Fig. 2. 



-X. 



touch the sun, but will perhaps fall a little within it, as represented in the an- 

 nexed figure, 3. 



Fig. 3. 



And after a further lapse of time, he will find, on the other hand, that they 

 fall a little without it, as in the following figure, 4. 



Fig. 4. 



Now, as the wires throughout such a series of observations are maintained s 

 always in the same position, it follows that the disk of the sun must appear ? 

 smaller at one time, and larger at another that, in fact, the apparent magni- s 

 tude of the sun must be variable. It is true that this variation is confined within ) 

 very small limits, but still it is distinctly perceptible. What, then, it may be 

 asked, must be its cause ? Is it possible to imagine that the sun really under- 

 goes a change in its size ? This idea would, under any circumstances, be ab- 

 surd ; but when we have ascertained, as we may do, that the change of apparent 

 magnitude of the sun is regular and periodical that for one half of the year 

 it continually diminishes until it attains a minimum, and then for the next .'lalf 

 year it increases until it attains a maximum such a supposition as that of a 

 real periodical change in the globe of the sun, becomes altogether incredible. 



If, then, an actual change in the magnitude of the sun be impossible, there 

 is but one other conceivable cause for the change in its apparent magnitude 

 which is, a corresponding change in the earth's distance from it. If the earth 

 at one time be more remote than at another, the sun will appear proportionally 

 smaller. This is an easy and obvious explanation of the changes of appear- 



