THE SOLAR SYSTEM. 



and that to an Infinite God there is no difficulty from 

 such sources. 



THE SOLAR SYSTEM. 



This is the name given to that collection of worlds which, 

 with the sun as a centre, circulate at different distances 

 from and around it. There have at present been discovered 

 eight large planets and thirty-four smaller ones called 

 " asteroids " or "planetoids," the larger planets revolving in 

 the following order from the sun or centre : 



1. MERCURY. 5. JUPITER. 



2. VENUS. 6. SATURN. 



3. THE EARTH. 7. URANUS. 



4. MARS. 8. NEPTUNE. 



The Sun, the centre of the solar system, is the great source 

 of light and heat to our planet and all others which revolve 

 around it, as well as of another agent not so well understood, 

 namely " actinism," or that power which produces the 

 chemical changes in many substances exposed to the sun's 

 rays, and which has been of late turned to such useful 

 and wonderful account in the art of photography. 



The sun is an immense sphere, many thousand times 

 larger than our earth, or indeed all the planets put together. 

 It turns upon its axis in twenty-five days, and, like all 

 spheres which rotate, has a slightly flattened form; it is 

 supposed that the sun itself, carrying its planets with it, 

 performs a journey round some other centre very far away, 

 but for all the purposes of explaining the solar system it 

 may be supposed to be stationary. The diameter of the 

 sun is about 890,000 miles, or nearly 112 times the diameter 

 of our earth, and as the bulk of spheres is as the cubes 

 of their diameters, it follows that the sun is about 1,400,000 

 times the bulk of the earth. Fig. 1 shows the relative size 

 of the sun and the planets which rotate round it ; the specific 

 gravity of the sun is about a quarter that of our earth or one- 

 and-a-half times that of water. On its surface irregularities 

 are seen (by the aid of the telescope) which give it a wavy 

 appearance, and beside these, black spots or tracts (macula;) 



B 2 



