pink color is due to abundant decomposition products, mainly hematite. The groundmass consists of quartz, sericite, orthoclase, chlorite and hematite. The quartz is the most abundant, while the ortho- clase is almost negligible in amount. The hematite forms pseudo- morphs probably after amphibole. This rock occurs only in the western half of the area where it forms the core of the western mountain group called the Star Mountains. It forms an exceedingly irregular mass with nu- merous long tongues or lobes projecting out in three dimensions. It would be difficult to classify it with any of the common types of injected bodies but it seems to fill all the conditions of Pro- fessor Daly’s definition of a chonolith. The basic members of the Bulkley eruptives occur in all parts of the area, usually but not always forming dikes, and have played an important part in the mineralization of the district. They contain such rocks as diabases, kersantites and odenites, diabases being the most common. ECONOMIC GEOLOGY. A considerable amount of mineralization has been produced along the contacts of all the above-described intrusions, and while no large ore bodies have as yet been discovered in the dis- trict, there are many small deposits, some of which are rich in copper, gold and silver. According to their geographical dis-