PREFACE. 



1 



been derived. Discoveries, when once communi- 

 cated to the world, become pubHc property : they 

 are thrown into the common stock for mutual benefit; 

 and it is only in the case of debatable opinions, or 

 of any recent and unconfirmed observations, that it 

 really interests the world that authorities should be 

 quoted at all. In the language of a highly valued 

 friend, when writing upon another subject: — *' The 

 advanced state of a science is but the accumulation 

 of the discoveries and inventions of many : to refer 

 each of these to its author is the business of the 

 history of science, but does not belong to a work 

 which professes merely to give an account of the 

 science as it is : all that is generally acknowledged 

 must pass current from author to author." * 



London, Aug. 1 . 1 835. 



* Brett's Principles of Astronomy, p. v. 



