- 
22 A. C. D. CROMMELIN, ‘ESQ., D.SC., F.B.A.S., ON 
That public sense may try the cause, 
And tell us by what wondrous laws, 
We may be sure, in any year, 
That Comets come which don’t appear. 
For tho’ philosophers may sing, 
That calculation proves the thing, 
Pray, let them tell us how they show 
That this, their calculation’s true. 
At the very time when these scornful words were being 
written in England, the well-known French astronomers, 
Clairaut and Lalande, were so convinced of the truth of Halley’s 
prediction, that they undertook, and with the help of Madame 
Lepaute, successfully carried out the computation of the 
planetary perturbations for the two revolutions of the comet,,. 
1607-1682, and 1682-1759. It was necessary to compute the 
earlier revolution to find the actual angular velocity of the 
comet in 1682, and the later one, in order to find how much 
that velocity was modified by planetary action during the 
ensuing round. Their result was successful, considering that 
the masses of Jupiter and Saturn were still imperfectly known, 
and that Uranus and Neptune were undiscovered. The date 
they assigned was just a month too late, the comet being found 
by the amateur astronomer Palitsch, on Christmas day, 1758, 
and passing its nearest point to the sun on March 13th, 1759. 
After the discovery the Gentleman's Magazine executed a 
remarkable volte-face, and forgot its earlier attitude. In its 
issue for May, 1759, it published these verses, which are dated 
New York, April 16th, 1759 :— 
Hah! There it flames, the long-expected star, 
And darts its awful glories from afar ! 
Punctual at length the traveller appears, 
From its long journey of near fourscore year's. 
Lo! the reputed messenger of fate, 
Array’d in glorious but tremendous state, 
Moves on majestic o’er the heavenly plane, 
And shakes forth sparkles from its fiery train. 
Ah! my misfortune that I live retired, 
And nought avail me arts I once acquired ? 
Here, like a hermit, in my lonely cell, 
Far from the mansions where the muses dwell. 
I’m forced to act the common gazer’s part, 
Alas! unfurnished with the aids of art. 
O for the tube, with philosophic eye, 
To trace the shining wanderer through the sky ! 
