improved Eidograph, a communication which all who know the value of that exceedingly beautiful instrument must admit was worthy of the high approval of our Institution; and I am particular in mentioning this, as it cannot be doubted that the award of this, the first prize given by the Society, must have augured well for its future success, and proved a great encouragement to those who had the labour and toil of originating and organizing it. But passing from this, I may state generally that premiums have been awarded to Mr Whitelaw for his compensation pendulum; to Mr Galbraith, for his papers on the English Arc of the Meridian; to Mr Landale, for his method of conveying low pressure steam to great distances; to Mr Tait, for his method of producing white light from ordinary or artificial light; to Mr Alexander J. Adie, for his experiments on the motion of water in pipes as applied to heating; to Mr Ritchie, for his new method of ventilating public buildings; to Dr Warden, for his application of totally-reflecting prisms to illuminate the open cavities of the body; to Mr Schenck, for his paper on the progress and position of lithography in Scotland; to Mr John Adie, for his dew-point instrument and improved barometer, and for his method of determining the variation of the compass; to Professor Gordon and Mr Hill, for their mechanical arrangement for ascending the great chimney at St Rollox; to Mr M Candlish, for his account of the Ballochmyle viaduct, designed by Mr Miller; to Mr Paterson, for the machinery employed by him in carrying through the tunnel on the Granton railway; to Mr Leslie, for his inclined plane for canals; to Mr Swan, for his instrument for facilitating the determination of the index of refraction; to Mr James Nasmyth, for several ingenious mechanical inventions, including his safety crane ladle for making heavy castings; to Mr Scott Russell, for his reflector of single curvature for canal boats, and for his new parallel motion and brine gauge for marine engines; to Mr Sang, for his essays on life assurance and other subjects; to Mr John Maxton, for his self-acting stopper for winding engines, and his improved long-slide valve for condensing engines; to Mr Ramsay, for his street-sweeping machine; to Mr Wilson, for

his paper on what is required to improve the dwellings of the working-classes, and for his plans of houses erected by him in furtherance of that object; to Mr Gray, for his doubleacting secure lock, and improved Kinnaird grate; to Sir David Brewster, for his notice of a chromatic stereoscope; to Messrs Fox, Henderson, and Co., for their description of an iron roof erected at Liverpool; to Dr George Wilson, for his skeleton crystallographic models; to Mr Stuart, for his paper on water wheels; to Dr Douglas Maclagan, for his analytical account of gutta percha; and to Mr Robert Bryson, for his method of rendering Baily's compensation pendulum free from hygrometric influence.

It is, however, as you are no doubt aware, a difficult task from so great a number and variety of subjects to make a selection; and I shall only add on this subject, that the Keith Medal, which is the highest prize offered by the Society, has been awarded to

Sir John Robison, for his improvements in the construction of taps and dies;

Mr Edward Sang, for his apparatus for cutting surfaces of glass for optical purposes, and his paper on that subject; Professor Fyfe, for his paper on the use of chlorine as an indication of the illuminating power of coal gas;

Mr Erskine, for his improvements in machinery for working coal-pits;

Mr Thomas Stevenson, for his holophotal system of illuminating lighthouses; and to

Mr John Sang, for his platometer.

Besides these communications, many valuable and interesting expositions have been made to the Society, at the request of the Council, by Professor Forbes, Mr Sang, Mr Buchanan, Mr Glover, Mr Grainger, Mr Rose, Dr George Wilson, Professor Piazzi Smyth, Dr Lees, and others.

But I fear I am overtaxing your patience by laying before you so great an array of names and subjects, without at the same time giving somewhat of interest to the enumeration, by explaining the nature of the different communications alluded to, which our time this evening will not admit of, and I shall therefore hasten from what has been done during past

years, to notice very briefly what is the present state of our Society, with a view more particularly to indicate our prospects for the future.

Our list at present numbers 397 members, 17 of whom have been elected during the last session. I have, as usual in such addresses, to notice the losses which the Society has sustained by death or by the removal to other countries of valuable members. The late M. Arago, perpetual secretary of the Institute of France, was elected an honorary member in 1834, shortly after his visit to Edinburgh, on occasion of the meeting of the British Association for the Advancement of Science in that year. The ordinary fellows whose deaths I have to record are, the Earl of Stair, Mr Charles Inglis Anderson, Mr Eagle Henderson, Mr Charles F. Davidson, W.S., Mr Ralph Richardson, Mr John Taylor, the Earl of Wemyss, and the Rev. Dr Gordon, who, in addition to his high attainments in the most important and honourable of all vocations, had devoted considerable attention to the study of mathematics and natural philosophy, and acted as foreign secretary and vice-president of this Society; thus affording a striking and pleasing example of high religious principle and ardent love of physical science united in the same mind. Dr Daniel Wilson, one of our present vice-presidents, has left this country to fill the chair of Professor of Literature in the College of Toronto; and in him we have lost an active and accomplished member, who carries with him the good wishes of a numerous circle of friends.

With reference to the communications made to us during last session, I think I may safely congratulate the Society; not certainly on their number, but what is of more importance, on their quality. The prize-list about to be submitted to you will intimate the premiums to be awarded; but I think it right to remind you that some important communications made during the last session are either unfinished, or are of such a nature as to render them inadmissible in the prize-list. Of these, I may simply recal to your recollection the exposition of the total eclipse of the sun in 1851, which was given by Mr Swan on the first meeting of the session ;—

the communication by Mr Bow on the construction of roofs, which is still unfinished;-Mr Campbell's paper on AntiLunar Tides; and Dr George Wilson's researches on Colour-Blindness, or Chromato-pseudopsis, which he has been requested by the Society to prosecute further, in the belief that his investigations may lead to highly important results.

I have thus, Gentlemen, ventured to lay before you this slight sketch of the past and present history of our Society, in the hope that the recollections and associations connected with the names of men of eminence who have interested themselves in its behalf, many of whom are now no more, may incite the members present to use increased exertions in maintaining in its usefulness an institution which has so completely fulfilled the objects for which it was founded. I also venture to express a hope that what has been said may be the means of inducing those who are not members to co-operate with us in the good work, by intrusting the Society with their communications; and I think, if anything were wanted to guarantee the continued prosperity of our Institution, it would be the countenance of the gentleman (Professor Kelland) whose name I shall this evening have the pleasure of proposing to succeed me as President.

If the remarks I have offered shall have the effect in any measure, however small, of exciting an interest in our institution, I shall conceive that my occupation of your time this evening has not been altogether mis-spent. In conclusion, permit me to express my sense of the high honour you have done me by placing me in this chair, and my thanks for the uniform support and indulgence which I have received at your hands.

Notice of the Time Ball at the Royal Observatory at Edinburgh. By Professor C. PIAZZI SMYTH, F.R.S.E.* (With a Plate.)

After alluding to the praiseworthy exertions of the late astronomical institution, for the purpose of communicating the true time to the public; and to the successive steps since taken by the Government in the furtherance of those views; the author mentioned the time ball as the last addition that had been made.

The principle of this method of publishing the true time, viz., by the sudden dropping of some large and heavy body, was due to Captain (now Admiral) Wauchope, who, about 1829, frequently memorialized the Admiralty on the subject, and was at length rewarded for his trouble by seeing the erection of the signal, so useful to navigators, at the Greenwich Observatory. Within a few years after, so many were the practical advantages found in consequence, similar timesignals were adopted at Portsmouth, Madras, St Helena, and the Mauritius. And Captain Wauchope, himself going out to the Cape Station on duty in 1835, succeeded before long in having a time-ball established at the Observatory there.

The author had had several years' personal experience within 1837 and 1845 with this ball or balls, for several were made, and literally used up, so difficult was it found, with mere simple workmanship, to secure the perfect action, which Mr Field, of the firm of Maudslay and Field, had obtained by the adoption of a cylinder of compressed air to break the force of the ball's descent.

In 1841, when the Edinburgh Observatory was in full astronomical activity, and everything but the machinery of a time-ball possessed, the erection of one was agitated for by Admiral Milne, Captain Basil Hall, Captain Dall, and others, but unfortunately without success. An interesting mark of

* Given at the request of the Council on 12th Dec. 1853. A working model and diagrams were exhibited.