Dr. Young's remarks on the reduction of experiments , &c. 71 
otherwise so easily attainable ; but we must recollect, that at 
least as much good sense is required in applying our mathe- 
matics to objects of a moral nature, as would be sufficient to 
enable us to judge of all their relations without any mathe- 
matics at all : and that a wise government and a brave 
people may rely with much more confidence on the perma- 
nent sources of their prosperity, than the most expert calcu- 
lators have any right to repose in the most ingenious combi- 
nations of accidental causes. 
It is however an important, as well as an interesting 
study, to inquire in what manner the apparent constancy of 
many general results, which are obviously subject to great 
and numerous causes of diversity, may best be explained: 
and we shall soon discover that the combination of a multi- 
tude of independent sources of error, each liable to incessant 
fluctuation, has a natural tendency, derived from their mul- 
tiplicity and independence, to diminish the aggregate varia- 
tion of their joint effect; and that this consideration is suffi- 
cient to illustrate the occurrence, for example, of almost an 
equal number of dead letters every year in a general post 
office, and many other similar circumstances, which, to an 
unprepared mind, seem to wear the appearance of a kind of 
mysterious fatality, and which have sometimes been consi- 
dered, even by those who have investigated the subject with 
more attention, as implying something approaching more 
nearly to constancy in the original causes of the events, than 
there is any just reason for inferring from them. 
This statement may be rendered more intelligible by the 
simple case of supposing an equal large number of black and 
white balls to be thrown into a box, and 100 of them to be 
