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Transactions. 



contains more inclusions than the outer (Plate XXXVI. fig. 2). Owing to 

 the small size of the bubbles, it is difficult to determine whether they are 

 filled with gas or liquid. Olivine (0-2 mm. X 0-2 mm.) is not common. 

 It contains inclusions similar to those in the sodalite, but they are not 

 arranged in lines. Augite (0-4 mm. X 04 mm.) is of a light-violet colour 

 exhibiting pleochroism. Usually the olivine and augite are mantled with 

 aegirine. The olivine is frequently bunched, as also is the augite. Iron- 

 ore grains are present. 



Matrix. — The feldspar is not resolvable. Aegirine occurs in grains, 

 times it is decomposed, leaving a pseudomorph of magnetite. 



At 



Stony Hill is formed of a basalt dyke elliptical in horizontal and wedge- 

 shaped in vertical section. The basalt has been intruded through the 

 glauconitic mudstone formation, which here is of a sandy nature. The 

 joints of the igneous rocks near the contacts are parallel to the plane of 

 cooling, and only about 2 in. apart A band 6 in. thick of the mudstone 

 has been baked to a cream-coloured rock showing feldspar and augite. 

 Thin sections of the basalt may be described thus : — 



Phenocrysts. — Large crystals of labradorite, in places containing inclu- 

 sions of magnetite. There are smaller crystals of olivine and augite. The 

 former is distinctive in that, besides containing a great number of small 

 round grains of magnetite, it shows under crossed nicols a mosaic of 

 colours. 



Groundmass. — The groundmass consists of sharply outlined labradorite 

 laths, augite, olivine, and magnetite grains. 



The baked mudstone, under the microscope, is seen to consist of large 

 idiomorphic crystals of feldspar (orthoclase and andesine) and augite set 

 in a groundmass of well-outlined feldspars of the same composition as the 

 larger ones. 



NOTOPLEISTOCENE DEPOSITS. 



This includes the clays, muds, and gravels deposited after the close of 

 the Notocene. The clay deposits, owing to their wide extent in the low- 

 lands, have not been mapped. For the greater part the clays are mixed 

 with volcanic boulders, which occur either as a band near the base or 

 throughout the bed. At Abbotsford Station 20 ft. of clay ; with a band 

 2 ft. thick of water-worn pebbles 3 ft. from the base, rests unconformably 

 on the glauconitic mudstone. Similar successions occur in a cutting near 

 the Saddle Hill, railway-siding, and in an exposure on the Fernhill Coal 

 Company's railway near the crossing of Waterfall Creek. These clay 

 deposits all occur at a height of from 120 ft. to 160 ft. above sea-level. 



