348

THE OBSERVATORY.

The author having now performed a part of his duty which he could not abandon, although it was unpleasant, now returns to another and an agreeable portion of his work, which will include a description of the College Observatory, at Dunsinc, and of the Botanic Garden at Ball's Bridge; after which will succeed biographical notices of the men of this University who have distinguished themselves in literature and science, with a list of their publications, so far as it may be possible to obtain such information.

SECTION VII.

THE OBSERVATORY.

Having already sketched out the history of Dr. Andrews's bequest to found an Observatory, and endow a Professorship of Astronomy, and of the unhappy and expensive litigations which arose out of that testament, our object now is one of a more agreeable nature, because it will shew the beneficial result of the learned testator's good intentions.

The aforesaid law proceedings not having been got completely rid of until the year 1781, just seven years after the decease of Dr. Andrews, the Provost and Board at last finding the ground safe under their feet in that affair, lost not a moment in looking out for an able Professor to commence with. To this honourable post Dr. Henry Ussher was the first elected (in 1783). The difficulty of obtaining a proper site for their proposed building now presented itself: this occasioned another lapse of five years ere the present most eligible situation was found, adopted, and secured by purchase, soon after which the proposed building was commenced, under the direction of Dr. Ussher, the Professor. Having thus at length succeeded with regard to the situation of this building, and in obtain. ing an able Professor, the next object was to procure instruments in all respects suitable for the important purpose in view. To ensure this object, the Provost and Board commissioned Dr. Ussher to visit

DR. BRINKLEY ELECTED PROFESSOR.

349

London, and give instructions to the celebrated Ramsden for a transit instrument, six feet in length, and other instruments, all without limitations of price. Just previous to Dr. Ussher's visit to London, Ramsden had completed the astronomical circle of five feet in diameter, which is in the Observatory at Palermo. Perceiving the great scientific advantages to be gained by such an instrument, the Professor suggested to the heads of his college, the propriety of possessing such a powerful apparatus. The Provost and Board immediately ordered a circle of ten feet to be made. This was begun by Mr. Ramsden, and laid aside after he had made some progress in it. He then commenced one of nine feet diameter, which he carried on so far as to divide and nearly finish it, when he got dissatisfied with it and laid it aside. He then commenced one of eight feet, (now in the Observatory ;) this he carried on to a very advanced state, when he died, and after some further delay, Mr. Berg, Ramsden's partner, finished it, and it was set up in the observatory A.D. 1808, that is, about 20 years after it had been commenced. Thus, between litigations and Ramsden's procrastinations, 34 years had passed away before even a beginning could be made in the practical observations; for although the transit instrument had been fixed in its place some years ere this time, yet it could not be of great use without the circle; and this instrument Dr. Ussher never saw, for he died (in 1790) about three years after he had given Ramsden the order for its construction.

On the demise of Dr. Ussher, the Provost and Senior Fellows determined to invite (by advertisement) to a public competition, all the astronomers of Europe who might wish to obtain the Professorship.

In 1792, the competition took place, and was extremely well contested by several candidates eminently skilled in astronomy. At the close, however, Dr. Brinkley, of Trinity College, Cambridge, was found to be the best qualified for this office. The governors of the University, therefore, committed the supervision of the building, the instruments, and, in

350

VALUABLE INSTRUMENTS.

short, every thing belonging to the concern, into the hands of their new Professor, and also commissioned him to go to London, and order from Mr. Ramsden other instruments, without any limitation of price. The next object of the Professor, was the arrangement of the place, the completion of the building, and the commodious disposition of the instruments, so as to give each a direction suited to the observations to be made; and he devised a plan which was approved by the governors of the college, who committed to him the management of those parts that required the greatest nicety and attention. And having satisfied himself that they had secured the three great points requisite for the erection of a proper observatory, namely, situation, foundation, and soil, the Professor commenced his architectural operations, which were completed, and some of the instruments fitted in their situations, in 1798.

To our readers who are not acquainted with the localities of the place, it may be useful to mention that the Halls, buildings, or Lecture Rooms hitherto described, are all within the immediate boundary of the college grounds, which, including the park, contain rather more than 25 Irish, or 31 English acres. The soil is alluvial, the surface flat, and its greatest elevation not more than ten feet above the level of the spring tides in the river Liffy, which is about 150 yards distant from the northern wall of the College Park; consequently, had there been space sufficient whereon to have erected an observatory, the locality could not, under any circumstances, be made suitable for the more important objects of astronomical science; as we shall show in the course of our description of the present edifice, the situation of which has certainly been selected with great judgment, and the plan of the building, mode of construction, and arrangement of the instruments, are equally judicious.

This observatory stands upon a moderately ele

a For these two advantages, the college is indebted to the late Dr. Ussher, who was father of the late gallant and distinguished officer, Captain Ussher, R.N. Dr. Brinkley arranged the instruments.

SITUATION OF THE OBSERVATORY.

351

vated piece of table land, called the Hill of Dunsinc, which lies to the north-west of Dublin, (beyond the Phoenix Park,) near Castle-noc, and is four miles from that city, or five and a half from college. At the observatory, the mercury in the thermometer stands at 0.254 lower than it does at the high watermark (spring tides) in the river Liffy; and when the thermometer reaches 52° in Dublin, it marks 59° at the observatory.

The foundation of this structure is imbedded in a solid and immense rock of limestone, which, it is well known, extends for several miles around this spot, where it rises to within about twelve inches of the surface; and it is of so hard a substance, that when required by the farmers for lime or building, it can only be obtained by blasting it with gunpowder; the incumbent and circumjacent soil is composed of common loam and a substance called limestone gravel, which is extremely absorbent.

The horizon here is very extensive, its range is, in fact, without the slightest obstruction on any side, except that to the southward is situated the long range of Wicklow mountains; some summits of which attain an elevation of 2500 feet or more above the marine level. These mountains, however, are at a distance of from ten to fifteen English miles, a space that removes any apprehension with regard to their having an attractive effect on the plumb-line. Besides this, there is the gradual and equal acclivity of the hill on which the building is erected, which seems a sufficient security to it against any more proximate and dangerous local effects of that nature.

Considered also in another point of view, these mountains afford some striking advantages, which we have witnessed, and which the late professor assured the author, was often useful to his operations. This is, that when the clouds are coming up from the south, the observer may see them directed and retained by the mountains; thus leaving the space from thence

a This is now seven miles, because the English standard of land measure has become the standard measure of Ireland.

352

DESCRIPTION OF THE BUILDING.

to the zenith quite serene; whilst to the east and west, where no such attractions intervene, the sky has been obscured by numerous flying clouds.

From east to south-east the sea is visible, at a distance of from ten to twelve miles, a circumstance presenting several advantages, one of which is, the opportunity it affords, by means of the lighthouses at the end of the mole, called "the south wall," and at Kingstown, for making observations on terrestrial refraction, both by night and day.

In particular states of the atmosphere, but more especially preceding the approach of very severe weather, the outline of the mountains in North Wales is distinctly observable, including the whole Snowdonian range; but much more plainly is seen that ridge of hills known as "the Rivals," which stretches away from north-east to south-west beyond the isle of Anglesea, and terminates in the promontory called Braich-y-pwll, which is the northern boundary of Cardigan bay; these hills are nearly 30 leagues from the observatory in a direct line, but the range of "the Snowdon Hills" is still further inland.

The principal front of the observatory looks towards the east, and is composed of a projecting centre and two wings; the centre is surmounted by a dome, which latter is not only ornamental but useful, as we shall see presently. The two principal apartments in the building, devoted to astronomical purposes are, the " Equatorial" and "Meridian" rooms. The first of these contains one of the finest equatorial instruments in Europe.

This room is elevated above the other parts of the building, so far as to command every portion of the visible horizon. To effect this essential object, the dome has been constructed on the moving principle, and in it is an aperture of two feet six inches wide, which opens six inches beyond the zenith; propelled by a lever fixed in the wall: this implement is applied to cogs projecting from the base of the dome, which can be moved round with the greatest ease, and the aperture may be directed to any part of the horizon.