IQ4 DE MORGANS ACCOUNT OF WRIGHTS SPECULATIONS 



In the first letter Wright gives the opinions of preceding 

 authors. He states that his own system was first planned 

 in 1734. I need not describe his very imperfect enumera- 

 tion of his predecessors. In 1732, Robert Wright, whom 

 I ought to mention to prevent his being confounded with 

 the subject of this notice, published his Newtonian lunar 

 tables for the navy. 



The second letter is on probability and certainty, and, 

 though ingenious and sound, has nothing to the present 

 purpose. It concludes with an account of celestial systems 

 anterior to that of Copernicus. 



The third letter is on the planetary motions and structures. 

 It contains nothing peculiar to Wright, except a declaration 

 that he is strongly of opinion that the orbits of comets have 

 all their areas equal. This is not a happy conjecture. He 

 draws the notion from observing that the comets of 1680 

 and 1682, the most and least excentric of those whose 

 orbits had been calculated, have areas not very unequal, 

 and such as a supposition of moderate errors of observation 

 might make equal. The following sentence is of a better 

 kind, be the latter part worth what it may. ". . . the 

 Clouds are to us in effect no other than as so many Moons, 

 whereby we have our artificial Day prolonged to us several 

 Hours after the Sun is set, and likewise produced as much 

 sooner before he rises ; and were they to ascend by still 

 stronger Power of Exhalation to an Elevation, all round 

 the Atmosphere, so as to form a Sphere equal to four 

 Times the Globe of the Earth, there would then be no 

 such Thing as real nocturnal Darkness to any Part of the 

 World." 



The fourth letter continues his remarks on the nature 

 of the heavenly bodies. That the sun is a vast body of 

 blazing matter, he thinks will hardly admit of question : 

 though he afterwards supposes it possible that the igneous 

 matter may be only an envelope. Aberration is spoken of 

 with caution. " Mr. Bradley, Astronomer-Royal, has, in a 

 great measure, proved that the Aberration of the Stars 

 hitherto mistaken for a Parallax, may arise from, and indeed 

 seems to be no other than the progressive Motion of 

 Light, and Change of Place to the Eye, arising from the 

 Earth's annual Motion and Direction." His friend is 

 recommended to procure an idea of the appearance of the 



