Proctor J 8 Astronomical Lectures. 



THE SUN'S Mianr. 



Now let us consider the might that resides in the 

 eun. If the suii were merely an orb very much 

 larger than the earth, as we see he is, there might 

 still not he the force necessary to the sun as a ruler 

 over the earth. Let me give you an idea of how- 

 large the sun ia. I am in the habit, in England, 

 when I wish to speak of the siza of the sun, of 

 informing my audience that " this country (England) 

 in which we live, which seems to us so large, ia 

 nevertheless small by comparison with the earth, for 

 if the earth were one inch in diameter, England 

 would be a small triangular speck, which you could 

 scarcely recognize." But I am afraid that to an 

 American audience that comparison would be im- 

 perfect. In fact, I have heard that an American 

 traveling in England found the country so small 

 that he at once sought the central counties, and was 

 even then afraid to go out in the evening for fear of 

 falling off the little island. [Laughter.] We in 

 England, whether it be the natural courage of our 

 disposition or the effect of longhabit, are not troubled 

 with that feeling. But even America is so small 

 compared with the sun, that if there were a 

 spot upon the sun as large as the whole of America, 

 it would be quite invisible to the naked eye. In- 

 deed, if an object as large aa the earth were placed 

 immediately before the sun, and there appeared as a 

 black disk, it would nevertheless require a large 

 telescope to make it visible ; 108 times does the sun's 

 diameter exceed that of the earth, and the surface of 

 the sun exceeds that of the earth 108 tirnea 108 times, 

 or 11,600 times, while the volume of the su,n exceeds 

 that of the earth 1,250,000 times. But the mass of 

 the sun is not so much greater than the earth. It 

 would appear aa thoush the body of the sun wero 

 constituted of matter about a quarter lighter on au 

 average than that which constitutes the earth, and 

 the result is that the suu'a mass instead of exceeding 

 the mass of the earth 1,250,000 times, only exceeds it 

 815,000 times. But only consider what that means! 

 If this earth were to grow in density until its mass 

 were equal to that of the sun, then a half-ounce 

 weight one of those that are used to balance our 

 letters would weigh 4* tons. A man of average 

 weight would be drawn to the earth as a weight of 

 20,000 Ions. An object raised from the earth a single 

 inch would, in falling that short distance, acquire 

 a velocity three times greater than that of an express 

 train. Such ia the might with which the sun rules 

 this earr.li. 



Till SOURCE OF HEAT AND LIGHT. 



But, now let us pass from the question of the sun's 

 might to its heat and light. The sun is the source 

 of all these forms of light and life which exist upon 

 the earth. That ia no idle dream. Every form of 

 force upou the earth, every action that we perform, 



all the forms of energy we know of, even the very 

 thoughts we think, may be said to coma from the 

 sun. It is by the sun's heat that life is maintained 

 upon the earth. 



And now as to the quantity of that heat. Sir John 

 Herschel in the South of Africa made experiments 

 to determine the actual quantity of heat 

 that is received from the sun. The heat 

 thsre was so great that at the depth of 

 four inches below the sand tho thermometer 

 rose to 160. He was able to cook a steak by placing 

 it in a box covered with glass, and that inside 

 another box with a glass cover; and to boil eggs 

 hard. He made experiments, and found in the first 

 place that about one-fourth of the sun's light and 

 heat were cut off at midday by the air, and taking 

 that into account, and making the requisite calcula- 

 tion for a largo extent of surface, he found that the 

 quantity of the sun's heat that fell on an area of one 

 square mile would be sufficient to melt in a single 

 hour 26,000 tons of ice. Well, now that is merely 

 the quantity received by a square mile 

 of the earth'a surface. But the earth presents 

 to the sun a surface (regarding her for 

 a moment aa a flat disk) 50,000,000 square 

 miles in extent. And then how small is the 

 quantity of the sun's light and heat that thia earth 

 actually captures. You have only to consider 

 how small the sun looka in the heavens, and 

 consider how small our earth would look beside him, 

 with this small diameter compared with his, of one 

 inch to three yards, and you can aee how small a 

 proportion of the sun'a heat we capture. B\ r a cal- 

 culation which can be readily made, it is found that 

 only the 2,000,000,000th part, or less than that pro- 

 portion, of the sun's heat ia captured by the earth; 

 and all the planets together receive only one 

 227,000,000th part of the sun'a heat. Here is another 

 mystery the study of astronomy presents. Oaly one 

 part in 227,000,000 parts appears to be applied to any 

 useful purpose, and the rest seems wasted. It 

 is not for us to judge of the operations of Nature. 

 But here at any rate do we ssern to find a confirma- 

 tion of the saying of the atheist that sounds so 

 strange tc us, that " Nature in filling a wine-glas 

 upsets a gallon." There ia the sun's heat being con- 

 tinually sent forth, and only the 227,000,000th part 

 received. Only imagine a merchant who spent 

 large sums of money, and who employed 

 only one cent usefully for every $3,000,000 

 of hia income. And that is what > the 

 sun appears to be continually doing/ -'The 

 actual emission of solar light and heat corresponds 

 to what would bo obtained if on every square yarf 

 of the sun's surface six tons of coal were conaumet. 

 every hour. In every second the sun gives oci ft 

 much heat aa would be given out by bom* m 



