436 Sun Vieiving and Drawing. 



phenomena on only a very small scale. A yet more striking 

 instance of both the bizarre and grotesque combined might 

 have been adduced by the writer in the case of a magnificent 

 group of spots which was thus alluded to in a paper read by 

 him before the Eoyal Astronomical Society:* — "I have only 

 one more subject to mention, and that is, that I hope some 

 one else beside myself took notice of and depicted, or, better 

 still, secured a photograph, of a most curious phantom-looking 

 group of spots, which at 1 p.m. on the 4th January of this 

 present year (1863) exhibited an appearance so wonderfully 

 like a human skeleton that, in a less superstitious age than the 

 nineteenth century, its portentous shape might easily have 

 raised considerable apprehension in the minds of the multitude. 

 -Being Sunday when this was observed, and being much 

 occupied with the more immediate duties of the day, I did not 

 draw the group with micrometric correctness, but simply took 

 a rough sketch of the phantom, which subtended about 5' 40" 

 of arc of the solar surface, or 153,000 miles, and respecting 

 which (as I observed lately to Admiral Mannersf) I am really 

 not aware that any love for the marvellous induced me to 

 exaggerate in any degree the singularity of its proportions. 

 Sheet 96 exhibits this group as it appeared, when much altered, 

 on January 7th." 



Having already alluded to the most convenient way of pro- 

 jecting the sun's image on the screen, we now proceed to 

 explain how the spots, etc., may be accurately measured. 

 Cause your optician to rule for you on a circular piece of 

 glass a number of fine graduations, the - e ( 'oth part of an inch 

 apart, each fifth and tenth line being of a different length, 

 in order to assist the eye in their enumeration. Insert this 

 between the anterior and posterior lenses of a Huygenian eye- 

 piece of moderate power, say 80 linear. Direct your telescope 

 upon the sun, and having so arranged it that the whole disc 

 of the sun may be projected on the screen, count carefully the 

 number of graduations that are seen to exactly occupy the 

 solar diameter. A correct eye is requisite in order to judge 

 precisely where any one diameter lies. By means of practice, 

 however, this may soon be done with the greatest facility; 

 and, inasmuch as the sun's disc is a perfect sphere, being 

 neither oblate nor prolate in the slightest appreciable degree, % 



* See Monthly Notices, Royal Astronomical Society, vol. xxiii., p. 273, for 

 Nov. 1863. 



t The Foreign Secretary of the "Royal Astronomical Society. 



X This is the dictum of our present Astronomer Royal, Professor Airy ; and 

 Professor Braylev,in a very interesting article^on the physical constitution of the 

 sun, in the Companion to the Almanack, for 186 1, says, that "the sun is the only 

 body of the solar system having that figure, and the only known example of a 

 perfect sphere in nature." 



