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June 18, 1880.] THE PHOTOGRAPHIC NEWS. 289 Uge Ahotographic Mlebs, Eune 18, 1880, PHOTOGRAPHY IN AND OUT OF THE STUDIO. Photography at the Greenwich Observatory—Solar Physics—Photometer or Actinometer. Photography at the Greenwich Observatory.—At the recent visitation a report was presented to the visitors, who consist of the Presidents of the Royal Society and Royal Astrono mical Society, and the astronomers who hold official posi tions at Oxford and Cambridge. In the twenty-one pages of printed matter, we find that photography still holds its own as an aid to the scientific work carried out there. We learn that between May 20, 1879, and May 9, 1880, photo graphs of the sun were taken on 145 days, and that 270 of these have been selected for preservation. The photographs show a complete absence of spots on 64 days of the 145, while in the preceding year there was a similar absence of spots on 121 days out of 150, and, as the Astronomer- Royal remarks, the minimum of sun spot periods appears to have been about the beginning of 1879, as since October last the Outbreak of spots has been very marked. Those who had the privilege of “entree” to the Observatory on the 5th June would also have been able to see that photo graphs of the spectra of spots had been taken on many occasions to enable a comparison to be made between these and the ordinary solar spectrum ; the only fault that could be found being that the old pyrogallic acid developer and wet plate process were employed for obtaining them. The “ new gelatine plates," we are told, were quite unmanage able, owing to their exoessive rapidity. It need scarcely be sail, also, that the photographic registration of the barometer and thermometer and magnetometer are carried ou in the same excellent manner as it was under Mr. Glaisher, and in process of time the photographic curves must yield something which will be of importance. Solar Physics.—In our last issue we drew attention to this subject, and pointed out what a certain Fellow of the Royal Astronomical Society had written regarding it. For the sake of fair play we have consulted the estimates, i which throw light on the other side of the question. We first find that the sum drawn from the Treasury, to commence with, is not a very large one—only £500—and that none of this finds its way into the pockets of the committee except a small amount for the travelling ex penses of two members who live at a distance; the remain der is appropriated to what may be called the literary part of the job, and to the payment of an assistant for making reductions. Now we have a great respect for Lord Lindsay, but, like other folk, we take our own estimate of his opinions. They may be sound, or the reverse, but that there is a doubt as to them is shown by the fact that the committee are on friendly relations with other astronomers who have not thus condemned their labour. For instance,’in the re port of the Astronomer-Royal, already referred to, we find this remark Various spectroscopic and photo graphic results are communicated to the committee on Solar Physics, with whom we are in friendly communi cation.” If the Astronomer-Royal agreed with Lord Lindsay, we can hardly see how he would have acted as he has. Regarding “ F.R.A.S.," the contributor to the quasi- scientific journal, we have but little to say, as he is rather fond of calling names. “ It is all very well to call a spade a spade,” said a friend to us, “ but it is going a little too far to prefix an epithet unparliamentary to it,” and so we say. There seems to be one locality, and two or three men of science, whose very names act very like a red rag to a bull, and the grain of salt has to be a very large one before we can sanction anything but a very small modicum of what he writes when they are brought into it. We greet this sub ject with one remark, which is, that if any considerable number of men of science think there is anything in “ solar physics,” the sum expended will not ruin the nation, and perhaps will be as profitably employed as much of the secret service money annually voted. If there is nothing in the study of the sun, it will soon be found out, and we do not grudge a committee who perform gratuitous labours under a Government department the small amount of prestige which attaches to them for so doing. Photometer or Actinometer.—Pending the advent of the Warnerke actinometer, we have had resort to a method of photometry which has given us very fair ideas of expo sure necessary during a day’s photography. We covered a strip of glass with squares of a varying number of thicknesses of tracing paper, beginning with three, and ending with fifteen or sixteen. Black figures were painted in these squares corresponding to the thickness of paper. We then made a pasteboard tube of some eight inches in length, and about three-quarters of an inch high and wide. About an inch from one end we cut two apertures, through which the strip of glass would slide. When attempting to expose views differently lighted, we held one end to the eye and pointed the other end, carrying the glass, to a point having a medium illumination, and moved the strip till a square was reached, through which the number on the tracing paper could not be read. This we noted, and from comparing this number with that obtained by an open view a very correct estimate was obtained of the exposure necessary to be given. In one case we had a view on the Thames illuminated with bright sunlight to take, and knew that five seconds with a collo dion emulsion was sufficient exposure to give ; whilst another view was a road shaded by tall over-hanging trees, the exposure for which seemed difficult to guess. The photometer, which had previously been “ scaled,” showed that the exposure required was fifty seconds, and this we judged by “taking a sight ” at the shadows in the middle distance. On our return home the estimate arrived at proved correct, and we had a fully-exposed picture. It is needless to say that in many instances the method might prove fallacious, since the light may be much yellower one day than another, and then much must be left to the judgment of the photographer, the very point which a good actinometer should avoid. In all actinometers there will be one drawback, and that is, that although they will measure the general light from the sky, yet they will not show the general brightness of any particular view that has to be taken. Perhaps a Warnerke actinometer might be provided with a lens slightly out of focus, so as to give a general light, and this might be directed towards the part of the view which would require the most exposure. This would confer a boon on many photographers whose judgment is often at fault in regard to this point. It is the usual plan to judge of the exposure by observing the image on the ground glass of the camera, but there is great liability to err, and something even now seems to be wanted to ren der a photometer of absolute use. For printing purposes, of course, there is not the same difficulty, since an expo sure of the actinometer to the same light as the print should give certain results. Who will help us in this matter ? Our own photometer is but a makeshift. Photographs by Lightning.—The correspondent who sends this wonderful account, notes that it comes from America. The Charlottesville Chronicle says:—“We have heretofore published an account of a portrait supposed to have been photo graphed by lightning on a pane of glass in the window of an old farm house in this county. Another instance of the same curious phenomenon has been found in the window of the mansion house on the Mount Eagle farm. The portraits of four persons are plainly discernible ; the faces pre not. 'all on one pane, and the theory is that the partyewerelallldoking through the window during a thunder-storm, when a sudden .flash of lightning, by some mysteriousvrockssc instantaneously fixed their features on the glass. E Bibliotne BEKLi , Krauesuub° 3’