ADDRESS

Delivered by the President, Mr. H. F. Newall, on presenting the Gold Medal of the Society to Sir David Gill, K.C.B., F.R.S.

FOR the second time in the history of our Society, your President is called upon to present the Gold Medal to Sir David Gill. By their award in 1882 the Council desired to recognise the value of his work in determining the solar parallax from observations of Mars in Ascension; and now, after a quarter of a century, they have awarded the Gold Medal to him in recognition of his contributions to the Astronomy of the Southern Hemisphere, and his other astronomical work.

In fulfilling the task which it is my privilege to attempt this afternoon, I would begin by assuring Sir David Gill of the pleasure which it is to us to have him at home again among us with his vigour unabated. We look forward to the prospect of our having his help in our counsels for many years to come.

The terms of the Council's award are wide. They cover the large range of work which Sir David Gill has accomplished during the twenty-eight years of strenuous activity which he has spent in his capacity as His Majesty's Astronomer at the Observatory of the Cape of Good Hope. It would be a difficult matter to decide whether Sir David Gill has contributed to the advance of astronomy in those years more by his own observational work or by the active performance of his administrative duties. Fortunately it is not part of my task to try to disentangle these two aspects of his work.

Broadly speaking, by his personal labours we have such achievements as his two sets of heliometer determinations of the parallaxes of certain southern stars, and his three determinations of the solar parallax. By his administrative activity the Cape Observatory has been equipped entirely anew with modern firstclass instruments; a vast store of astronomical material has been rendered available for the use of astronomers; not only are the last remaining observations of his predecessors reduced and published, but also the observational materials collected in Sir David Gill's régime are reduced and published up to date.

And, as if these duties were not enough to occupy him, Sir David Gill devoted himself to promoting a unified scheme of geodetic survey of South Africa. In his latest utterance about this work in his Presidential Address to the British Association, Sir David Gill speaks of the great African arc on the 30th meridian.

He says of it that it is the dream of his life to see it completed. When I heard these words at Leicester, it seemed to me that they represented Gill's general frame of mind. Whenever he set his hand to any bit of work, it became the dream of his life to see that particular bit of work completed in the most comprehensive way that he could attain. This frame of mind does not always meet with sympathy; it is liable at times to rouse keen opposition. But Gill has seldom failed to infect others with something of his own enthusiasm.

In doing honour to Gill's work, we shall not in the least detract from it if we pay the sincerest tribute to the co-operation which he has been able to elicit from many workers in many lands. We must not forget the devotion of his staff at the Cape Observatory. We must remember the liberal support he has received from the Lords Commissioners of the Admiralty, both for increased instrumental equipment and for increased staff to deal with the expanded scope of the work. We must pay a tribute to the memory of our late Fellow, Frank McClean, whose generous munificence provided the astrophysical department at the observatory. We shall not forget the services rendered by Professor Kapteyn in the Cape Photographie Durchmusterung, nor those of Dr. Elkin and Dr. Auwers in their allotted tasks in the solar parallax work, nor yet those of Sir W. Morris and many other officers in the geodetic work.

Paying tributes in this wise is only a way of recognising Gill's power of inspiring others to take part in advancing the subject which it is the object of our Society to encourage.

History and Traditions at the Cape.-It has been of great interest, in preparing to write this address and in trying to attune myself to the nature of the surroundings in which Sir David Gill has worked, to trace back through the prefaces of early volumes of observations and through the annual reports something of the history and traditions of the Royal Observatory at the Cape of Good Hope. What an enthralling history it would make for us astronomers if it were written by someone who had the power of picturesque presentation.

We should see Fallows, the first astronomer at the Cape (18211831), awaiting for three and a half years the delayed plans of his observatory, and filling up his spare moments by opening a school and teaching the children of neighbouring farmers-his fee for each. lesson a load of earth, which helped to make the foundation of a garden on the rocky hill chosen for the site of the observatory. We should hear of his applying in vain for permission to measure an arc of meridian.

We should read how he struggled on, making the best of his portable instruments, till the observatory buildings were finished and the permanent instruments were installed-seven years after his arrival at the Cape. Then, after a couple of years of vigorous observations, his able assistant Captain Ronald fell sick, and Fallows would have been left alone at the work but for the

assistance which his wife learned to render by taking the circle readings whilst he was engaged with the transit. It was generous official help that he needed, but before it arrived fever had attacked him and he died in the forty-third year of his age. It is a sad story of a brave man struggling to implant new work in a distant land, and it should make us remember the debt of help that we at home owe to those who are working at a distance from headquarters.

Next we should read of Henderson, who went to the Cape in 1832 and worked there assiduously for thirteen months before he uttered that wail of despair about the situation of the observatory on Snake Hill. He describes it as "on the verge of an extensive sandy desert, exposed to the utmost violence of the gales which frequently blow, without the least protection from trees or other objects to shelter from the wind or sun, some miles from markets, shops, or the habitation of persons with whom those belonging to the observatory can associate." It was in such surroundings that Henderson, with the assistance of Lieut. Meadows, achieved those observations which have made his name famous. He took most of his material back to Edinburgh, and year by year he found time, in the midst of his duties as Astronomer Royal for Scotland, to reduce it all. Our Society had the honour of publishing in its early memoirs fifteen contributions from him dealing with his Cape observations, including his memorable determination of the parallax of a Centauri.

Next we should find Maclear (1834-1870) boldly coming out, at heart a true colonist, making roads, harnessing the wind to draw a water-supply, carting earth, planting trees and rows of pine and wattle to form shelter. By exchange and sale and purchase of land he consolidated the observatory property, and succeeded in getting convenient communication with the main road to Cape Town. Of his scientific labours, it is enough to recall his measurement of an arc of meridian, his multitudinous meridian observations, partly reduced under his own régime, and revised and published by his successors Stone and Gill in the form of four Cape Catalogues for the equinoxes 1840, 1850, 1860, and 1865, which deal with a total of 10,766 stars. In his régime, too, two equatorials were added to the equipment, and with these his observations of comets, nebulæ, double stars, and occultations were made. A new transit-circle was

installed.

So, at the end of Sir Thomas Maclear's directorate in 1870, when he withdrew from the observatory to live for the remaining nine years of his life at Mowbray, within a mile of the scene of his former labours, we should see Stone (1870-79) coming out to the Cape to find an established home and an observatory containing a transit-circle the facsimile of that at Greenwich. Stone was at once engrossed in completing two great objects, (i) the preparation of Maclear's meridian observations for press, and (ii) the re-observation of the stars which had been observed by Lacaille more than a century before. He completed the latter undertaking by the formation of the Cape Catalogue for 1880, containing the places of 12,441 southern stars to the seventh magnitude. During his directorate

he passed through the press two Cape Catalogues for 1840 and 1860, based on Maclear's observations made during thirteen years.

This is in briefest outline the history of the observatory at the Cape of Good Hope up to the year 1879, when Stone returned to England to take up his duties as Radcliffe Observer at Oxford. We have seen the traditions forming

(1) The stellar parallax tradition, implanted by Henderson in his studies of a Centauri, and fostered by Maclear.

(2) The geodesy tradition, implanted first in African soil by the Abbé Lacaille, in vain desired by Fallows, and firmly rooted by Maclear.

(3) The tradition of the Cape Catalogue, implanted by Fallows in his first catalogue of 273 stars, fostered by Airy in his reduction of Fallows' last observations, and firmly fixed by Maclear and Stone, in fact, the traditions of general astronomy.

Into all this goodly heritage of history and tradition Sir David Gill entered in 1879; and looking back upon the records of his directorate, we find he has fostered and extended each one of the traditions he found at the Cape, and has implanted as many more as he found.

Thus by the accumulated labours of its Directors the Cape Observatory has grown to be an observatory of the first rank, of which the nation may justly be proud.

Stellar parallax.-First and foremost among the new traditions we must put the heliometer tradition. Gill's masterly use of this instrument has given us those refined determinations of stellar parallax and of solar parallax, those observations of planets and satellites, and triangulations of stars, that are so honourably connected with his name.

Let me first refer to the determinations of stellar parallaxes, one of his most notable contributions to the astronomy of the southern hemisphere. He has made two sets of determinations; the first were made with a 4-inch heliometer. This instrument was

an old friend, for he had used it in Lord Crawford's expedition to Mauritius in 1874, and had also made his observations of Mars with it at Ascension in 1877. Gill knew he could use it effectively in stellar parallax determinations, and he had acquired it from Lord Crawford for this purpose. Just before he left Europe to take up his duties at the Cape, Gill was fortunate enough to find a young and able astronomer eager to join him in the parallax work. He invited him to come to the Cape as soon as he should have finished his studies at Strassburg. Thus it was that Dr. Elkin went out to the Cape in 1881. For more than two years, a guest in Gill's house, he took his share in Gill's labours, and made it a labour of love.

Their programme of parallax observations was an interesting one. First on the list of chosen stars was, of course, a Centauri, Henderson's star, which still retains its place as the nearest star in the whole sky. Altogether nine of the most interesting stars in the southern heavens were included on the observing list, four