OF FINITE DIFFERENCES. 211 



last terms, unless a is extremely large, in which case other 

 methods of approximating (those, namely, of Laplace), may be 

 made use of. 



Enough has probably been said to show the facility which 

 the method I have proposed is capable of giving to questions 

 of acknowledged difficulty. I am not aware that it has been 

 before pointed out ; but as I am not at present able to refer to 

 any work on the subject, I cannot speak confidently on this 

 point, [x, a are integral throughout.] 



142 



