MAGNITUDE. 



equal in magnitude to the moon, it would assuredly appear fou% 

 hundred times less at four- hundred times a greater distance: but 

 since at that greater distance it does not appear less or greater, but 

 of the same magnitude, the irresistible conclusion, level to the 

 apprehension of any understanding, is, that the sun must in reality 

 be four hundred times greater in its diameter than the moon. If 

 it were less, at four hundred times the moon's distance, it would 

 appear less than that of the moon ; if it were greater, at that dis- 

 tance it would appear greater. It follows, then, that whatever 

 be the magnitude of the diameter of the moon, the diameter of the 

 sun must assuredly be four hundred times greater. Now it has 

 been ascertained by absolute measurement that the diameter of 

 the moon measures about 2000 miles. If we multiply this by four 

 hundred we shall obtain 800000 miles, which is, therefore, the 

 diameter of the sun. 



These calculations have been made roughly and in round num- 

 bers ; more accurately, the diameter of the sun measures 882000 

 miles, but as we recommend the adoption of round numbers, we 

 shall call the sun's diameter 900000 miles. Such is the stu- 

 pendous mass placed in the centre of the system which, by its 

 attraction, coerces the movements of the planets. 



4. Such magnitudes and distances are so far beyond all the ordi- 

 nary standards with which we are familiar, that the imagination 

 is confounded and falls back upon itself after any effort to form 

 a distinct conception of them. Let us see whether we cannot 

 discover some expedient or some means of illustration by which a 

 more distinct notion can be obtained of the distance and magnitude 

 of this stupendous globe. 



A railway-train moving at thirty-two miles an hour would take 

 three millions of hours or an hundred and twenty-five thousand 

 days, or three hundred and forty-two years and three months to 

 move from the earth to the sun, supposing it to travel incessantly 

 night and day for that time ! 



A cannon ball moves fifty times as fast as such a railway train. 

 It would therefore move to the sun in a little less than seven 

 years ! 



To give some idea of the dimensions of the sun we are to con- 

 sider that having a diameter of 882000 miles, its circumference 

 will be about 2,770000 miles. Such a railway-train would take 

 nine years and ten months to travel round it. 



We know that the moon revolves in a circle round the earth at 

 the distance of nearly a quarter of a million of miles. Now let us 

 suppose the earth to be placed at the centre of the sun. The 

 distance of the outer surface of the sun from the centre of the 

 earth would be 441000 miles. Now the circle in which the 



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