It is interesting to notice the beginning of relations betwixt Descartes and Pascal, considering the jealousy that afterwards arose betwixt them. There is something of this feeling from the first in the older philosopher, who was now in the forty-fourth year of his age, and in the full zenith of his great reputation. He appears to have been greatly fascinated by Pascal’s peculiar powers; but the men were of too marked individuality of character, and too divergent in intellectual sympathy and personal aspiration, to appreciate each other fully. Pascal’s next achievement was the invention of an arithmetical machine, chiefly prompted by a desire to assist his father in his official duties at Rouen. He has given us no description of this machine from his own pen. In the “Avis” addressed to all whose curiosity was excited by it, he excuses himself from this task by the natural remark that such a description would be useless without entering into a number of technical details unintelligible to the general reader; and that an actual inspection of it, combined with a brief _vivâ voce_ explanation, would be far more satisfactory than any lengthened account in writing. There is an elaborate description, however, of the machine, by Diderot, in the first volume of the ‘Encyclopédie,’ which is reprinted in the collection of Pascal’s scientific works. Pascal’s main difficulties occurred, not in connection with the invention itself, which he seems to have very soon perfected according to his own conception, but with the construction of the instrument after he had mentally worked it out in all its details. These difficulties proved so great, and so many imperfect specimens of the instrument were made, that, in order to secure both his reputation and his interest, he acquired in 1649 a special “privilége du Roi,” which confined the manufacture of the machine to himself, and such workmen as he should employ and sanction. All others, “of whatever quality and condition,” were prohibited from “making it, or causing it to be made, or selling it.” But neither these precautions nor the merits of the invention itself, which were admitted by all competent judges, were of avail to make the instrument a practical success. Many men of mathematical and mechanical genius in different countries have applied themselves to the same task. The celebrated Leibnitz is said to have constructed a machine excelling Pascal’s in ingenuity and power. In our own time, Mr Babbage’s wonderful achievement in the same direction attracted wide attention, and has been lavishly eulogised by Sir David Brewster and others:—