The method of Roy for determining the specific gravity of the blood is a very excellent one, and is capable of yielding sufficiently accurate results. Over thirty bottles containing mixtures of glycerine and water of different specific gravity, ranging from 1·030 to 1·070, are used for the estimation, and a drop of blood to be tested is placed in a sample of one of these fluids. If the drop sinks it is heavier, if it floats it has a lower specific gravity, and then another drop of the same blood is tested until by a few experiments the exact specific gravity is determined.

I published in the Brit. Med. Jour., December 12, 1885, a method invented by me for the easy and yet accurate estimation of uric acid. The method consists in precipitating the uric acid as a silver salt, estimating the silver, and calculating the uric acid from the silver (168 uric acid to 108 silver). As no process was then invented which had itself been tested, except as Salkowski's, by the side of others acknowledged to be inexact, I did all my work with weighed quantities of uric acid, and tested my process—the only straightforward way of working—by adding known quantities of uric acid to one of two samples of a urine, and finding as a result of my estimations of the uric acid in the two samples practically the same difference as the weight of acid added. Hermann confirms my work (Zeitsch. f. physiol. Chemie, Bd. xii. s. 496), and Czapek, working with Professor Huppert, proposes a modification of my method, while Camerer's results (Zeitsch. f. Biologie, Bd. xxvii. s. 113) run on parallel lines. My results have been adversely criticised by Salkowski, who still maintains that uric acid and silver do not combine in a definite ratio. This observer published in 1872 twelve analyses, which show, according to his belief, that there is no constancy in the proportion between the silver and uric acid, and in 1889 he again affirms the same thing, bringing forward in proof of his assertion some dozen analyses made by his colleague Professor Jolin and himself. I was for some time unwilling to take up the controversy where Professor Salkowski had left it, for, certain of the care with which my own work had been done, I was quite willing to let the matter be settled by other and less prejudiced persons, especially as such seemed willing enough to undertake the task. As, however, my method had been widely used, especially for clinical purposes, and as I had frequently to answer queries concerning its accuracy, I felt it my duty carefully to examine once more the whole question, and if there was any doubt about it, at once to set that doubt at rest. I was I confess agreeably surprised to find that Professor Salkowski had made a slight mistake, which when rectified places his own results and mine in complete accord. In order to make this point quite clear I will venture to reproduce Professor Salkowski's results, arranging his analyses in order, beginning with the one having the least uric acid.

The phenomena known as haze, fog, mist, and rain are in a general way but the successive development of the same process, and the line which divides the one from the other is very indefinite. Dust in the atmosphere produces a haze, and the thickness of a haze of this kind depends principally on the amount of dust present when the relative humidity of the atmosphere is very low. But as the humidity increases the effect of the vapour increases also; the dust particles attract the water vapour which becomes deposited on them, thus increasing their size and their hazing effect, till at last when the air is nearly saturated it becomes very thick, and forms what we call a fog; when in this condition, the thickness of the atmosphere depends principally on the degree of saturation. Between the haze and the fog, however, there is no recognised distinction in kind, it is principally one of degree. After the air is saturated and the conditions are such as to tend to cause supersaturation, then a change takes place in the condensation. A few of the dust particles have water deposited on them, and after a time they grow and become little drops of water, in which the original dust nucleus bears a very small proportion to the total weight. At this stage it is still called a fog, but after more water is deposited on the small drops they grow and become what is known as mist, and when the mist drops combine and fall they are called rain-drops.

Dear Professor Tait,-—I write to put on paper an account of the observation I mentioned to you to-night, in case you should think it worth communicating to the Royal Society of Edinburgh.

In the course of last summer I was led, in connection with some questions about lighthouses, to pass a beam of sunlight, condensed by a lens, through the flame of a candle. I noticed that where the cone of rays cut the luminous envelope there were two patches of light brighter than the general flame, which were evidently due to sunlight scattered by matter in the envelope which was in a state of suspension.

The first three pressure-columns of the following little table were constructed from the elaborate data given by Drs Ramsay and Young in their important paper “On Evaporation and Dissociation,” Part IV. (Phil. Mag., May 1887). They give, in metres of mercury, the pressures required to confine one gramme of oxide of ethyl to various specified numbers of cubic centimetres, at temperatures near to that of the critical point.

Since the previous communication to the Society by the author and Professor Prince, not a few dubious points have been cleared up, and, by the courtesy of the Fishery Board for Scotland, further investigations on the general subject carried out at the St Andrews Marine Laboratory. Under the former head may be mentioned the large unknown pelagic egg, with a spacious privitelline space, termed Ovum of Pleuronectid B. This has been proved by Mr E. W. L. Holt to be the egg of the Long Rough Dab, so that the ambiguity which has existed since the Trawling Expeditions of 1884 is now at an end. The larval and early post-larval stages of the species have already been described and figured. A more detailed series of observations have also been made on the development of the Lemon Dab or Lemon “Sole,” as it is somewhat ambiguously termed, showing how readily ova can be transmitted long distances, and the larval and post-larval stages reared subsequently. Formerly, only the ovarian egg of Miiller's Topknot was described and figured; now the fertilized and free-floating egg and its development have been studied. Like the egg of the Turbot and Brill, this has an oil-globule. The larva is tinted of a deep gamboge-yellow on head, trunk, and upper part of yolk-sac, while the oil-globule is conspicuous at the posterior and lower part of the yolk by an environment of the same bright hue.

We have ventured to bring our examination of this specimen under the notice of the Society, not so much for its pathological interest, as for the light which it throws upon the normal mode of growth of the skeleton. There has been a tendency of late to regard endochondral ossification as quite secondary in importance to that of membranous ossification, but we believe that the case illustrates in a very striking manner the important part played by ossification in cartilage in the growth of the greater part of the skeleton.

The author has ascertained the approximate composition of the gases in the blood of certain Invertebrate animals. The apparatus used for this purpose was that of Gautier slightly modified (fig. 1); and the method allows the collection of the blood in vacua (from the time of leaving the vein, &c.) without any alteration in its composition. The glass receiver ACD (left-hand figure), in which the vacuum is made, has a canula E fastened to its lower end. The canula is drawn out into a fine capillary point, which is pushed into the artery, vein, or under the hypodermis, as the case may be. After introducing the canula into the blood system, the tap B is opened and the blood rises into the receiver. The gases are evolved almost immediately, and by means of the pump they are collected over mercury in the tube ab, where their composition is ascertained.

I had wished to render my visit to your country, which has always been in such sympathy with natural science, more interesting by the presence of a new scientific instrument—of a ship constructed entirely for scientific research; but, in spite of the best of wills, I have, after proceeding for several hours on the way to Edinburgh, been obliged to return to the Thames, in order to allow the builders to finish their work, in which they are unfortunately in arrear.

The manner in which the electric resistance of cobalt varies with high temperatures does not seem to have been studied with any great care. The peculiar behaviour of iron and nickel as regards their change of resistance with temperature is now well known With a view to discover if cobalt presented any similar peculiarity, I set Mr Ōmori, one of the physical students in the Imperial University, Japan, to investigate the question. The chief results are embodied in the present short paper.

So far as I know, the only satisfactory determination of the position of the cobalt line on the thermoelectric diagram was made by Professor Tait's students in the Physical Laboratory of Edinburgh University some fifteen years ago. The position of the cobalt line, so found, was given along with the positions of certain alloys in a paper by Professor J. Gordon MacGregor and myself, published in the Transactions of the Royal Society of Edinburgh, vol. xxviii. (1878). The particular specimen of cobalt used in these early experiments was a short rod obtained by electrolytic decomposition. The noteworthy facts regarding its thermoelectric line were that it lay below nickel on the diagram, and that its inclination to the lead line was much greater than the inclinations of the iron and nickel lines.

The following results in magnetic strains are, so far as I am aware, new. They supplement in an interesting way Joule's old result of no change of volume in an iron rod when it is magnetised. What is given here is only preliminary, and suggests many lines of research which I hope to be able to follow out later.

Part II. contains a continuation of former experiments on the twists produced in the magnetic metals when they are under the combined influence of circular and longitudinal magnetisations.

It is established that a cobalt rod of rectangular section twists left-handedly when a current is passed along it in the direction of magnetisation. That is, cobalt behaves like nickel. Iron, on the other hand, twists right-handedly, until very high fields are employed. These results seem to have a close connection with the magnetic changes of length in these metals; for iron expands in moderate fields, while nickel and cobalt contract, the former always, and the latter till high fields are reached.

On the strength of Dumas' famous Recherche sur la Composition de l'Eau, and adopting the great master's own interpretation of his results, all chemists, until lately, agreed in assigning to the atomic weight of oxygen the value O = 16 (H = l ) ; and it is on the strength chiefly of the same experiments that many of us now hold that O = 15·96 is a closer approximation to the truth !

The first announcement of the construction of this important instrument appeared almost paradoxical: a piece of calcareous spar was to be cut in two, the surfaces of the section polished, and then reunited by help of Canada Balsam: and it seemed strange that from such an operation there should have resulted any change in the optical properties of the mass. Even now that the instrument has been in use for some time, the true nature of its performance is often misunderstood ; while no investigation has been made public, the object of which is to enquire into the laws of the action, and into the circumstances which determine the peculiar forms of the parts.

At the very urgent request of the late Dr Sang, who regarded the above paper as one of his chief contributions to science, I brought before the Council of the Society the question of its publication. From the Minute-Book of the Ordinary Meetings, I find that it was read on the 20th February 1837, though it is not mentioned in the published Proceedings of that date. On 21st July 1891 the Council finally resolved that the paper should be printed in the Proceedings “if otherwise found desirable.” The reasons in favour of printing it seem to outweigh those which may, readily enough, be raised against such a course.

In the paper on this subject, printed in the twenty-sixth volume of the Society's Transactions, the general principles only of this extension were explained; since then the subject has lain aside. An accident has drawn attention to the use of this method for determining cube-roots, and particularly in regard to the duplication of the cube. The consideration of this matter has led to the observation of certain relations which deserve to be recorded.