( 9 ) 
fpeaking, therefore, I fhould have faid, 30 
from o Ts impoflible; but 30 from 100, there 
remains 70. In like manner, the 10 which 
I took from the 9, was in reality 1000: fo 
that in taking 4 from 12, I was really fub- 
tradting 400 from 1200. You now pro- 
ceed to the 7, and, recollecting that one of 
the thoufands was ufed among the hun- 
dreds, you fay 7 from 8, or rather 7000 
from 8000, there remains 1000. 
You will probably think that I have been 
unneceflarily minute in a matter of little 
importance. Nothing is unimportant that 
may throw a (ingle ray of light on the 
threfhold of Science. I am thus explicit on 
the Subtraction of whole numbers, becaufe 
the manner in which it is taught in our 
fchools, feems particularly defigned to pre- 
vent the boys from conceiving any more 
than a mechanical idea of the operation: 
or, if they have any other idea at all, it is 
certainly falfe. They are inftrucled to bor- 
row ten from the next figure in the upper 
line, which ten they afterwards call one and 
reftore it to the next figure in the under 
line. Now, though the refult be the fame, 
whether I increafe the lower, or diminifh 
the upper line, by one, why miflead the 
learner 
