Prof. Struve on the large Refracting Telescope, c$r. 105 



The Pholades are regularly used as an article of food on 

 the coasts of France and Italy, where they abound. In the 

 neighbourhood of Dieppe, bands of women and children, each 

 armed with a pick-axe, break the rocks inhabited by them, 

 for the purpose of sending them to market, or as bait for fish. 

 They are found in every sea where the rocks are suitable for 

 their burrowing, and are met with fossil in many countries of 

 Europe.* 



Art. XXII. — Farther Account of the large Achromatic Re- 

 fracting Telescope of Fraunhqfer in the Observatory of 

 Dorpat. By Professor Struve. 



In the Fourth Number of this Journal we have already 

 given an engraving, and a brief description, of this fine in- 

 strument; but as a detailed account of it has just been pub- 

 lished by Professor Struve himself, -f* we shall now present our 

 readers with a more minute description. 



As soon as Professor Struve had put up the instrument 

 he directed it to the moon and some double stars. " I stood 

 astonished, 1 " says he, " before this beautiful instrument, unde- 

 termined whether to admire most, the beauty and elegance of 

 the workmanship in its most minute parts, the propriety of 

 its construction, the ingenious mechanism for movino- it, or 

 the incomparable optical power of the telescope, and the 

 precision with which objects are defined. 



When in a perpendicular position, the height of the object 

 glass is 1G feet 4 inches (Paris measure) from the floor, 13 

 feet 7 inches of which belong to the telescope itself, so that 

 the eye-glass stands 2 feet 9 inches from the floor. The 

 weight of the whole instrument is about 3000 Russian pounds, 

 of which 1000 belong to the frame-work, &c. which supports 



• Bosc in Nouv. Diet. d'Hist. Nat. vol. xxv. p. 593. M. G. P. Des- 

 hayes has recently described and figured four species of fossil Pholades, 

 found by him, among other perforating bivalves, at the village of Valmon- 

 dois, in France. — Mem. de la Soc. d'Hist. Nat. torn. i. p. 245. 



t In the Memoirs of the Astronomical Society of London, vol. ii. part i. 

 p. 93. 



