SUN POWER. 503 



but perhaps the next transit of Venus will assist the observers to a nearer 

 estimate. It is quite sufficient for our purpose, however, to state that the 

 sun's distance from the earth is 92,000,000 of miles. The distance 

 varies in winter and summer. In the former period the sun is nearer than 

 in summer, and yet as the rays strike over us, and pass us, as it were, we 

 feel less heat. When, as in summer, we are more in the focus of the rays, 

 we feel the greater heat. 



We have already spoken of parallax, and it is by rinding the solar 

 parallax that the distance of the sun from us is found. This parallax has not 

 been exactly ascertained, or rather authorities differ, and as difference of O'Oi" 

 in the solar parallax means something over 100,000 miles of distance, it is 

 evident that exactness is almost impossible. If 8"'8o be settled as the solar 

 parallax, 92,880,000 miles is the distance of the sun from the earth. If 

 <T'8S be taken we have nearly 92,000,000 exactly. 



The volume of the sun is 1,253,000 times that of the earth, and yet the 

 density of the former is only about one-fourth of the latter, so the attraction 

 of gravitation at the sun must be more than that of the earth's surface 

 twenty-seven times. A body dropped near the surface of the sun would fall 

 436 feet in the first second, and have attained a velocity of ten miles a 

 minute at the end of the first second. The diameter of the sun depends 

 in our calculations upon its distance from the earth. If we suppose that to 

 be 92,880,000 miles, the diameter is 866,000 miles. If we take 91,000,000 

 of miles as the distance from the earth the diameter is 850,467 miles. The 

 sun makes (apparently) the circuit of the heavens in 365 days, 6 hours, 

 9 minutes, and 9*6 seconds ; the transit from one vernal equinox to the 

 next being only 365 days, 5 hours, 48 minutes, 48*6 seconds, owing to the 

 precession of the equinoxes already mentioned. 



When we consider the power and grandeur of the sun we may well feel 

 lost in the contemplation. The sun balances the planets and keeps them in 

 their orbits. He gives us the light and heat we enjoy, and coal-gas is 

 merely " bottled-up sunlight." In darkness nothing will come to maturity. 

 We obtain rain and dew owing to the sun's evaporative power ; and no 

 action could go on upon earth without the sun ; and yet we receive only about 



^TTuA-o-Uoo P art of its heat and Kg**- 



As to the colour of the sun, Professor Langley states that it is really 



blue, and not the white disc we see. The whiteness is due to the effect of 

 absorption exerted by the vapourous metallic atmosphere surrounding our 

 luminary ; and if that atmosphere were removed, his colour would 

 change. 





