Great Astronomers - Robert Stawell Ball (the little red hen ebook .TXT) 📗

Upper Sackville Street, Dublin.]

 

The next event in the history of the Observatory was the issue of

Letters Patent (32 Geo. III., A.D 1792), in which it is recited

that “We grant and ordain that there shall be forever hereafter a

Professor of Astronomy, on the foundation of Dr. Andrews, to be

called and known by the name of the Royal Astronomer of Ireland.”

The letters prescribe the various duties of the astronomer and

the mode of his election. They lay down regulations as to the

conduct of the astronomical work, and as to the choice of an

assistant. They direct that the Provost and the Senior Fellows

shall make a thorough inspection of the observatory once every

year in June or July; and this duty was first undertaken on the

5th of July, 1792. It may be noted that the date on which the

celebration of the tercentenary of the University was held happens

to coincide with the centenary of the first visitation of the

observatory. The visitors on the first occasion were A. Murray,

Matthew Young, George Hall, and John Barrett. They record that

they find the buildings, books and instruments in good condition;

but the chief feature in this report, as well as in many which

followed it, related to a circumstance to which we have not yet

referred.

 

In the original equipment of the observatory, Ussher, with the

natural ambition of a founder, desired to place in it a telescope

of more magnificent proportions than could be found anywhere else.

The Board gave a spirited support to this enterprise, and

negotiations were entered into with the most eminent instrument-maker of those days. This was Jesse Ramsden (1735-1800), famous

as the improver of the sextant, as the constructor of the great

theodolite used by General Roy in the English Survey, and as the

inventor of the dividing engine for graduating astronomical

instruments. Ramsden had built for Sir George Schuckburgh the

largest and most perfect equatorial ever attempted. He

had constructed mural quadrants for Padua and Verona, which

elicited the wonder of astronomers when Dr. Maskelyne declared he

could detect no error in their graduation so large as two seconds

and a half. But Ramsden maintained that even better results would

be obtained by superseding the entire quadrant by the circle. He

obtained the means of testing this prediction when he completed a

superb circle for Palermo of five feet diameter. Finding his

anticipations were realised, he desired to apply the same

principles on a still grander scale. Ramsden was in this mood

when he met with Dr. Ussher. The enthusiasm of the astronomer and

the instrument-maker communicated itself to the Board, and a

tremendous circle, to be ten feet in diameter, was forthwith

projected.

 

Projected, but never carried out. After Ramsden had to some

extent completed a 10-foot circle, he found such difficulties that

he tried a 9-foot, and this again he discarded for an 8-foot,

which was ultimately accomplished, though not entirely by himself.

Notwithstanding the contraction from the vast proportions

originally designed, the completed instrument must still be

regarded as a colossal piece of astronomical workmanship. Even

at this day I do not know that any other observatory can show a

circle eight feet in diameter graduated all round.

 

I think it is Professor Piazzi Smith who tells us how grateful he

was to find a large telescope he had ordered finished by the

opticians on the very day they had promised it. The day was

perfectly correct; it was only the year that was wrong. A

somewhat remarkable experience in this direction is chronicled by

the early reports of the visitors to Dunsink Observatory. I

cannot find the date on which the great circle was ordered from

Ramsden, but it is fixed with sufficient precision by an allusion

in Ussher’s paper to the Royal Irish Academy, which shows that by

the 13th June, 1785, the order had been given, but that the

abandonment of the 10-foot scale had not then been contemplated.

It was reasonable that the board should allow Ramsden ample time

for the completion of a work at once so elaborate and so novel.

It could not have been finished in a year, nor would there have

been much reason for complaint if the maker had found he

required two or even three years more.

 

Seven years gone, and still no telescope, was the condition in

which the Board found matters at their first visitation in 1792.

They had, however, assurances from Ramsden that the instrument

would be completed within the year; but, alas for such promises,

another seven years rolled on, and in 1799 the place for the great

circle was still vacant at Dunsink. Ramsden had fallen into bad

health, and the Board considerately directed that “inquiries

should be made.” Next year there was still no progress, so the

Board were roused to threaten Ramsden with a suit at law; but

the menace was never executed, for the malady of the great

optician grew worse, and he died that year.

 

Affairs had now assumed a critical aspect, for the college had

advanced much money to Ramsden during these fifteen years, and the

instrument was still unfinished. An appeal was made by the

Provost to Dr. Maskelyne, the Astronomer Royal of England, for his

advice and kindly offices in this emergency. Maskelyne responds—

in terms calculated to allay the anxiety of the Bursar—“Mr.

Ramsden has left property behind him, and the College can be in no

danger of losing both their money and the instrument.” The

business of Ramsden was then undertaken by Berge, who proceeded to

finish the circle quite as deliberately as his predecessor. After

four years Berge promised the instrument in the following August,

but it did not come. Two years later (1806) the professor

complains that he can get no answer from Berge. In 1807, it is

stated that Berge will send the telescope in a month. He did not;

but in the next year (1808), about twenty-three years after the

great circle was ordered, it was erected at Dunsink, where it is

still to be seen.

 

The following circumstances have been authenticated by the

signatures of Provosts, Proctors, Bursars, and other College

dignitaries:—In 1793 the Board ordered two of the clocks at the

observatory to be sent to Mr. Crosthwaite for repairs. Seven

years later, in 1800, Mr. Crosthwaite was asked if the clocks

were ready. This impatience was clearly unreasonable, for even in

four more years, 1804, we find the two clocks were still in hand.

Two years later, in 1806, the Board determined to take vigorous

action by asking the Bursar to call upon Crosthwaite. This

evidently produced some effect, for in the following year, 1807,

the Professor had no doubt that the clocks would be speedily

returned. After eight years more, in 1815, one of the clocks was

still being repaired, and so it was in 1816, which is the last

record we have of these interesting timepieces. Astronomers are,

however, accustomed to deal with such stupendous periods in their

calculations, that even the time taken to repair a clock seems

but small in comparison.

 

The long tenure of the chair of Astronomy by Brinkley is

divided into two nearly equal periods by the year in which

the great circle was erected. Brinkley was eighteen years

waiting for his telescope, and he had eighteen years more in

which to use it. During the first of these periods Brinkley

devoted himself to mathematical research; during the latter he

became a celebrated astronomer. Brinkley’s mathematical labours

procured for their author some reputation as a mathematician.

They appear to be works of considerable mathematical elegance, but

not indicating any great power of original thought. Perhaps it

has been prejudicial to Brinkley’s fame in this direction, that he

was immediately followed in his chair by so mighty a genius as

William Rowan Hamilton.

 

After the great circle had been at last erected, Brinkley was able

to begin his astronomical work in earnest. Nor was there much

time to lose. He was already forty-five years old, a year older

than was Herschel when he commenced his immortal career at Slough.

Stimulated by the consciousness of having the command of an

instrument of unique perfection, Brinkley loftily attempted the

very highest class of astronomical research. He resolved to

measure anew with his own eye and with his own hand the constants

of aberration and of nutation. He also strove to solve that great

problem of the universe, the discovery of the distance of a fixed

star.

 

These were noble problems, and they were nobly attacked. But to

appraise with justice this work of Brinkley, done seventy years

ago, we must not apply to it the same criterion as we would think

right to apply to similar work were it done now. We do not any

longer use Brinkley’s constant of aberration, nor do we now think

that Brinkley’s determinations of the star distances were

reliable. But, nevertheless, his investigations exercised a

marked influence on the progress of science; they stimulated the

study of the principles on which exact measurements were to be

conducted.

 

Brinkley had another profession in addition to that of an

astronomer. He was a divine. When a man endeavours to pursue two

distinct occupations concurrently, it will be equally easy to

explain why his career should be successful, or why it should be

the reverse. If he succeeds, he will, of course, exemplify the

wisdom of having two strings to his bow. Should he fail, it is,

of course, because he has attempted to sit on two stools at once.

In Brinkley’s case, his two professions must be likened to the two

strings rather than to the two stools. It is true that his

practical experience of his clerical life was very slender. He

had made no attempt to combine the routine of a parish with his

labours in the observatory. Nor do we associate a special

eminence in any department of religious work with his name. If,

however, we are to measure Brinkley’s merits as a divine by the

ecclesiastical preferment which he received, his services to

theology must have rivalled his services to astronomy. Having

been raised step by step in the Church, he was at last appointed

to the See of Cloyne, in 1826, as the successor of Bishop

Berkeley.

 

Now, though it was permissible for the Archdeacon to be also the

Andrews Professor, yet when the Archdeacon became a Bishop, it was

understood that he should transfer his residence from the

observatory to the palace. The chair of Astronomy accordingly

became vacant. Brinkley’s subsequent career seems to have been

devoted entirely to ecclesiastical matters, and for the last ten

years of his life he did not contribute a paper to any scientific

society. Arago, after a characteristic lament that Brinkley

should have forsaken the pursuit of science for the temporal and

spiritual attractions of a bishopric, pays a tribute to the

conscientiousness of the quondam astronomer, who would not even

allow a telescope to be brought into the palace lest his mind

should be distracted from his sacred duties.

 

The good bishop died on the 13th September, 1835. He was buried

in the chapel of Trinity College, and a fine monument to his

memory is a familiar object at the foot of the noble old staircase

of the library. The best memorial of Brinkley is his admirable

book on the “Elements of Plane Astronomy.” It passed through many

editions in his lifetime, and even at the present day the same

work, revised first by Dr. Luby, and more recently by the Rev. Dr.

Stubbs and Dr. Brunnow, has a large and well-merited circulation.

 

JOHN HERSCHEL.

 

This illustrious son of an illustrious father was born at Slough,

near Windsor, on the 7th March, 1792. He was the only child of

Sir William Herschel, who had married somewhat late