VOL. IX.] PHILOSOPHICAL TRANSACTIONS. 135 



Extract of M. Hmj gens' s Letter, touching his Thoughts on Mr. Hook's Observations 

 for proving the Motion of the Earth, noticed in N° 101 of these Tracts. 



N° 105, p. go. 



The observations of Mr. Hook for finding out the motion of the earth 



are very good, and of great consequence ; but they must be continued, to see 

 whether in the course of one or more years the parallaxes regularly answer to 

 the annual motion of the earth. To which we also shall contribute our labours; 

 and the vault in our observatory, being 28 fathoms deep, will in time be very 

 useful for that purpose. This, if it succeed, will prove an almost entire con- 

 viction of the anti-copernicans, since there will remain for them nothing but 

 this ungrounded subterfuge, to say, that the centre of the sphere of the fixed 

 stars continually changes its place for an annual motion. 



Extract of another Letter from Sig. Cassini, relating to the same Subject. 

 N° 105, p. 90. Translated from the Latin. 



Mr. Hook could not, in my opinion, in a better method investigate the 

 parallaxes of the annual orbit in the fixed stars; nor select for that purpose a 

 fitter star, on account of its lustre, its proximity to the vertex, and not far 

 from the pole of the zodiac. Nor will his endeavour be useless, though it 

 should turn out different from what is required by the parallax. — Indeed our 

 observations could not hitherto show any thing of this kind distinctly, although 

 in the meridian altitudes of the fixed stars, at various times of the year, we 

 should have detected other differences, than those which follow from the pre- 

 cession of the equinoxes for advancing the stars. — ^We have a pit in the ob- 

 servatory ready prepared for this purpose, through which the heavens may be 

 viewed, and useful observations made, &c. 



Observations concerning the Comet seen in Brasily March 1668, by P. Valentine 

 Estancel a Jesuit, and printed at Rome, in the Qth Italian Giornale de Letterati, 

 Sept. 3\, 1^73. N°105, p. 91. 



This is the same Comet as that noticed in N° 35 of these Tracts. There has 

 not been a phenomenon this great while, of which before this, we have had ob- 

 serv^ations from all parts of the world. Those from Europe and Asia may be 

 seen in our 3d and 4th Giornale. Now I have received those of America, 

 made in the city of St. Salvador, in the southern latitude of 12 deg. A7 min. 

 Likewise the Jesuit P. Pietro Susarte, rector of Macao, in the East Indies, 

 writes to have seen the same all along the coast of Bona Speranza. As to the 



