54 THE SUN. 



another ; the one in the northern hemisphere, the other 

 in the southern, viz., at Hammerfest in Norway, and at 

 the Cape of Good Hope, both very nearly on the same 

 meridian, so that the sun, or the moon, or any other 

 heavenly body attains its greatest altitude above the hori- 

 zon of each (or as astronomers express it, passes the 

 meridian of each) very nearly at the same time. Suppos- 

 ing then that this, its meridian altitude^ is carefully ob- 

 served at each of these two stations on the same day; it 

 is easy to find, by computation, the angles included be- 

 tween each of the two lines of direction in which it was 

 seen from the two places, and their common line of 

 junction; so that taking this latter line for the base of a 

 triangle, of which the two sides are the distances of the 

 object from either place, those two sides can thence be 

 calculated by the very same process of computation which 

 is employed in geographical surveying to find the distance 

 of a signal from observations at the ends of a measured 

 base. Now, the distance between Hammerfest and the 

 Cape in a straight line is nearly 6300 miles, and owing 

 to the situations of the two places in latitude, the triangle 

 in question is always what a land surveyor would call a 

 favourable one for calculation : so that, with so long a base, 

 we may reasonably expect to arrive at a considerably 

 exact knowledge of its sides, after which a litde addi- 

 tional calculation will readily enable us to conclude the 

 distance of the object observed from the earth's centre. 



(8.) When the moon is the object observed, this ex- 

 pectation is found to be justified. The triangle in ques- 

 tion, though a long one, is not extravagantly so. Its 



