664 PHILOSOPHICAL TfiANSACTIOXS. [aNNO 1723. 



A Collection of Geometrical Flowers, presented to the Royal Society. By Guido 

 Grandi, Abbot of the Camaldules, and Professor of Mathematics at Pisa. 

 N** 378, p. 355. 



This handful or bouquet of geometrical roses, is a dissertation on certain 

 curves geometrically described in a circle, of a nature more curious and fanci- 

 ful, than any way useful. This paper the author afterwards enlarged in another 

 separate treatise published in 17^8, entitled, Flores Geometrici ex Rhodonearum, 

 &c. where the subject may better be consulted in its improved state. 



Concerning Observations made uith Mr. Hadleys Reflecting Telescope. By the 

 Rev. Mr. James Pound, Rector of fVanstead, F. R. S. N'' 378, p. 382. 



It were to be wished, that, with the particular description given in the 

 Transact. N° 376, of the curious mechanism of that catadioptric telescope 

 which was made by Mr. Hadley, and presented to the Royal Society, he had 

 communicated also a full account of what observations he had made with it, 

 that the public might have been apprised of the usefulness of an invention, 

 worthy of its great author, Sir Isaac Newton, which, perhaps from the vain 

 attempts made by some of putting it in practice, has lain neglected these 50 

 years ; the time since which it was first published in the Philos. Transactions, 

 (N^81.) 



Mr. Hadley has sufficiently shown, that this noble invention does not consist 

 in bare theory ; and it is to be hoped that he, or some other such curious per- 

 sons, will in a short time find out a method, either of preserving the concave 

 metal from tarnishing, or of clearing it easily when tarnished, or else of making 

 a good concave speculum of glass quicksilvered on the back part. When a 

 method for either of these shall be discovered, it is not to be doubted, but that 

 the old dioptric telescope will be for the most part laid by, and this catoptric 

 one will be chiefly in use among practical astronomers ; as several inconveni- 

 encies and difficulties, which are unavoidable in the management of the former, 

 especially when long, are in the latter entirely avoided. 



It is no small convenience, that by means of one of these reflecting tele- 

 scopes, not exceeding 5 feet in length, and which may be managed at a window 

 within the house, celestial objects appear as much magnified, and as distinct, as 

 they do through the common telescope, of more than 100 feet in length. 



Mr. Bradley, Savilian professor of astronomy, and myself, have compared 

 Mr. Hadley's telescope, in which the focal length of the object metal is not 



