ts were made; the most important being that invented by
Napier of Merchiston, the inventor of logarithms, commonly called
Napier's bones, consisting of a number of rods divided into ten equal
squares and numbered, so that the whole when placed together formed the
common multiplication table. By these means various operations in
multiplication and division were performed. Sir Samuel Morland,
Gunter, and Lamb introduced other contrivances, applicable to
trigonometry; Gunter's scale being still in common use. The
calculating machines of Gersten and Pascal were of a different kind,
working out arithmetical calculations by means of trains of wheels and
other arrangements; and that contrived by Lord Stanhope for the purpose
of verifying his calculations with respect to the National Debt was of
like character. But none of these will bear for a moment to be
compared with the machine designed by Mr. Babbage for performing
arithmetical calculations and mathematical analyses, as well as for
recording the calculations when made, thereby getting rid entirely of
individual error in the operations of calculation, transcription, and
printing.

The French government, in their desire to promote the extension of the
decimal system, had ordered the construction of logarithmical tables of
vast extent; but the great labour and expense involved in the
undertaking prevented the design from being carried out. It was
reserved for Mr. Babbage to develope the idea by means of a machine
which he called the Difference Engine. This machine is of so
complicated a character that it would be impossible for us to give any
intelligible description of it in words. Although Dr. Lardner was
unrivalled in the art of describing mechanism, he occupied twenty-five
pages of the 'Edinburgh Review' (vol.59) in endeavouring to describe
its action, and there were several features in it which he gave up as
hopeless. Some parts of the apparatus and modes of action are indeed
extraordinary and perhaps none more so than that for ensuring accuracy
in the calculated results,--the machine actually correcting itself, and
rubbing itself back into accuracy, when the disposition to err occurs,
by the friction of the adjacent machinery! When an error is made, the
wheels become locked and refuse to proceed; thus the machine must go
rightly or not at all,--an arrangement as nearly resembling volition as
anything that brass and steel are likely to accomplish.

This intri