Solar Eclipse of July 28, 1851. 105 



the progress of the phenomenon, so as to avoid fatiguhig the 

 eyes ; the graduated circle would enable us to refer any 

 appearance to the proper place on the sun's disc. With the 

 lowest power, the sun*s image on this screen is about 7J 

 inches in diameter ; the spots with their surrounding um- 

 brae, the variegation of the sun's surface, and its gradual 

 diminution in apparent brilliancy towards the edge are 

 beautifully distinct. In this way we had examined the in- 

 gress of Mercury ; the progress of the planet was distinctly 

 followed without any appearance of that distortion which is 

 mentioned in the Committee's suggestions. Hence I ex- 

 pected that this instrument would afford conclusive evidence 

 concerning the nature of the beads. 



The owner of this refractor procured from the same maker 

 a splendid equatorial of 14J inches aperture, completely 

 mounted, for the Ottoman Government; this magnificent 

 instrument has not yet been set up. 



For the purpose of determining our geographical position, 

 we had an 8 inch portable astronomical circle, by Adie of 

 Edinburgh, the performance of which has long given me the 

 greatest satisfaction. It is read to 10" with three verniers, 

 both in altitude and in azimuth, and is fitted with all the 

 adjustments which an instrument of that size can require. 

 This was accompanied by a chronometer, whose rate had, for 

 several years, been found sufficiently steady, with a slight 

 over-compensation, that is, a tendency to go faster in summer. 

 Its winter rate had been Os. 9 losing, and its summer rate 

 was Os. 24 losing. For comparison we had also a pocket- 

 watch, whose rate was as close as that of the chronometer. 

 A mountain-barometer for correcting the refraction, a pair 

 of Nicol's eye-pieces, darkening glasses, boxes of tincture of 

 litmus of various thicknesses, stearine candles for comparing 

 shadows, and other odds and ends completed the apparatus. 



Encountering only light winds and calms, we saw our 

 prospects of reaching Kertche gradually wane ; computa- 

 tions for Theodosia were made, and instructions were drawn 

 up for a nearly tangential phase. Latterly we had been 

 hoping against conviction, when, on sighting the south point 

 of the Crimea, our hopes were revived by a fresh breeze. 



