136 HERSCHEL AND HIS WORK 



When he had proceeded some way in his inquiries, 

 he received from a friend a copy of a catalogue of 

 eighty stars made by Mayer of Gottingen in 1756, 

 "and compared with the same stars as given by 

 Roemer in 1706." Both Roemer and Mayer were men 

 of the highest ability. Previously he knew this 

 catalogue only in an extract which he found in a 

 French book on astronomy. Setting to work on the 

 new material thus furnished, and laying aside thirteen 

 or fourteen of the stars as those he had already 

 examined, he separated the others into two classes, 

 those which went for his view of a motion of the 

 sun through space, and those whose motions "must 

 be ascribed to a real motion in the stars themselves." 

 Mayer, admirable astronomer though Herschel admitted 

 him to be, did not countenance the idea of a motion 

 of the sun with all its planets through space. 

 "Were it so," he wrote in 1760, "were the sun and 

 all the planets and our home, the earth, advancing 

 towards some quarter, all the stars in that part of 

 the heavens would seem to open out, and those in the 

 opposite quarter to come together, just as, when you 

 are walking through a wood, the trees which are 

 in front of you seem to separate from each other, 

 and those which are behind to draw closer." 

 Herschel, seizing on Mayer's illustration of trees in 

 a wood, declared that these very changes were taking 

 place among stars in the heavens. At the same time 

 he was encouraged by a short tract sent him by the 

 author, Dr. Alexander Wilson, Professor of Astronomy 

 at Glasgow, and printed in 1777, entitled Thoughts 

 on General Gravitation and Views thence arising as to 

 the State of the Universe. A friendship sprang up 



