nd pass through the press, and it is a Fellows to decide whether the Monthly ed through the press that without doubt the hands of Fellows the day before the ether we shall endeavour to exercise so e Monthly Notices through the press as cy of their contents. There has been a eeting, and Easter has occurred during ore a delay has taken place in printing gain the number is a thick one, as you has taken a considerable time to read e Fellows' attention to the point that not be read through, but when they are comsed, the Monthly Notices have to be read Secretaries. It is certainly done so far I believe also with all other secretaries, he Monthly Notices is done at once, withrned by the following day's post, it can than a day without passing over some the hands of the Fellows whether the hurried through the press, so that errors or whether we shall continue to get them in the best manner.

said that the explanations which Mr. ven had been the periodical explanations years at tolerably regular intervals, and that they were at all satisfactory to the Great care should be taken, and he taken, in the preparation of the Monthly d it would be a lesser evil to leave out d least important papers, and get the delay their publication.

Captain Noble said that when Mr. Proctor edited the Notices they were out something like a week before the meeting.

The President said he felt great interest in the Monthly Notices and their punctual appearance, and he regretted very much that they did not appear as regularly as some of the Fellows seemed to think they ought to do. He had been editor of the Monthly Notices for a short time, and it would hardly be believed the difficulty which he experienced in getting the proofs returned from the different authors, so as to be able to get them in proper order for publication. Not only that, but there are times in the year, as at the present, when such a festival as Easter occurs, when there is a holiday week, and then some delay must necessarily take place. When he received his copy of the Monthly Notices on the previous evening he thought it was a marvellous thing that it should appear so soon, considering that it contained 80 pages, and was full of very important papers. Those accustomed to reading proof-sheets containing tabular matter would know that they could not be got through in a short time. They required careful reading, unless they were to be published full of errors. As, however, Mr. Knobel had said, it rested entirely in the hands of the Fellows. If Fellows were desirous that the Monthly Notices should appear punctually, then of course they must be got out, and the Secretaries would do all they could to make them appear before the meeting, but then it might be at the expense of accuracy.

Colonel Tupman said he should like very much to hear from Captain Noble what difference it made to him whether the Monthly Notices arrived before the meeting or not.

Captain Noble said it made this difference, that very often subjects arose at one meeting having reference to papers read at the preceding meeting, and any one who was not present at that meeting would not know anything about the matter under discussion.

Professor Adams hoped the Council or the editors would never be so ill-judged as to send out the Monthly Notices without taking the very greatest care to ensure accuracy. The speedy appearance in print was a matter of much less importance.

Mr. Ranyard said he was aware there was difficulty about the printing of the Monthly Notices, especially with their present printers. He thought there were two ways in which hurry might be avoided. Either papers which were long, or ought to be illustrated, might be postponed at the discretion of the secretaries, or the Monthly Notices themselves might be postponed until after the meeting. It seemed to him that it would be a lesser evil if the longer papers were postponed, and if those which were easily

got through were printed in time for the meeting, and in the hands of the Fellows two or three days before.

The subject then dropped.

Colonel Tupman said that 63 presents had been received since the last meeting, amongst those calling for special notice was a beautiful series of photographs of the Orion Nebula, taken by Mr. Common, who, he hoped, at a later period in the evening, would explain them himself.

The thanks of the Society were returned to the respective donors.

Mr. Green was called upon to exhibit a drawing of Saturn. He stated that he thought it would be interesting at this time in regard to the question of the supposed changes upon the planet's surface. Certain appearances had been reported here, and from America, and from France, which indicated that a change had taken place recently upon the surface of the planet. The period of opposition had now passed and there would be no equally good opportunity for some years of observing the planet with the ring in the same position. The drawing he showed had been made with an 18-inch speculum, with powers varying from 250 to 400. He had taken advantage of all the evenings that had been favourable, but could not say that very good drawings had resulted; and it had been difficult to observe details on Saturn. In past years he had considered that Saturn was a very favourable object to look at with a telescope, in consequence of the general sharpness of the detail, it always bore a higher power than was possible in observing Jupiter; but during the last opposition he was not able to get such good definition, and began to suspect his own sight or the instrument; but on turning the instrument upon Jupiter, lying lower towards the horizon, he was able to see all he desired, and the details came out beautifully. The opposition for 1883 was a finer one for drawing purposes, Saturn then bore a power of 400, all the details could be seen charmingly, and some of the markings appeared more prominently than during the last opposition. Mr. Green had not been able to observe Encke's division in the outer ring, although he had some favourable opportunities for observation during the recent, as well as during the preceding, opposition. He was disposed to think that the appearance which had been described was due to inequalities of tint in different parts of the outer ring, which when seen with a smaller aperture might give the appearance of a division. Many drawings also showed a sharp line of demarcation between the inner ring and the crape ring; but to him it had always appeared that the crape ring merged gradually into the brighter ring outside it. He had at

no time seen a bright spot at the southern pole of the planet, such as was shown in some drawings; and there was but little detail visible from the polar cap to within a short distance of the first dark belt. The markings on the ball of the planet, which were shown in his drawings, had been verified by Mr. Edward Nelson, who observed with the 18-inch reflector, and Mr. Arthur Cottam had confirmed the appearances of the outer ring by observations at Watford.

Mr. Ranyard said he concurred with Mr. Green as to the gradual merging of the crape ring into the brighter ring outside it. The dark belt, as shown in Mr. Green's drawing, was somewhat broader, and lower down towards the equatorial regions than it appeared to him, and he thought that the polar cloud cap was more uniform in tint than it appeared in Mr. Green's drawing. The edge of the dark belt appeared to him not to be uniform, but he could not say that he saw the crenilations drawn by Mr. Green.

Mr. Knobel said there had evidently been a great change in some of the appearances since last February twelve months.

Captain Noble said it might be interesting to possessors of moderate optical means to know that he had seen the northern dark belt quite distinctly with a 4-inch aperture, as against Mr. Green's 18-inches. Many other things which Mr. Green saw he could also see with his smaller telescope.

The President: If no other gentleman wishes to make any remark we will return thanks to Mr. Green. I am sure you will do so, as he has gone into his subject, in a remarkable and most interesting manner, and he has given us, and myself particularly, a great deal of instruction as regards the planet at the present time.

We are privileged this evening, in having amongst us one of our distinguished associates, Professor Langley. We all know Professor Langley, as the Director of one of the most important observatories in America, the Allegheny Observatory. He has done most important work there, and I think he will allow us to ask him to tell us to-night something of the work he has been engaged upon.

Professor Langley: Mr. President, I did not anticipate this honour you have done me to-night in asking me to speak, and I am quite unprepared to make any formal presentation of the work of the observatory you have so kindly alluded to. I can only say, that for the last five years, we have been increasingly engaged in studies connected with the solar energy, regarded, not merely as light, but as heat, and in connection with that we have been investigating the obstacles which our atmosphere offers to the

It is some five years ago

transmission of those radiations. we began to study more particularly those regions of the solar infra red spectrum, which lie beyond the portions which Captain Abney has so successfully photographed, and we had carried our observations to a point which, I think, had hardly been reached by others, when we found the difficulties of the atmosphere prevented us from going much further with our then means. Those means consisted largely of such instruments as the thermopile, the most delicate we then possessed, and we were occupied for a considerable time in perfecting an apparatus more sensitive and perhaps more accurate, with which to carry those investigations further. After many years' study with the pile, we seemed to have reached the limits of its capacity. Now we have an instrument which I have called the bolometer, and which consists of an extremely fine wire, in which an electric current passes, and on which, the heat falling, causes a change in the conductivity, and a consequent deflection in the galvanometer. We commenced mapping the spectrum in the infra red, using for that purpose a grating which should give us a spectrum on the wave length scale, the prism-as is well known-giving us a spectrum which differs with every instrument employed. We know of the excellent work which the prism does, and is doing, but for the point immediately in hand the grating seems to be preferable. The heat, however, in the grating spectrum is in certain portions about 4th of what it is in like portions of the prismatic one, and an instrument of corresponding delicacy was required to measure in the infra red, so that the possession of the bolometer has opened a quite new field to us. Another object we had in view was to find what obstacle our atmosphere opposed to the radiation of the solar and lunar energy, and that of other celestial bodies, and that could best be done, as it seemed to us, by studying the spectrum in portions so narrow that they might be treated as individual rays, which this instrument consisting of a platinum wire, in some cases less than one-thousandth of an inch in diameter, in others, of a platinum tape less thanʊʊ of an inch-was well able to do. Without detaining you with a longer account of the preliminary work on the apparatus (for it was extremely tedious in its preparation) I may say this, it gave us finally an instrument which could measure amounts of heat in such excessively narrow spaces as the separate Fraumhofer lines, and make such explorations in the spectrum as gave us promise of ascertaining more about the effect of the atmosphere than had been done before. In the course of these investigations there was fitted out from the Observatory, at the cost of a citizen of Pittsburgh, and with the