1873.] lOO [Chase. 



Let us assume the correctness of the following values : 



Constant of aberration (Struve) 497.827 



Theoretical velocity of sound (Enc. Metrop. ) 916.322 



Mass, Earth -- Sun (Newton) 4.432 ( paralIax ) 3 



* V iooo ' 



Earth's radius (Norton) 3902.8 



The foregoing - proportionality will then yield the following results : 

 Velocity (Light -=- Sound) = j\ C 23 -=- C_ s = 32* = 



mr -5- 32 = 1,048,570 



Velocity of Light (1,048,576 X 916.322 h- 5280) 181,976 



Distance of Sun (1-31,976 X 497.827) 90,592,565 



Parallax (1,296,000" X 3962.8) -h (2- X 90,592,565). . 9". 0227 



Mass, 4.432 (par -*- 1000) 3 1 -^ 307,178 



Mass < radius, (Sun ~h Earth) = 32 5 33,554,432 



Radius (Sun ~ Earth), 33,554,432 -+- 307,178 109.23 



Sun's semi-diameter, 9".0227 X 109.23 985".5 



The most careful estimates of the Sun's actual semi-diameter vary 

 between 961".82 (Br. Naut. Almanac), and 962".1025 (Lockyer), being 

 about 2^ per cent, less than the above theoretical value. In considera • 

 tion of the fact that no allowance has been made for orbital eccentricity, 

 sethereal condensation, mean atmospheric elasticity, or other modifying 

 influence, so close an approximation is very satisfactory. If the theoret- 

 ical velocity of sound were increased | of one per cent, in consequence 

 of such allowances, we should have : Sun's distance, 91,158,769 ; parallax, 

 8".966 ; mass, 312,973 ; radius, 107.21 ; semi-diameter, 961".25. The 

 most recent astronomical estimates of solar distance range between 

 91,186,000 (Winnecke), and 92,380,000 (Newcomb). 



In a former communication (ante, xii. 399), I assigned 91,965,500 miles 

 as a theoretical upper limit of the Earth's possible mean distance from 

 the Sun. For reasons which seem to me still more conclusive, I am in- 

 clined to regard the above approximation of 90,592,565 miles as the lowest 

 possible limit, and I shall look with much interest and confident expect- 

 ation, for a confirmation of these estimates by the observations of the 

 approaching transit of Venus. 



The inverse proportionality of velocity to wave-length suggests a fur- 

 ther extension of the comparison. Airy's estimate of the time required 

 for the solar disturbance of July 7th, 1872, to affect the terrestrial mag- 

 netism, would make the luminous velocity (2 h. 20 m. 4- 497.827 s. =) 

 16.87 X the magnetic. This estimate would be increased if the out- 

 burst took place before it was observed by Father Secchi, but it is not to 

 be supposed that it could be doubled. If the Sun's distance is 90,592,565 

 miles, the theoretical explosive range of hydrogen should be 4 (90,592,565 

 -h 307,198) = 1179.7 ; (3962.8 + 1179.7) -=- 294.92 _ 17.4. This appears 

 to indicate a magnetic gamut, four octaves below that of light, bearing 

 the same relations to the luminous octave, in frequency of undulation, as 

 a single vibration of a pendulum bears to the lowest number of vibrations 

 A. p. s. — VOL. XIII. T 



