5 INTRODUCTORY. 



whole diameter of the earth is less than ^ of the distance 

 of the sun, and the astronomer is in the predicament of a 

 surveyor, who, having to measure the distance of an object 

 ten miles off, finds himself restricted to a base of less than 

 five feet, and herein lies the difficulty of the problem. 



Of course, it would be hopeless to attempt this problem 

 by direct observations, such as answer perfectly in the case 

 of the moon, whose distance is only thirty times the earth's 

 diameter. In her case, observations taken from stations 

 widely separated in latitude, like Berlin and the Cape of 

 Good Hope, or Washington and Santiago, determine her 

 parallax and distance with very satisfactory precision ; (very 

 unsatisfactory, rather, since the error is very nearly half of 

 one per cent. — Author) but if observations of the same 

 accuracy could be made upon the sun, (which is not the case, 

 since its heat disturbs the adjustments of an instrument) they 

 would only show the parallax to be somewhere between 8" 

 and io", — its distance between 126,000,000 and 82,000,000 

 miles. 



Astronomers, therefore, have been driven to employ 

 indirect methods, based on various principles. 



On the Method of Zadig. 



From a Lecture by Huxley. 



It is a usual and a commendable practice to preface the 

 discussion of the views of a philosophic thinker by some 

 account of the man. and of the circumstances which shaped 

 his life and colored his way of looking at things ; but, 

 though Zadig is cited in one of the most important chapters 

 of Cuvier's greatest work, little is known about him, and 

 that little might, perhaps, be better authenticated than it is. 



