296 Biographical Account of DR WILSON, 



siderata. Between this last step, and the accomplishment of a 

 profound discovery, he conceived that the transition might some- 

 times be made with no great effort of invention, by only sifting 

 carefully such principles as are already known and familiar to us, 

 and availing ourselves of them in their full extent. 



It was by proceeding in this way, and, when considering the 

 manner by which the motion of light would be affected by re- 

 flecting and refracting media, themselves moving with great ve- 

 locity, (a most interesting field in Optics, then wholly unculti- 

 vated), that two principles came into view, either of which may 

 possibly serve us in detecting a general motion belonging to the 

 solar system, relatively to the surrounding fixed stars, or in pro- 

 ving a negative with regard to it. Of these, a very summary ac- 

 count has been given in the historical part of the Edinburgh 

 Philosophical Transactions, vol. i. But, should they be success- 

 ful in discovering such a concealed motion, the same principles 

 cannot fail of determining the velocity and direction of it ; and, 

 in process of time, whether such a translation of the whole sys- 

 tem be in a straight line or a curve, and if in a curve, whether it 

 be of such a kind as may indicate a periodical revolution. And 

 it needs scarce be mentioned, that if such a thing should actu- 

 ally be made out, besides enriching astronomy with that know- 

 ledge which depends upon measurable parallaxes in the sphere 

 of the starry firmament ; it would also bestow a very high autho- 

 rity upon Dr WILSON'S suggestions, of what possibly may be the 

 plan of Nature in upholding the universe. 



At the time of the last-mentioned publication, he was sixty- 

 three years old, but still continued to enjoy the blessings of an 

 uninterrupted state of good health. In the year 1784, at the 

 recommendation of the University, his Majesty was graciously 

 pleased to nominate and appoint PATRICK WILSON, A. M., Dr 

 WILSON'S second son, to be assistant and successor to his father, 

 as Professor of Practical Astronomy and Observer ; a circum- 



