The photographic news

• Bandzählung: 35.1891
• Erscheinungsdatum: 1891
• Sprache: Englisch
• Signatur: F 135
• Vorlage: Hochschule für Grafik und Buchkunst Leipzig
• Digitalisat: Hochschule für Grafik und Buchkunst Leipzig
• Digitalisat: SLUB Dresden
• Rechtehinweis: Public Domain Mark 1.0
• URN: urn:nbn:de:bsz:14-db-id1780948042-189100009
• PURL: http://digital.slub-dresden.de/id1780948042-18910000
• OAI: oai:de:slub-dresden:db:id-1780948042-18910000
• Sammlungen: LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
• Sammlungen: Fotografie
• Strukturtyp: Band

• Digitalisat: SLUB Dresden
• Strukturtyp: Ausgabe

August 28, 1891.] THE PHOTOGRAPHIC NEWS. 607 SUNSPOTS. The following interesting notes are extracted from a letter by Sir Robert Ball, Astronomer-Royal for Ireland, which recently appeared in the Daily Graphic:— First let me say that no extensive or elaborate apparatus is necessary for the simple observations that I am suggest ing : any fairly good telescope will answer for the purpose. I daresay this paper will be read by many who are enjoying their seaside holiday, and the same telescope that is used for observing a yacht race will often be quite sufficient for observing the sun. Of course, the eye must be protected by the interposition of a piece of dark glass, or in some other manner. If a convenient arrangement for this be not at hand, then a sheet of white paper held near the eye piece can be so placed as to receive a picture of the sun, whereupon the interesting features on the surface of the great luminary that are now attracting so much attention will be distinctly visible. At the present time it happens that the sun is diversified with an exceptionally large number of spots ; in fact, it seems that the number and extent of the spots has been largely augmented during the last six months, nor does it yet appear to have reached its maximum. This increase has not been, however, quite uniform. The surface covered by spots in February was in excess of that in January. There was, however, a falling-off in March ; but in both April and May the area covered was about double that in January, while in June the spotted regions were nearly three times as great as at the beginning of the year. Anyone who is desirous of seeing the exact figures may refer to the current number of Nature, where will be found the particulars of an inte resting series of observations made by M. Marchand, at Lyons Observatory, during the first six months of this year. It appears that since the end of March not a single day has passed without a spot having been visible on the sun. There are also indications of activity exhibited by the brilliant solar objects known as faculae. Indeed, the area of the sun’s surface covered by faculae during the first six months of the present year was in excess of the total amount of faculae seen in 1890. These circumstances will naturally lead to an increased amount of attention being devoted to the sun during the autumnal months. The sunspots are well known to be openings through the glowing luminous exterior by which the somewhat darker interior is exposed. The aspect of the spots is constantly changing. This is partly due to the circum stance that the sun is turning round on its axis, so that the objects now visible on that side of the sun which is directed towards us will, in a fortnight, have passed to the other side of the luminary, and will again have returned to the same position from which they were first observed after the lapse of about twenty-five days. Butthisisonthe sup position that the spots last as long as twenty-five days, and such is not always the case. Sometimes a group of spots will only live for a few days; generally, however, they last for a month or two, and in exceptional instances they en dure for a year, or even longer. The rapid changes which these objects undergo become all the more significant when we bear in mind the enormous dimensions that are concerned. There are spots so large that the whole earth would not be too great to pass through the opening which they indicate. By far the most interesting point in connection with sunspots is that of their periodicity. It is now about fifty years since the patient observer, Schwabe, announced his important discovery. He had for forty-three years diligently studied the face of the sun, and recorded the spots which it presented. At first he seems merely to have aimed at patiently obtaining a record of celestial phenomena. He never could have foreseen the interesting result that he was to obtain when his long and patiently accumulated series of observations came to be discussed. They pointed, however, to a dis tinct recurrence of a maximum exhibition of sunspots at every period of about eleven years. These maxima are, however, not a little irregular both as to the time of their occurrences and the amount of the solar disturbance that they indicate. The last sunspot maximum occurred about 1883 ; but this was somewhat later than was ex pected, so that it seems as if we were now again approach ing a sunspot maximum. There is, however, a wide distinction between the predic tions as to the recurrence of sunspots, and the prediction of ordinary astronomical phenomena, such as eclipses or the like. The latter we can foretell with absolute certainty, inasmuch as the causes which produce them are known to us; but with respect to the sunspot cycle of eleven years, all we can say is that we may expect it to continue because it has been observed in the past, but we know not the reason why. It might naturally be expected that changes in the sunspots should affect in some way the power of the sun for radiating heat, and thus influence the weather. He would indeed be rash who asserted that there was no connection of this nature. It is, however, certain that we have not yet, at all events, been able to trace the slight est connection between sunspots and the practical con sideration of weather changes. Many attempts have, however, been made, and some have even gone so far as to search for a relation between sunspots and the price of wheat. It is impossible to trace any reliable connection of this kind, nor have the attempts to identify commercial crises with periods of sunspot maxima proved more suc cessful. If any relation could be ascertained between sunspots and such terrestrial phenomena there would be every possible inducement to discover it. These have been happily suggested by Prof. S. P. Langley (of the Smithsonian Institution) in a passage with which I con clude this letter: — “ Would it be of any practical interest to a merchant in bread stuffs to have private information of a reliable character that crops the world over would be fine in 1888 and fail in 1894 ? The exclusive possession of such know ledge might plainly bring ‘ wealth beyond the dreams of avarice ’ to the user; or, to ascend from the lower ground of personal interest to the higher aims of philanthropy and science, could we predict the harvests, we should be armed with a knowledge that might provide against coming years of famine, and make life distinctly happier and easier to hundreds of millions of toilers on the earth’s surface.” This maybe possible in the future ; but we seem a long way from it as yet. • Wb understand that Messrs. George Houghton & Son’s port able tent studios are meeting with favourable comments in many quarters. One of these has been in use by Messrs. Barrauds for the past few weeks, first during the cricket week at Canterbury, and afterwards at Burlington House in connec tion with the Hygienic Congress there. This tent has been used at both places for taking many hundreds of portraits for composition pictures, illustrative of both events. As an instance of the portability of the apparatus, it may be men tioned that the tent was in use up to four o’clock on Friday at Canterbury, but was in working order in London at noon on Saturday.