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physical properties. It forms the ridge called Harbour Heights, and reaches from Hut Point (the 

 extremity of the peninsula) to the base of a conspicuous rock some 6 miles along the peninsula named 

 Castle Kock. It forms three quarters of the rock of the peninsula, and rises to an average height of 

 700 feet between the two points mentioned above, and lies nearly perpendicular to the magnetic meridian. 

 It has a specific gravity of 2 929, and under the microscope shows frequent plates of magnetite. Hut 

 Point is entirely formed of it, and it was over this rock that the magnetic observations were made. 



Mount Erebus, 25 miles distant, rises as a full-bodied cone, with its base 12 miles distant. The specific 

 gravity of the external rock may be taken as 2 9. The mountain lies north by east of the Observatory, 

 and is nearly 13,000 feet high. 



Mount Terror, lying nearly 40 miles north-east of the ship, is nearly 11,000 feet high, and is composed 

 of basic rocks of specific gravity 2 -97. The two are joined by a ridge probably 8000 feet high, and of 

 a similar rock to that which forms the masses of Erebus and Terror. 



There is no important land development to the southward, there being only the two islands under 

 3000 feet high and composed chiefly of basalt of specific gravity 2 9. These are respectively 20 and 25 

 miles distant from the Observatory. 



Mount Discovery lies south-west at a distance of 50 miles. It is also conical, with a height of nearly 

 10,000 feet, and the diameter of the base some 10 miles. It appears to be chiefly composed of the same 

 basic rock so common in this locality. 



Turning to the west there is a totally different development of rocks. A great mountain chain, running 

 nearly due north and south, lies at a distance of 70 miles from the ship, and rises to heights of 12,000 and 

 15,000 feet, and is on an average about 11,000 feet high. 



This chain is composed of granites, diabases, and quartzites. The granites form the core of the chain 

 and rise to a height of 4500 feet above sea level. They vary in composition and have a specific gravity 

 between 2-6 and 2-7. Above this occurs a diabase up to a height of 8000 feet. This rock lies practically 

 horizontally on the plutonic rocks (though interrupted by faults) and has a specific gravity of roughly 2'8, 

 while above it, and also horizontal, a sandstone occurs which has a specific gravity not greater than 2 67. 



It must be borne in mind that the above directions of the various land masses are true, and that, as the 

 Declination amounted to about 152 east, the magnetic directions are entirely different, the north-seeking 

 end of the magnet pointing within 30 of the geographical south. 



I am indebted to Mr. H. T. FERRAR, M.A., for the whole of the above geological information. 



Observation Houses. The Observation Houses were constructed of large asbestos slates, screwed on to 

 the outside and inside of a wooden framework. The larger of the two, used for the Variation House, was 

 1 1 6 feet by 1 1 C feet and 6 8 feet high. The Absolute House was slightly smaller. Although, perhaps, 

 small log houses would have been more suitable, they certainly would not have been so light, compact, and 

 easily portable. The asbestos houses were fairly satisfactory, but had some grave disadvantages. 



By the end of February, 1902, the erection of the Variation House (A) was completed, and the 

 variometers set up and working. The Absolute House (B) was completed later, and placed 25 yards to 

 the north of (A). For the absolute instruments a brick pillar was built up through the floor of B, 3 feet 

 (i inches above it, and 2 feet by 1 foot 6 inches square. The door of the house faced nearly due west 

 (true), and narrow openings with sliding doors were made across the roof and down the north and south 

 walls in, as near as possible, the geographical meridian, for the purpose of using a transit instrument or 

 theodolite. 



J.:iniitfh <l[<ii-k. An azimuth peg was erected a little to the south of west, 30 yards from the observational 

 pillar. The peg was an iron one, driven into the frozen ground to a considerable depth, and only 1 foot 

 showing above the surface. At the top was a circular hole, across which a wire was stretched, and a light 

 was placed behind when bearings were taken from the Absolute House in the dark winter months. This 

 mark remained throughout the two years, and was at no time disturbed. The azimuth of this fixed mark 

 fur Declination observations was determined by a number i.f sun aziniuths in Uie spring and summer of 

 1902-1903 and 1903-1904. 



