Toronto Astronomical Society
Meeting Minutes - 1869 June 1
Regular Meeting June 1st 1869
Present:- Mr. Winder, the President, in the chair
Meprs Turnbull, Ridgway and Elvins. Two or three visitors were also present.
The minutes of previous meeting were read and confirmed.
Mr. Wm. Thompson, who was proposed at the May meeting was duly elected a member of the Society.
Mr. Turnbull read a lengthy paper, and gave an oral exposition with illustrations on the doctrine of Eclipses in general, and especially on the great eclipse of the sun which will be visible from the City of Toronto, on the afternoon of Saturday 7th August next.
The writer took occasion to notice among other things the fascinating qualities of this department of Astronomy, as it is on this division especially where it gets the character of being above all others one of the exact sciences. In every age, especially since the invention of the telescope, the magnitude, the order and the progressive motions of the celestial bodies have arrested the attention and engrossed the faculties of the most gifted of the sons of men from Pythagoras down to the present Astronomer Royal, Professor Airy. We find every nation or tribe on earth which has made any intellectual mark in the world's progress giving proof that the mind, when free from the cares of busy life, has had an earnest desire to lift higher and still higher that veil which hangs between it and those wonderful sparkling objects scattered so profusely in our nocturnal sky. We find ours is no exception to the onward operation of this law, for if we take for example this speck of space in the Universe which we name the Solar System. Our forefathers could count only about nine primary numbers belonging to it, even including the great luminary of day and that which at times doth regulate the night. Now, in 1869, we can number them by scores upwards of one hundred having been added since Olbers discovered Pallas in 1802.
Now, this passing allusion to the progress of Astronomy in this century suggests the subject more immediately before us this evening, for of all the members of the Solar System, the moon has attracted the greatest notice, her motions have been the most scrupulously scrutinized; she has also been the most refractory, for it is only since the beginning of this century that the practical astronomer has been able to ascertain her motions with the precision attained in the cases of the other planets. The essayist enumerated a number of the causes, and stated as an illustration that to ascertain the place of any of the planets it requires the employment of only five or six equations while to get the moon's true place at an eclipse by the modern tables it is necessary to use at least twelve times that number. Tycho Brahe and Kepler, a German astronomer were the first to register the lunar irregularities for the use of the computer.
This was before the application of the telescope to accurately graduated instruments to find her true place in the heavens.
He then noticed the various tables which have been issued within the last century, for the perfection of our knowledge of the lunar motions, and mentioned in particular Halley's and Flamstead's tables. Then Meyer's which were published in 1753, with about fourteen tabular arguments. Next came Mason's, about the end of last century with twenty two arguments. Then the French Bureau of Longitude issued Burgo's tables with 28 corrections. The next was Burckhardt's and Damaiseau's, and lastly, Carlini's, which bring the arguments from 14 to 79. Carlini's tables include also Hausen's and Airy's two inequalities arising from the action of Venus on the lunar orbit, an addition which shows how closely the Astronomy has sifted the Moon's orbital variations even in her longest cycle of change, and traced htem to their proper source. In the study of the mechanical phenomena of the Moon's motions as resolved by the tables the importance of considering space geometrically or physically was shortly touched upon showing how it was here in a great measure that the mind can grapple with space as a quantity, and examine clearly the positive and negative equations exhibited by the solar and lunar anomalies, and also to keep before the mind's eye the true place and position of the terrestrial and lunar apsides of the two orbits as rendered by the anomalies.
The next part of the subject examined was to find the various elements by the tables, to exhibit the obscuration for Toronto, that is, when the umbra in its transit over the northern hemisphere was at its nearest point to the city and consequently the visible conjunction of the two luminaries.
The several findings as given by the tables which were exhibited in large type may be summed up as follows:-
First contact at Toronto
(Toronto Solar Time)
|4h 48m 30 sec|
|Greatest phase||5h 46m|
|Last Contact||6h 38m|
|Duration||1h 49m 30s.|
|Greatest obscuration||10½ twelvths|
|Diameter of Penumbra||4223 miles|
|Diameter of Umbra||51½ ??|
The centre of totality in its transit over the earth's disc crosses the path which Toronto describes on the 7th Aug next at the exact place where the city is situate at twenty eight minutes past four o'clock in the afternoon. Had the umbra been so far advanced on the earth at this time Toronto would have experienced nearly midnight darkness for the space of about two minutes.
In drawing the subject to a close Mr. Turnbull contrasted the different objects sought in prosecuting the study of Astronomy in our times with those aimed at by the ancients. In early times,
the astronomy was practised only as an art, and the chief object of the art was to know the seasons, to appoint public meetings and to record passing events. This era has passed away, still their motions are as closely watched, but, relative to social affairs, for a different purpose. The great science of Navigation on which both commerce & civilization depend has now, in a great measure its foundation resting upon the accurate observations made of the solar and lunar motions. You are They were aware that along the Moon's path there are at least nine conspicuous sparkling objects that are used for determining longitude at sea. They are named nautical stars, and constitute, as it were, the great hours fixed on our sky dial-plate. They were aware also that as that noble establishment, the Greenwich observatory, whose history in the past has so many attractions to the telesp telescopic observer in every part of the globe. One of the great objects sought at the Observatory is to register the true place of the solar and lunar centres with the above-named stars. All the findings being arranged afterwards in the "Nautical Almanac" department under the superintendence of the highly gifted astronomer Hind, so that "whose head is on the mountain wave and whose home is on the deep" can pilot his vessel with safety, thus contributing directly to give prosperity to Commerce and boundless wealth to our commercial cities. It is here where our noble science gets its peculiar lustre in an intellectual point of view. Indeed, the bearing of this theme in every direction are of a lofty character. To the pious or devout especially, the motions of the two great luminaries he had been trying to scan furnish great consolation. Because the mind is completely emancipated from that mental terror which seized our forefathers on the approach of an obscuration of the solar disc in a clear sky, or of the moon by night.
In fine, to have a clear view of a presiding divine power working by the unerring laws of nature. How it affirmes the soul to join Addison in his beautiful, devotional stanza which permits the fascinating grandeur of our great luminary.
"The unwearied Sun from day to day
Does his Creator's power display,
And publishes to every land,
The work of an Almighty hand.
Moved by Mr. Elvins, seconded by Mr. Ridgway that the thanks of the Society be presented to Mr. Turnbull for his very able and interesting paper.
The members then went out to examine Mr. Turnbull's Reflecting Telescope which he had lately finished. The skill and perseverance of the maker were plainly seen in the workmanship, but the night being unfavourable observations could not be made.
It was decided that the next meeting should be held in the open air in the park, near the ????.