like Erckmann & Chatrian, work together and publish their results as a single person. Their telescope has an object-glass 13 inches in diameter, expressly constructed for photography, and the same tube carries also an ordinary telescope of 9 inches diameter, which serves as a tender to the other, and enables the operator to keep it accurately pointed during the exposure of the plates. The whole is mounted substantially after the so-called English pattern of equatorial, like the telescope at Greenwich.

At the Astronomical Congress which had been held at Paris in April and May, it was decided to undertake the construction of a photographic chart of the whole heavens by the co-operation of about a dozen different observatories, the apparatus used to be the same everywhere, as well as the plates and processes of development. The Paris instrument was selected as the standard, and many of the other instruments are already well advanced in their construction. It would take us too far to enter into the details of the matter nowbut clearly this photographic mapping of all the stars will be, when accomplished, the greatest astronomical achievement the world has ever seen; transmitting to posterity an accurate

and permanent record of the present state of the heavens, and furnishing a secure foundation for the future structure of stellar astronomy.

Another day we went to Meudon with Lieutenant Winterhalter, to visit "the Observatory of Physical Astronomy." This is also a Government institution, established in 1876 for the new astronomy, as Professor Langley calls it, its main work being spectroscopic research and the study of the physical features of the sun and planets. Its director is M. J. Janssen, who at the solar eclipse of 1868, in India, discovered how to observe the solar prominences by means of the spectroscope. The same discovery was made, as everyone knows, independently and simultaneously by Lockyer, in England. M. Janssen has been on a number of astronomical expeditions-was in Northern Africa to observe the eclipse of 1870, in India again in 1871, and in Japan in 1874, to observe the transit of Venus. 1870 he made his way out of Paris over the German lines in a balloon, but at his station had unfortunately the same bad fortune as Dr. Huggins, who was near him. He is at present the president of the French Academy of Sciences: an elderly man of middle size, with a ruddy countenance and a bright eye, but not in very vigorous health.

In

We were shown about the establishment by M. Stanoiéwitch, professor of physics in the University of Belgrade, who had been for some time studying celestial physics at the Observatory. He was just closing his work there, and took the Russian eclipse on his way home, being one of the very few fortunates who had good weather. He was at Jaroslav, some 150 miles farther east than we. The site of the Meudon Observatory is magnificent. It is on a hill a few miles west of Paris, which overlooks the city and the country beyond, and commands a panorama even finer than that from the Greenwich tower. During the war the ancient château and most of the buildings on the old royal estate of Meudon were burned; but the stables remain, and in them Janssen has erected the extensive apparatus with which he has been making his remarkable spectroscopic researches upon the absorption of light by gases and vapors -the light being made to travel several hundred feet through large iron pipes filled with the gas at a pressure of two or three hundred pounds to the inch. The place looks more like a great blacksmith-shop than it does like our ordinary ideas of a scientific laboratory. There is a maximum of efficiency, but very little prettiness.

The same thing is true of the buildings which shelter the photographic telescopes and apparatus. They are for the most part temporary structures; and some of the telescopes which are most used are not under cover at all, but are mounted on rough stands in the open air. But the photographic work is admirable. We saw some pictures of sunspots which had been enlarged ten or twelve times from the original negative, so that the spot itself was an inch or two in diameter, and yet showing all the minor details of sun-spot structure clearly and sharply. A large, fine building for the permanent observatory is nearly finished, and is to contain an enormous equatorial carrying two telescopes on the same stand. One of the two telescopes is to be 30 inches in diameter, with the object-glass corrected for visual use; the other is to have a photographic object-glass of two feet in diameter.

Janssen, through his personal friendship with Gambetta, was very fortunate in securing liberal government support for his establishment. Admiral Mouchez, at the old Observatory in Paris, seems to have had more difficulty. At any rate, he has so far been quite unable to secure the carrying out of his favorite plan, to remove the old Observatory from its present unfavorable site in the heart of the city, and re-establish it in a better one outside.

From Paris we went to Strassburg and visited the magnificent new observatory which the German Government has established there. Dr. Kobold, the acting-director, showed us through the establishment. A curious and excellent peculiarity of construction is that the central building, which contains the director's residence, library, and computing-rooms, is connected by long underground passages with the two structures which contain the great equatorial and the other instruments. The equatorial has an object-glass nearly 20 inches in diameter, by Merz, of Munich, the largest he has yet made. Its mounting is by Repsold, of Hamburg, and is essentially the same as that of the 15-inch instrument at Pulkowa. The mounting is very elaborate and a little complicated; it certainly is much handsomer and more finely finished than the instruments constructed by the Clarks in this country, and in some respects, especially as regards the illumination of the micrometer and its operation, is unquestionably better; but I very much doubt whether one could work with such an instrument any more accurately, or much more rapidly, than with one of Clark's.

From Strassburg we went to Munich, a city dear to art and science of every kind. To the astronomer its greatest claim to interest lies in the fact that it was the home of Fraunhofer, and for many years, say from 1820 till 1860, the only place where "great and good" telescopes were made. The observatory here, under the Lamonts, father and son, was also for many years one of the most important in Europe. As regards instruments and equipment it has, however, practically stood still for the last thirty

ger.

We visited the optical establishments of Merz, successor to Fraunhofer's successor, and of Steinheil, son of the Steinheil who in 1838 erected and operated, between the observatory and his establishment in the city, the first practically working electric telegraph.

Our way from Munich to Vienna took us by rail through Salzburg, Mozart's old home, to Linz, and thence by boat down the Danube.

At Vienna of course we found abundance to interest and please in art and architecture. We were also especially struck with the resemblance of the Viennese to New Yorkers. In general appearance, in manner of moving, and all externals excepting speech alone, the people of Vienna seemed to me less foreign than those of any other city I was in during the summer. As astronomers, however, our special interest lay in the

on an eminence known as the Türkenschanze, about three miles west of the city. As at Greenwich and Meudon, the observatory commands a noble prospect, with its horizon limited eastward, beyond the city, by the heights of Schönbrunn ; to the south and west, by the Austrian Alps.

The director, Dr. E. Weiss, happened to be out of town, but his lieutenant, Dr. Palisa, the mighty and relentless hunter of asteroids, was at home, and gave us a hearty welcome. He is a man of thirty-five or so, tall, brown, and lank, keen-eyed, quick-witted, and very hard to tire.

We were of course specially interested in the great 27-inch equatorial, the masterpiece of Sir Howard Grubb, the Dublin optician. We found it optically a most satisfactory instrument, distinctly more powerful than the Princeton tele

scope-as naturally it ought to be, having a diameter four inches greater; but mechanically the mounting appeared rather clumsy and inconvenient. We looked through it at a number of more or less familiar objects, and made a somewhat careful study of the beautiful "ringnebula" in Lyra in connection with Dr. Spitaler, the young assistant who is working up the nebula with the instrument. He is also engaged in a very promising attempt to utilize the instrument for photography. The objectglass not having been constructed for this purpose, the ordinary methods of course fail; but by following out the plan suggested by Vogel, of Potsdam, using a sensitive plate treated with eosin, and inserting a yellow glass in front of it, it is found possible to get excellent results from objects sufficiently bright. While we were present Dr. Spitaler made one moon-picture with an exposure of little more than one second.

It is unfortunate that, after building this magnificent observatory, the Austrian Government should be compelled by its financial embarrassments to support it very meagrely; if a small part of the money which was expended on the structure were now available for running expenses, the return of results would be vastly increased.

There is another excellent private observatory at Ottakring, in the suburbs of Vienna, established by and belonging to Herr von Kuffner, but we had not the time to visit it.

From Vienna we turned our course northward toward Berlin through Prague and Dresden. Our day at Prague was a very interesting one; for the place is full of old astronomical associations, as well as of imperial and ecclesiastical memories. There lived the Emperor Rudolph, the enlightened patron of astronomy, and there Tycho Brahe and his pupil Kepler found a refuge from persecution, and did some of their best work. From a strictly scientific standpoint, the Prague observatory does not now amount to much. It is on the roof, and in the garret, so to speak, of the old university building, a hundred feet or more above the ground; and for the most part the instruments are too

VOL. IV.-11

small for making observations of much scientific value. But what most attracts the visitor's attention are two old quadrants of 5 or 6 feet radius, which were actually used by Tycho and Kepler in their observations, and are still in situ, and in good repair; there are other instruments also, such as parallactic rules and astrolabes; and altogether I imagine the whole establishment gives one a better idea of the observatory of mediæval astrological astronomy than anything else existing; except perhaps the old observatory upon the city wall of Peking, where there yet stand a number of still larger and finer instruments of the same ante-telescopic type.

We found ourselves in Berlin on July 31st, sweltering under a temperature of 97° F., a temperature rarely attained in that part of the world. The first of August brought in the rest of our party. We remained in Berlin nearly a week, and of course took occasion to visit both the old national observatory and the new Sonnenwarte at Potsdam. The older institution, of which Encke was so long director, and in which the planet Neptune was first (optically) discovered, in 1846, remains much as it has been for many years, without any considerable additions or alterations. It is the headquarters of the Astronomisches Jahrbuch, and so the centre of a great deal of mathematical astronomy; but as a mere observatory it has rather been left behind, like that at Munich, by more modern establishments; and the building up of the city around it continually, more and more restricts its usefulness. Perhaps the most interesting things in the establishment, if we omit the genial director, Dr. Foerster, and some of his assistants, were the sealed-up clock, which has been running for many years enclosed in an air-tight case, and the new altitude and azimuth instrument by Bamberg. The Sonnenwarte, we found a very interesting place; the building is new and fine, beautifully situated on an eminence that commands a fine view of Potsdam, and of the more remote park and palace of Sans Souci, whose great fountain forms a conspicuous feature of the landscape. Everything at Potsdam was trim and orderly; but not from want of use. Dr. Vogel, the

director, is specially devoted to spectroscopy, and his second in authority, Dr. Loehse, to photography. The veteran Spoerer is there, still keeping up his researches on sun-spots, and there are a number of younger men, some working at photometry, some experimenting upon the earth's density, and others at still different problems-each on his own. While in Berlin we took an opportunity, with Dr. Foerster's introduction, to visit the optical establishment of Bamberg, who, under the direction of Dr. Vogel, is making object-glasses from the new Jena glass. We examined one of his lenses, of about 5 inches diameter. The colorcorrection was certainly remarkably perfect by far the best I have ever seen; but the surfaces were either badly figured, or else (and I suspect this was the case) the glass was not very homogeneous; at any rate the images were far from satisfactory. We have been told also that the new glass is very soft and subject to corrosion.

We left Berlin for St. Petersburg on Friday forenoon, and the next evening were in the Russian capital. Our journey was pleasant; and the cars were very comfortable, especially those of the Russian train which we took on crossing the frontier at Wirballen. These Russian cars were the best we found in Europe-built of iron, arranged much after the plan of our Mann boudoir cars, but with larger compartments and more room for each passenger.

At St. Petersburg we were met at the station by Dr. Hermann Struve, the youngest son of the director, who saw our party safely settled in our hotel, and then took me with him in his carriage to Pulkowa. We reached the observatory a little before ten o'clock, just as the last twilight was fading, and the stars began to shine. A warm greeting from the noble old director and his family, a couple of hours with the great telescope, and then a good night's restwhat more could an astronomer ask for?

The observatory of Pulkowa is on a little hill about 250 feet high and about 10 miles due south of St. Petersburg, connected with the capital by a road perfectly straight and almost level un

til it reaches the base of the observatory hill, around which it winds at an easy grade to reach the summit. The village of Pulkowa itself is a mere hamlet, the houses mostly wooden, the majority of them not much better than huts or cabins; but the observatory and its dependencies is an imposing mass of buildings, covering several acres and containing residences for all the astronomers and employés of the establishment. It shelters between 150 and 200 people, who are under the control of the director in a relation almost patriarchal.

The observatory was founded by the Emperor Nicholas in 1839-and the ukase establishing it decrees in terms that it is always to be kept in the first rank. So far this has unquestionably been done; and at present, not only in material equipment, but as regards the amount and quality of its work, and the ability and fame of its astronomers, it stands second to no other in the world. Its special forte has been stellar astronomy, but of late it is taking up vigorously the subject of astronomical physics; and the researches, spectroscopic and photographic, of Dr. Hasselberg, who is in charge of the newly erected physical laboratory, have been most important and valuable.

The first director of the observatory was Dr. F. G. W. von Struve, who was called from Dorpat to organize and superintend the new establishment. He died in 1864, at the age of seventy-one, and was succeeded by his son, the present director, his "most high excellency" Dr. Otto von Struve. [See p. 97.] He is a tall, erect, vigorous old gentleman, not yet quite seventy years of age, whose kindly heart and courteous manners win the sincere regard of all who come to know him : and he is well known in America, for he has been here twice, once in 1879, when he gave the order for the object-glass of the great telescope which, until a few months ago, was the largest refractor in existence, and again four years later, when he came to test and accept the lens. On this occasion he made a short visit at Princeton; so that it was an old friend, and no stranger, who greeted us at Pulkowa. His younger half-brother, Baron von Struve, has been for several years the Russian minister at Washington