DE MORGAN'S ACCOUNT OF WRIGHT'S SPECULATIONS 197 



granted, viz. that all the Stars are, or may be in Motion" 

 From thence, presuming the stars to have each its attendant 

 system, and arguing that the motion of each primary itself 

 is no more extraordinary than the motion about its axis 

 (which the sun has), he proceeds to discuss the evidence, 

 as it then existed, for apparent proper motion, and con- 

 siders such a phenomenon established by various instances, 

 and particularly by Arctums, from comparison with old 

 observations, after allowance for the -varying obliquity of 

 the ecliptic. He then recommends close observation of 

 the distances between each two stars in a cluster, for 

 detection of the proper motions, and ends this letter with 

 an engraving of the Pleiades, laid down from his own 

 observations. 



The seventh letter gives the explanation of the pheno- 

 menon of the milky way, as now generally received. The 

 following are the first words in which this explanation was 

 ever offered, as it turns out. "But of this I have said 

 enough, and think it is now more than Time to attempt 

 the remaining Part of my Theory. 



"When we reflect upon the various Aspects, and per- 

 petual Changes of the Planets, both with regard to their * 

 heliocentric and geocentric Motion, we may readily imagine, 

 that nothing but a like excentric Position of the Stars could 

 any way produce such an apparently promiscuous Difference 

 in such otherwise regular Bodies. And that in like manner, 

 as the Planets would, if viewed from the Sun, there may 

 be one Place in the Universe to which their Order and 

 primary Motions must appear most regular and most 

 beautiful. Such a Point, I may presume, is not unnatural 

 to be supposed, although hitherto we have not been able 

 to produce any absolute Proof of it. See Plate XXV. 

 This is the great Order of Nature, which I shall now 

 endeavour to prove, and thereby solve the Phenomena of 

 the Via Lactea ; and in order thereto, I want nothing to 

 be granted but what may easily be allowed, namely, that 

 the Milky Way is formed of an infinite Number of small 

 Stars. 



1 Not to mention their several Conjunctions and Apulces to fixed 

 Stars, &c., see the State of the Heavens in 1662, December the first, 

 when all the known Planets were in one Sign of the Zodiac, viz. 

 Sagittarius. 



