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12--A NEW SOLVENT FOR GOLD.
BY JAMES Moir, D.Sc
This Paper has been published in the Journal of the Chemical Metallurgical and Mining Society of South Africa.
BY PROFESSOR J. C. BEATTIE, D.Sc., F.R.S.E.
Distribution of Magnetic Observatories throughout the world.
There are at the present day between forty and fifty thoroughly equipped, permanent magnetic observatories in the world. Of these all but five are in the Northern Hemisphere. These five are Batavia in the Eastern Archipelago, Mauritius, Melbourne in Australia, Christchurch in New Zealand, and Córdova in South America. In Melbourne, Christchurch, and Mauritius the capital sum required for building and equipment and the current expenses, are provided by the respective local Governments. On the African Mainland itself the only observatory is Dar-es-Salaam in German East Africa, which is at present in course of erection. There are four in Great Britain, four in France, and four more under construction. Japan has six such observatories, and no European country except Turkey, Servia, Bulgaria, and Greece is without its magnetic observatory.
OF CAPE MAGNETIC OBSERVATORY
ATTEMPTS TO REVIVE IT.
A permanent magnetic observatory was established at the Royal Observatory at the Cape in 1841. It continued in existence till 1853, when the building was burnt down, and many of the records lost. Since then, despite many attempts to resuscitate it, no fixed magnetic station has been in being. The British Association has several times moved in the matter. In its report of 1887 a committee appointed by the Association for the purpose of considering the best means of comparing and reducing magnetic observations reported that the establishment of regular magnetic observatories at the Cape of Good Hope and in South America would materially contribute to our knowledge of earth magnetism." (British Association Report, 1887, p. 320). The same resolution was adopted in 1889 (B.A. Report, 1889, p. 50), and again in 1890 (B.A. Report, 1890, p. 173).
In 1891 the same committee reported that they had hopes that their recommendation of the establishment of a magnetic observatory was about to be carried out under the direction of Her Majesty's Astronomer at the Cape, and at the expense of the Admiralty (B.A. Report, 1891, p. 150). The negotiations fell through, however.
After this date the matter was allowed to rest for some time. It was again brought up in 1898 by the International Meteorological Conference (B.A. Report, 1898, p. 762). By this time electric
tramways had been laid down in Cape Town and its suburbs, and the Royal Observatory, which is within a mile of the rails was no longer a suitable place for a permanent magnetic observatory. The Council of the British Association had therefore to make their appeal to the Colonial Government. The Association transmitted the resolution of the International Conference after having considered and approved of it--to the Cape Government through the then High Commissioner, Sir Alfred Milner. The Cape Premier replied that his Government did not regard as practicable the immediate provision of funds for the carrying out of the scheme (B.A. Report, 1899, p. lxxxv.).
3.-PURPOSES SERVED BY
A MAGNETIC OBSERVATORY.
The proper carrying out of the magnetic survey of a country requires the presence of such an observatory. By means of the latter corrections can be made on field observations which have been taken at periods of magnetic disturbance.
Such an observatory is absolutely essential for the determination of the change in the value of the magnetic elements from year to year. The magnetic chart of the seas neighbouring a land can only be correctly made when this change is known.
Observation shows that the secular change of the magnetic elements is not a world-wide progress of the magnetic needle moving regularly in certain directions, but that in addition there are local causes at work in certain regions. In other words, a permanent magnetic station in England is of no help to magnetism in South Africa. In South Africa at present it is impossible to tell what the magnetic state of any part of it will be ten years hence. With the establishment of properly equipped and properly situated observatories in combination with a thorough magnetic survey it will, it is hoped, be possible in a few years' time to tell at least two or three years ahead what will be the value of magnetic elements in and about South Africa.
In this way the safe sailing of the shipping frequenting our shores will be greatly facilitated. Captain Creak says, in his address as President of the Geographical Section of the British Association in 1903, after expressing regret that there was still no permanent station at the Cape : “Of the value of magnetic charts for different epochs, I have much to say, as they are required for purely scientific enquiry as well as for practical uses. It is only by this means we can really compare the enormous changes which take place in the magnetism of the globe as a whole ; they are useful to the miner, but considerably more so to the seaman. Had it not been for the charts compiled from the results of the untiring labours of travellers by land, and observers at sea, in the field of terrestrial magnetism during the last century, not only would Science have been miserably poorer, but it is not too much to say that the modern iron or steel steamship traversing the sea on the darkest night at great speed would have been almost an impossibility ; whereas with their aid the modern navigators can drive their ships at a speed of 26.5 statute miles an hour with comparative confidence, even when neither sun, moon, or stars are appearing.'
4.-SUGGESTED SCHEME FOR PERMANENT MAGNETIC OBSERVATORIES
IN SOUTH AFRICA.
In offering any suggestions for remedying the lack of permanent magnetic observatories in South Africa, several points have to be taken into consideration. In the first place, the size of the region demands that several observatories be founded. Secondly, the position of these must be chosen in such a way that their usefulness will not be destroyed at a later period by the magnetic fields due to the use of electricity for lighting or for locomotion. This latter consideration demands that no observatory be founded within a distance less than 10 miles of any town which may have electric trams within the next fifty years. Two such stations should be established in the Cape Colony, one at Matjesfontein, the other at Lovedale, one at Bloemfontein, one at Bulawayo, and one in Natal, somewhere on the coast. In addition to the magnetic instruments, instruments for the regular record of atmosphere electricity phenomena should be provided.
The cost per station would be about £3,000 ; and each station except Matjesfontein would require an observer capable of taking absolute measurement of the various magnetic elements.
The photographic records might be sent to a central office, just as meteorological records are at present ; there the work of reduction could be carried out. The establishment of observatories is of no value if the observations are not reduced and published as quickly as possible.
Such an arrangement as this would ensure that. An additional advantage of such a central office would be to carry out systematic comparisons with the different instruments of the various observatories, thus ensuring comparability. The advantage of having a number of such observatories spread at different heights over such a large surface would be incalculable ; many of the outstanding problems in magnetism and atmospheric electricity could be attacked in a rational manner.