1822.] Mr. Babbage’s Letter to Sir H. Davy. 387 
of them comprised five or six mathematicians of the highest 
merit, who invesitgated and determined on the formule to be 
employed. The second consisted of seven or eight skilful calcu- 
lators, habituated both to analytical and arithmetical computa- 
tions; these received the formule from the first section, con- 
verted them into numbers, and furnished the proper differences 
to the third, which was constituted of from 60 to 80 persons. 
The most laborious part of the operations devolved upon the 
latter, few of whom were acquainted with more than the first 
rules of arithmetic ; they rendered the calculated results in two 
independent sets, to the second section, for the purpose of veri- 
fication. 
Now it appears that if these or any other tables of similar 
extent, were to be computed by the aid of Mr. Babbage’s engine, 
the number of calculators would be diminished from 96 to 12, 
or even less; so that the tables could be produced at a much 
cheaper rate, and of superior accuracy. 
Another class of tables of the greatest importance is noticed, 
almost the whole of which are capable of being calculated by 
the method of differences ; this includes all astronomical tables 
for determining the positions of the sun or planets. Mr. Bab- 
bage terminates his important communication with the following 
judicious remarks : 
“ Tam aware that the statements contained. in this letter may 
perhaps be viewed as something more than Utopian, and that 
the philosophers of Laputa may be called up to dispute my claim 
to originality. Should such be the case, I hope the resemblance 
will be found to adhere to the nature of the subject rather than 
to the manner in which it has been treated. Conscious, from 
my own experience, of the difficulty of convincing those who 
are but little skilled in mathematical knowledge, of the possibi- 
lity of making a machine which shall perform calculations, I 
was naturally anxious, in introducing it to the public, to appeal 
to the testimony of one so distinguished in the records of Bri- 
tish science. Of the extent to which the machinery whose 
nature I have described may be carried, opinions will necessa- 
rily fluctuate, until experiment shall have finally decided their 
relative value; but of that engine which already exists I think I 
shall be supported, both by yourself and by several scientific 
friends who have examined it, in stating that it performs with 
rapidity and precision all those calculations for which it was 
designed. 
“ Whether I shall construct a larger engine of this kind, and 
bring to perfection the others I have described, will in a great 
measure depend on the nature of the encouragement I may 
receive. 
“ Induced, by a conviction of the great utility of such engines, 
to withdraw for some time my attention from a subject on which 
it has |been engaged during several years, and which possesses 
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