Oeuvres complètes. Tome V. Correspondance 1664-1665

[p. 172]

N^o 1289.
[R. Hooke] à [R. Boyle].
25 décembre 1664.

La lettre a été publiée dans ‘Boyle's Works, Vol. V.’

December 15. 1664.

Most honoured Sir

This letter¹⁾ coming so late to the posthouse on Tuesday night, was brought back to me, since which I have made farther trial of Monsieur Zulichem's experiment, and both my lord Brouncker, Sir R. Moray and Dr. Wren, were judges and examiners of the experiment, and find, that the trials made with these pendulums, whose balls were of lignum vitae, did not answer to Mr. Zulichem's rule, and therefore it is now much doubted of²⁾. We had yesterday in several parts of England, an account of the appearance of a very great comet³⁾ in the south south-east, with a very long tail, extended towards the north-west; some say about ten yards long, some about two; but how much that is, is difficult to guess, unless we could see it, which I have done all this last night, but to little purpose, by reason of the thickness of the air. It has been seen in Yorkshire, and in Cheshire, and at Portsmouth⁴⁾, and seve-

1) Voir la Lettre N^o. 1288.

2) Dans les ‘Proceedings’ de la séance du 14 décembre 1664 (V. st.) on lit, au sujet de ces expériences, ce qui suit:
The experiment of Monsieur Huygens for the universal measure was repeated twice; and the first time the string of the biggest ball (which was of six inches diameter) was 2 feet 11 ⅘ inches long; and that of the smaller ball was 3 feet 1½ inch long. The president having calculated the proportions, according to Monsieur Huygens's rule, found them vary from it 1/10, the string of the smaller bullet being 1/10 longer than it should be, according to that hypothesis. In the second trial the difference was yet greater, viz. 1/10 or 1/20 or 3/20, which was thought too considerable a difference for a standard.
It was thereupon concluded that there must be either some mistake in the rule, or some fault in the experiment.
The president hinted, that the difference of the air and the bullet might vary the lenght of the line So that a small bullet in a clear air, and a great bullet in a thick air, would cause different measures.

3) Les éléments de cette comète à mouvement rétrograde, qui passa à son périhélie le 4 décembre 1664, ont été calculés par
Halley ‘Astronomiae Cometicae Synopsis’ (Philos. Trans. 1705) et par
L.L. Lindelöf, De Orbita Cometae anni 1664. Helsingforsiae. 1854.

4) Par lord Sandwich, qui se trouvait à bord du vaisseau ‘London.’

[p. 173]

ral other parts of England. I this day got a sight of Master Faithorne's plate⁵⁾, and indeed he has done the face very carefully and well; and, I think, very like; but has not quite finished the plate. The other cuts are finished for your book of Cold⁶⁾; but Master Thompson has again disappointed me. Your anatomical experiments, read by Monsieur Oldenburg⁷⁾, were very highly approved of by the whole Society. I cannot yet perfect my telescope glasses, though they do now very much more flatter me with hopes than at first, so that I shall not yet give over. It seems, by some papers of Monsieur Oldenbourg, that they have made in France object glasses of 250 palms, which is about 160 feet long, and make use of them without a tube⁸⁾.

5) Consultez la Lettre N^o. 1288.

6) New Experiments and Observations touching Cold, or an Experimental History of Cold begun. To which are added, an Examen of Antiperistasis, and an Examen of Mr. Hobbes's Doctrine about Cold. Whereunto is annexed an Account of Freezing brought into the Royal Society by the learned Dr. C. Merret, a Fellow of it. Together with an Appendix containing some promiscuous Experiments and Observations relating to the precedent History of Cold. by the Honorable Robert Boyle. London. Printed for Henry Herringman at the Anchor in Lower Walk of the New Exchange. mdclxv. in-8^o.

7) Dans la séance du 14 décembre 1664 (V. st.).

8) Consultez la Lettre N^o. 1167.