[Footnote 1: Under the head _Androides_ in the Edinburgh Encyclopædia may be found a full account of the principle automata of ancient and modern times.] But if these machines were ingenious, what shall we think of the calculating machine of Mr. Babbage? What shall we think of an engine of wood and metal which can not only compute astronomical and navigation tables to any given extent, but render the exactitude of its operations mathematically certain through its power of correcting its possible errors? What shall we think of a machine which can not only accomplish all this, but actually print off its elaborate results, when obtained, without the slightest intervention of the intellect of man? It will, perhaps, be said, in reply, that a machine such as we have described is altogether above comparison with the Chess-Player of Maelzel. By no means--it is altogether beneath it--that is to say provided we assume (what should never for a moment be assumed) that the Chess-Player is a _pure machine_, and performs its operations without any immediate human agency. Arithmetical or algebraical calculations are, from their very nature, fixed and determinate. Certain _data_ being given, certain results necessarily and inevitably follow. These results have dependence upon nothing, and are influenced by nothing but the _data_ originally given. And the question to be solved proceeds, or should proceed, to its final determination, by a succession of unerring steps liable to no change, and subject to no modification. This being the case, we can without difficulty conceive the _possibility_ of so arranging a piece of mechanism, that upon starting it in accordance with the _data_ of the question to be solved, it should continue its movements regularly, progressively, and undeviatingly towards the required solution, since these movements, however complex, are never imagined to be otherwise than finite and determinate. But the case is widely different with the Chess-Player. With him there is no determinate progression. No one move in chess necessarily follows upon any one other. From no particular disposition of the men at one period of a game can we predicate their disposition at a different period. Let us place the _first move_ in a game of chess, in juxta-position with the _data_ of an algebraical question, and their great difference will be immediately perceived. From the latter--from the _data_--the second step of the question, dependent thereupon, inevitably follows. It is modelled by the _data_. It must be _thus_ and not otherwise. But from the first move in the game of chess no especial second move follows of necessity. In the algebraical question, as it proceeds towards solution, the _certainty_ of its operations remains altogether unimpaired. The second step having been a consequence of the _data_, the third step is equally a consequence of the second, the fourth of the third, the fifth of the fourth, and so on, _and not possibly otherwise_, to the end.