In all the chief departments of industry there are plates good enough to serve for practical specifications and working drawings.

It has often been told how Diderot himself used to visit the workshops, to watch the men at work, to put a thousand questions, to sit down at the loom, to have the machine pulled to pieces and set together again before his eyes, to slave like any apprentice, and to do bad work, in order, as he says, to be able to instruct others how to do good work.

That was no movement of empty rhetoric which made him cry out for the Encyclopaedia to become a sanctuary in which human knowledge might find shelter against time and revolutions.

He actually took the pains to make it a complete storehouse of the arts, so perfect in detail that they could be at once reconstructed after a deluge in which everything had perished save a single copy of the Encyclopaedia.
Such details, said D'Alembert, will perhaps seem extremely out of place to certain scholars, for whom a long dissertation on the cookery or the hair-dressing of the ancients, or on the site of a ruined hamlet, or on the baptismal name of some obscure writer of the tenth century, would be vastly interesting and precious.

He suggests that details of economy, and of arts and trades, have as good a right to a place as the scholastic philosophy, or some system of rhetoric still in use, or the mysteries of heraldry.