o/ Thomas Wright of Durham. 245 



a common Center, should be any way irrational, or unna- 

 tural?" 



The sixth letter is headed ' Of General Motion amongst 

 the Stars, the Plurality of Systems, and Innumerability of 

 Worlds.' That the stars are not promiscuously dispersed, he 

 argues from the phaenomenon of the milky way, supposed to 

 be resolvable into stars. He then proceeds to say, "If any 

 regular Order of the Stars then can be demonstrated that will 

 naturally prove this Phaenomenon to be no other than a cer- 

 tain Effect arising from the Observer's Situation, I think you 

 must of course grant such a Solution at least rational, if not 

 the Truth ; and this is what I propose by my new Theory." 

 Afterwards he adds, " .... we may reasonably expect, that 

 the Via Lactea^ which is a manifest Circle amongst the Stars, 

 conspicuous to every Eye, will prove at last the Whole [crea- 

 tion] to be together a vast and glorious regular Production of 

 Beings, .... and that all its Irregularities are only such as na- 

 turally arise from our excentric View : To demonstrate which 

 absolutely and incontestibly, we shall only want this one Pos- 

 tulata to be 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 considers 

 such a phaenomenon established by various instances, and 

 particularly by Arcturus, from comparison with old observa- 

 tions, after allowance for the varying obliquity of the ecliptic. 

 He then recommends close observation of the distances be- 

 tween 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 phaeno- 

 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 perpetual 

 Changes of the Planets, both with regard to their* heliocen- 

 tric 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 



* ''Not to mention tlu'ir several Conjunctions and Apnlces to fixed Stars, 

 &c. sec the State of the Heavens in l(i()!2, Dcccmlwr the first, when all the 

 known Planets were in one Sign of the Zodiac, viz. Sagillariua." 



