498 
PROFESSOR JEVONS ON THE MECHANICAL 
4. As early as the 17th century we find that machinery was made to perform actual 
arithmetical calculation. The arithmetical machine of Pascal was constructed in the 
years 1642-45, and was an invention worthy of that great genius. Into the peculiarities 
of the machines subsequently proposed or constructed by the Marquis of Worcester, 
Sir Samuel Morland, Leibnitz, Gersten, Scheutz, Donkin, and others we need not 
inquire ; but it is worthy of notice that M. Thomas, of Colmar, has recently manufac- 
tured an arithmetical machine so perfect in construction and so moderate in cost, that 
it is frequently employed with profit in mercantile, engineering, and other calculations. 
5. It was reserved for the profound genius of Mr. Babbage to make the greatest 
advance in mechanical calculation, by embodying in a machine the principles of the 
calculus of differences. Automatic machinery thus became capable of computing the 
most complicated mathematical tables*; and in his subsequent design for an Analytical 
Engine Mr. Babbage has shown that material machinery is capable, in theory at least, 
of rivalling the labours of the most practised mathematicians in all branches of their 
science. Mind thus seems able to impress some of its highest attributes upon matter, 
and to create its own rival in the wheels and levers of an insensible machine. 
6. It is highly remarkable that when we turn to the kindred science of logic we meet 
with no real mechanical aids or devices. Logical works abound, it is true, with meta- 
phorical expressions implying a consciousness that our reasoning powers require such 
assistance, even in the most abstract operations of thought. In or before the 15th 
century the logical works of the greatest logician came to be commonly known as the 
Organon or Instrument , and, for several centuries, logic itself was defined as Ars instru- 
mental is dirigens mentem nostram in cognitionem omnium intelligibilium. 
When Francis Bacon exposed the futility of the ancient deductive logic, he still held 
that the mind is helpless without some mechanical rule, and in the second aphorism of 
his ‘New Instrument’ he thus strikingly asserts the need: — 
Nee manus nuda , nee Intellectus sibi gjermissus, multum valet ; Instrumentis et aux- 
iliis res perjicitur ; guibus oggus est, non minus ad intellectum , guam ad manum. Atgue 
ut instrumenta manus motum aut cient , aut regunt ; ita et Instrumenta mentis , Intel- 
lectid aut suggerunt aut cavent , 
7. In all such expressions, however, the word Instrument is used metaphorically to 
denote an invariable formula or rule of words, or system of procedure. Even when 
Raymond Lully put forth his futile scheme of a mechanical syllogistic, the mechanical 
apparatus consisted of nothing but written diagrams. It is rarely indeed that any invention 
is made without some anticipation being sooner or later discovered ; but up to the present 
time I am totally unaware of even a single previous attempt to devise or construct a machine 
which should perform the operations of logical inference f; and it is only I believe in the 
satirical writings of Swift that an allusion to an actual reasoning machine is to be found^. 
* See Companion to the Almanack for 1866, p. 5. f See note at the end of this paper, p. 518. 
+ In the recent Life of Sir W. Hamilton, by Professor Veitch, is given an account and figure of a wooden 
instrument employed by Sir W. Hamilton in his logical lectures to represent the comparative extent and intent 
