47 8 Mr. wales on the Refolutlon , &c. 
unexhibited in numbers, for want of fome fuch eafy method 
as this, or have done it by means of a long and laborious 
feries of difficult computations ; which, befide the labour 
attending them, are always fubjeft to a variety of errors, 
which cannot he detected, in many cafes, without repeating 
the operation. 
