54 SCENERY OF THE HEAVENS. 



of his varying distance ; the length of time during which they act continuously, and 

 their direction being more or less oblique. When he is farthest from us, as in summer, 

 he is daily above the horizon twice as long as when he is nearest, at the winter solstice. 

 His continued action causes a powerful accumulation of heat, and the nights being 

 short, but little of it is radiated, or given off during his absence. But temperature 

 is affected by the direction of the sun's rays, whether vertical or oblique, their 

 greatest force being experienced when they are perpendicular to the surface, while in 

 proportion as they are oblique, they glance off, and having to pass through a larger 

 portion of the atmosphere, a larger number are absorbed and dispersed by it. Out of 

 ten thousand rays falling upon the earth's atmosphere, 8123 arrive at a given point if 

 they come perpendicularly, 7,024 if the angle of direction is fifty degrees, 2,831 if it is 

 seven degrees, and only 5 if the direction is horizontal. Now, in summer, the sun being 

 north of the equator, he rises to a greater altitude in the heavens ; his rays reach us in a 

 more vertical direction, and the days being longer than the nights, more heat is absorbed 

 than what is radiated. But in winter he traverses those signs of the zodiac that are south 

 of the equator ; and, ascending to a less elevation in the heavens, his rays reach us more 

 obliquely, and the days being short, the solar action is less continuous : hence in summer 

 we have the greatest heat though the earth is then farthest from the sun ; and in winter 

 the greatest cold when it is at the nearest point. 



The mean distance of the sun from the earth, as determined by observation of the 

 transits of Venus, is ninety-five millions of miles ; and according to Laplace, this must be 

 within -g^ of the true distance, so that no error is involved either way greater than about 

 a million of miles. The immense magnitude of the solar body appears from the fact, that 

 he occupies so much space in the heavens, and presents such a stately aspect, with so vast 

 an interval between us. If a locomotive had been started five centuries and a half ago 

 at the termination of the Crusades, and had been travelling incessantly at the rate of 

 twenty miles an hour, it would only now just have accomplished a space equal to that 

 which lies between the terrestrial and the solar surface. Though light comes to the 

 former from the latter in about eight minutes, a cannon ball would not perform the same 

 feat, retaining its full force, under twenty- two -years. That an object therefore should be 

 so splendidly visible as the sun, so far removed, and should so powerfully influence us with 

 light and heat, argues the stupendous dimensions of his volume. His direct light is 

 supposed to be equal to that of 5570 wax candles placed at the distance of one foot from 

 an object ; and so great is the power of his rays, that some of the men employed in con- 

 structing the Plymouth Breakwater had their caps burnt in a diving bell thirty feet under 

 water, owing to their sitting under the focal point of the convex glasses in the upper 

 part of the machine. His real diameter of 882,000 miles is equal to 111^ times that of 

 the earth ; and his circumference of 2,764,600 miles describes a bulk nearly a million and 

 a quarter times larger than our own globe, and above five hundred times greater than 

 the united volume of all the planetary bodies that revolve around him. If his mass occu- 

 pied the place of the earth, it would fill up the entire orbit of the moon, and extend into 

 space as far again as the path of that satellite. The density of the solar substance is, 

 however, far less than that of the matter of our globe. If the two bodies could be 

 weighed in a balance, the weight of the sun would not preponderate in the same 

 proportion as his bulk, but be only 354,936 times heavier. This proportion is about a 

 fourth less than that of his magnitude ; so that the same extent of solar substance would 

 be found four times lighter than the same extent of terrestrial substance. 



To the naked eye the disk of the sun ordinarily presents a surface incomparably 

 brilliant and uniformly luminous. There is no spot, or wrinkle, or blemish. The perfect 

 purity of his aspect was an article of faith universally received by the ancient world. It 



