The Astronomical Register.

No. 178.

OCTOBER.

1877.

DOUBLE-STAR ASTRONOMY.

At the May meeting of the Royal Astronomical Society in 1874 the following remarks were made by the AstronomerRoyal : "Some few years ago there seemed to be in England an excess in the numbers of observers and measurers of double stars, but a reaction seemed to have taken place, and perhaps it had gone too far; there was no lack of instruments in this country with amply sufficient aperture for the work, but now, at all events, they do not seem to be used. Possibly such instruments are employed in wandering after the new objects that present themselves from time to time, but it would be much better if they were devoted to some systematic work of this kind."

Of the truth of these words there can be no doubt, although an examination of the Memoirs alone gives the following list of papers on the subject during the ten years preceding 1874:

1866-" A synopsis of all Sir William Herschel's micrometrical measurements," &c., by Sir John Herschel.

&c.

1867-Dawes' great catalogue.

1870-"Seventh catalogue of double stars observed at Slough,"

And in 1874 appeared the great catalogue of double stars by Sir John Herschel.

If we go

back another ten years we find the following papers:

1854-Powell on the orbit of a Centauri.

1856-Powell's first set of measures at Madras.

1858-Jacob's measures of 120 double stars.

1860-Lord Wrottesley's measures.

1862-Powell's second series of measures at Madras.

During these years numerous papers on double star orbits, methods of computing such orbits, and lists of measures appeared

VOL. XV.

in the pages of the Astronomische Nachrichten and other journals. In spite of all these evidences of activity, however, the words of Sir George Airy correctly represented the state of this branch of astronomy. The widespread enthusiasm created by the Herschels and Struve, and maintained by Dawes and Smyth, had passed away. A reaction had set in. But even while these words were being spoken, several amateur observers in widely separated countries, and unknown to each other, were carrying out schemes which, if completed, will do much to wipe away the reproach. We propose, therefore, to give some of the results of careful enquiry, which seem to justify the statement just made.

At the

We need hardly remind our readers that probably every year some careful measurements of double stars are made at most of the public observatories in Europe and America. Lists of measures of important pairs will be found in the volumes issued from Greenwich, Oxford, Berlin, Königsberg, Washington, Cambridge, Cincinnati, and other observatories. More especially is this true of the observatories at Poulkowa and Lund. former very considerable attention has always been paid to double stars, and it is hoped that ere many months have passed there will be in the hands of astronomers generally two volumes of measures, the results of more than thirty years' work, by the distinguished director, Otto Struve. The first volume will contain all the measures of the most important of 's and H's stars, while the second will give the results of repeated examinations of the pairs discovered by O. S. himself.

At Lund, double stars have received much careful attention, resulting in the publication in 1876 of a fine memoir by Dunér. This work gives the author's measures of a large number of pairs from 1867 to 1876, and is a very valuable contribution to double star astronomy.

At the new physical observatory at Oxford, too, special attention is bestowed on a selected number of binary stars. These are carefully measured, and the orbits of several have been submitted to elaborate investigation.

The double star work of the Cincinnati observatory deserves notice here. In 1875-6 many careful measurements of 166 double and triple stars were made with the 11-inch refractor, and these have lately been published in a separate form. How greatly the separate publication and early liberal distribution of this kind of work by our public observatories would facilitate the labours of computers of double star orbits and others who interest themselves in this branch it is well worth while pointing out in this place.

But the Astronomer-Royal's remarks referred rather to amateur

observers than to the scant attention which can be spared for such work in a public observatory, and therefore to this class of workers we will confine the rest of our remarks.

Beyond all question the most honoured place belongs to Baron Dembowski. This distinguished observer began his noble series of measures in 1855; his most recent list appeared in the Astronomische Nachrichten in January, 1876. Long may he be spared to enrich double star astronomy with results which for excellence are surpassed by none.

Mr. Knott, who has made a series of very fine measures of binary stars, has of late been occupied in collecting them and throwing them into a form suitable for publication in the Memoirs. We trust soon to see them, and also in the future many more measures by this excellent observer.

66

Mr. S. W. Burnham, of Chicago, in 1873, communicated a paper to the Notices of the Royal Astronomical Society, entitled Catalogue of 81 double stars, discovered with a 6-inch AlvanClark refractor." This was the first of a numerous list of papers by this most energetic and successful observer. Possessed of a very fine eye and an excellent 6-inch Alvan Clark refractor, Mr. Burnham has since 1870 discovered and measured nearly 500 new pairs. That these objects, many of which are extremely close and difficult, will yield a considerable number of most interesting systems, there can be no doubt, and it is with great pleasure that we notice the fact that Dembowski has already executed the measurement of many of them. But this is not all. Mr. Burnham has also found time to collect a vast number of measures of double stars, to study the nature of the changes in angle and distance of many, to classify them-in short, to compile a General Catalogue of Double Stars, in which the R.A. and Dec. will be reduced to 1880. This most valuable work will it is hoped be ready for distribution before the end of this year.

Dr. Doberck, of Mr. Cooper's observatory, Collooney, Ireland, has been engaged since 1875 in the study of the orbits of binary stars, and in the actual measurement of such objects. We have no space for the already long list of admirable papers this astronomer has in two years communicated to the Astronomische Nachrichten, the Notices, the Transactions of the Royal Irish Academy, &c.

In 1871, Mr. Wilson and Mr. Seabroke began a series of double star measures with the Temple equatorial, a fine instrument by Alvan Clark, aperture 84 inches. Considering the nature of the daily occupation of these gentlemen, and the fact that the instru ment was intended for the use of the school, work of a systematic character and of general interest was hardly to be expected.

Instead of this, however, a valuable series of micrometrical measurements of double stars and several papers on the orbits of binary stars have already appeared in the Memoirs and Notices. We Te see, too, that a second series of measures will form part of the next volume of the Memoirs.

Mr. Talmage, of Mr. Barclay's observatory, Leyton, has for many years occupied himself much with the measurement of double stars. Three volumes have already issued from this observatory, and we may expect a fourth shortly.

As early as 1869 Mr. Edward Crossley and his assistant, Mr. J. Gledhill, turned their attention to this branch of astronomy. In conjunction with the Rugby Observatory they devised a systematic plan of operations. This included the repeated measurement of all known binary and other important pairs, the formation of a list of binaries, the writing of the history of all the most important objects, and the collection of complete lists of measures. As the years passed on the plan came to include also descriptions of all the equatorials hitherto used in this class of work, a list of all known papers on the subject, and also scme account of the graphical and other methods of obtaining the elements of the orbit of a double star. A list of micrometrical measures of 484 double stars, made at Mr. Crossley's observatory has already appeared. Mr. Wilson and Mr. Gledhill have also lately published "A preliminary list of binary and other interesting double stars." This last list will again appear, we understand, as complete as labour and criticism can make it, under the title, "A working list of binary and other interesting double stars." This list if freely distributed will no doubt be most useful to amateur observers. We understand that the whole of the original plan has been carried out, and that the work will probably be in the printer's hands before the end of the

year.

Lastly, we must notice the unwearied labours of M. Flammarion in this department. This enthusiastic astronomer has collected very extensive lists of measures of a very large number of double and triple stars, has discussed the apparent or real changes with the greatest care, and has now ready for the press, as one result of his industry, a very complete catalogue of such objects with lists measures, remarks, elements of orbits, &c. This work is but the latest of his researches in double star astronomy, and we have lately heard with much pleasure that M. Flammarion has joined the ranks of amateur observers of double stars, one of the instruments of the Paris Observatory having been placed at his service. No doubt the above sketch is far from correctly representing the full activity existing in the department of double star astronomy. No doubt both in England and abroad there are many

observers quietly but earnestly working and collecting results, which will gradually find their way into the transactions of our learned bodies. Enough, it is hoped, has been written to prove that this branch of astronomy has not lost the charms which long years ago fascinated Struve and Smyth.

OPTICAL SPECTROSCOPY

OF THE RED END OF THE SOLAR SPECTRUM AT A HIGH ALTITUDE IN THE SKY.

PART II. THE TRIAL OF CINTRA.

"The Burling Rocks," said the chief officer of the "Aconcagua," pointing to a group of wild cliffs and rocky pinnacles rising apparently out of the depths of the Atlantic, and in fierce combat with both winds and waves; "they are just five hours' steaming from Lisbon." From Lisbon! But squalls of rain soon hid them from our sight, and drove us pell-mell below, to discuss there how to proceed on landing in that desired Lusitanian city, in order to obtain the best solar spectroscopy; for, though we had received confident advice to try the Braganza Hotel therein, it was accompanied with fear of smoke in any large city of the present age of the world.

"There is no smoke in Lisbon," slowly and sententiously remarked a tall Englishman, who had been there already two summers, and was now on his way, with his wife, rejoicing to try it for a third season. Very soon too after that the squalls died away, the rain ceased, the clouds heaved off the scene in one immense canopy, and we were entering the mouth of the mighty Tagus; its fabled golden sands and green-yellow cliffed hills to the south; the serrated range of the dark blue mountains of Cintra far away to the north; and onwards towards the east, the river's northern bank, or rather coast line, so gallantly broad is the noble stream, fringed with palaces and castles, convents now convents no more, and white houses of every degree. The numbers of these continually increased, clustering thicker and thicker the further we proceeded amongst shipping of all nations, and plenty of room for them all and many more too, until at last, white stoned, and seated on more than seven hills, this must be Lisbon which is glittering in light and glory before us. So it was; and who could have admired it more than we did, until, ah! that luckless moment, until examining with rather more critical eyes than our neighbours, and following the wind as it breathed over the city from the north-west, and died away to the southeast,—yes, out there lay the evil thing we had fled from our own