X 
PREFACE. 
been derived. Discoveries, when once communi- 
cated to the world, become public 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. 1835. 
* Brett's Principles of Astronomy, p. v. 
