Tull's volume was translated into French by Duhamel, with notes and the record of experiments of his own; from this volume Diderot drew the pith of his article.

Diderot's only merit in the matter--and it is hardly an inconsiderable one in a world of routine--is that he should have been at the pains to seek the newest lights, and above all that he should have urged the value of fresh experiments in agriculture.

Tull was not the safest authority in the world, but it is to be remembered that the shrewd-witted Cobbett thought his ideas on husbandry worth reproducing, seventy years after Diderot had thought them worth compiling into an article.
It was not merely in the details of the practical arts that Diderot wrote from material acquired at second-hand.

The article on the Zend-Avesta is taken from the Annual Register for 1762.

The long series of articles on the history of philosophy is in effect a reproduction of what he found in Bayle, in Deslandes, and in Brucker.