73 



III. " Notes on the Drawing of ' Copernicus/ presented to the 

 Royal Society by P. A. SECCHI." By JOHN PHILLIPS, 

 Esq., F.R.S. Communicated by Col. SABINE, V.P. & 

 Treas. R.S. Received April 9, 1856. 



Of the few attempts which have been made of late years to pre- 

 pare drawings*, on a large scale, of selected lunar mountains, this 

 contribution from the Roman Observatory appears to be one of the 

 most successful. It is on a scale o"f" magnitude (about 10 geogra- 

 phical miles to one inch) such as only the larger modern telescopes 

 can command, and characterized by such firmness of definition as to 

 do honour alike to the maker of the instrument and to the artist 

 engaged in the delineation. It may assist those who have not 

 attempted, with their own hands, any drawings of this kind, and 

 desire to form a right judgement of the value of this work of 

 P. Secchi, if I send for comparison a drawing of Gassendi, executed 

 from my object-glass of 6^ inches (Cook), with a focal length of 

 1 1 feet. The drawing is on a scale of 20 geographical miles to an 

 inch, and Gassendi thus appears of half the linear dimension of 

 Copernicus, being really almost of the same diameter. 



Placing together the two drawings, and remembering the appear- 

 ance of Copernicus, as I have seen it through telescopes, some re- 

 flections arise which it may be permitted me to express, in the hope 

 that we are now fairly entered on the long career of discoveries in 

 the moon, to which the attention of astronomers has been of late 

 systematically drawn by the Earl of Rosse and a Committee of the 

 British Association. 



In proportion as the power of the telescope rises, the seemingly 

 simple 'ring mountains' of the moon exhibit as much diversity of 

 outline and structure as the larger terrestrial volcanoes when accu- 

 rately mapped. Thus while Gassendi, 40 from the central meri- 

 dian of the moon, and 17 south f of the equator, has the obliquely 

 elliptical contour due to a circle in that position, Copernicus, 20 



* As distinct from mere plans. The drawings must however be based on exact 

 plans. 



t The Poles being named after the type of Madler's noble work, ' Der Mond.' 

 VOL. VIII. H 



