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I. INTRODUCTORY STATEMENT. 



BY 



L. C. BERNACCHI, F.R.G.S. 



Winter Quarters. The Winter Quarters of the ship " Discovery," of the National Antarctic Expedition, 

 were situated in latitude 77 50' 50" south, longitude 166 44' 45" east of Greenwich, and to the south of 

 a narrow peninsula extending in a south-west direction from the base of an island formed by Mounts 

 Erebus and Terror. The "Discovery" remained frozen-up in her Winter Quarters from February, 1902, 

 until February, 1904. With the exception of the first and last months the magnetic observations extended 

 over the whole period. 



Instruments. Besides the Fox and Lloyd-Creak instruments for the determination of Inclination and 

 Total Force at sea, the " Discovery " was supplied with Unifilar Magnetometers and Dover Circles for the 

 determination of absolute Declination, Horizontal Force, and Inclination on shore, and with a set of 

 Eschenhagen variometers, or self-recording instruments, for obtaining a continuous photographic record of 

 the changes in Declination, Horizontal Force, and Vertical Force. 



The Magnetic Observatory at Christchurch, New Zealand, was made the primary base station of the 

 Expedition in the Southern Hemisphere ; there the constants for the instruments were determined before 

 sailing in 1901, and again on returning in 1904. Our thanks are due to the New Zealand Government 

 for their courtesy in placing the Observatory at our disposal, and to Dr. COLERIDGE FARR, D.Sc., and 

 Mr. H. F. SKEY, B.Sc., of the Observatory, for their valuable assistance. 



As the magnetic programme of the Expedition was an important one, preparations were at once made to 

 commence observational work and to complete the construction of the Magnetic Houses for March 1. 



Observatory Site. The spot selected for the Observatory, although the best available, was hardly an ideal 

 one for magnetic observations. From a magnetic point of view, an observatory of this kind should bo 

 placed in a position as little as possible disturbed by the presence of magnetic rocks ; but it would be 

 difficult, if not impossible, in the whole length of Victoria Land to find such an undisturbed locality, unless 

 it were on the surface and near the seaward edge of one of the extensive ice-floes, far from the actual coast 

 line, such as the Great Ice Barrier. 



The site selected for the houses was a low and fairly level piece of rocky ground close to the extremity 

 of the peninsula, and at a distance of about 300 yards from the ship. (See Plates 15, 16.) 



The peninsula (vide Map) is about 10 miles long by a mile broad, and has an average height of 600 to 

 700 feet, although the extremity where the Observatories were placed was only 30 feet above mean sea 

 level. The rocks of which it is composed are practically of three varieties. 



Geological Formation. (1) A yellow breccia which occurs in three well-marked heights, the nearest of 

 which was 3 miles distant from the Observatory and 1400 feet high. This rock did not appear to be 

 developed to any great extent, but occurred as a volcanic pipe surrounded by the basalt which forms the. 

 major part of the peninsula. 



(2) The trachyte found on Observation Hill, a hill three quarters of a mile distant from the Observatory, 

 and 750 feet in height. This hill was conical in shape, the upper half being composed of a trachyte of a 

 specific gravity 2 244, and the lower half of a lava containing lapilli of a very varying composition, and 

 with a specific gravity in one case of 2 87. 



(3) A black basalt which is by far the most important rock both as regards its development and 



S 



