On risquera toujours de se tromper, lorsque par l'envie de simplifier
on voudra deriver tous les phenomenes de la nature d'une seule et
unique cause."

6. _Pyritologie_ by J. F. Henkel, Paris, Herrissant, 1760, a large
volume in quarto, translated by Holbach. It contains _Flora Saturnisans_
(translated by M. Charas and reviewed by M. Roux), Henkel's
_Opuscules Mineralogiques_ and other treatises. Original editions:
_Pyritologia_, Leipzig, 1725, 1754; _Flora Saturnisans_, Leipzig, 1721;
_De Appropriatione Chymica_, Dresden, 1727, and _De Lapidum origine_,
Dresden, 1734, translated into German, with excellent notes, Dresden,
1744, by M. C. F. Zimmermann, a pupil of M. Henkel. Holbach's translations
seem to have been well received because he writes in this preface:
"Je m'estimerai heureux si mon travail peut contribuer a entretenir
et augmenter le gout universel qu'on a concu pour le saine physique."

7. _Oeuvres metallurgiques_ de M. J. C. Orschall, Paris, Hardy, 1760.
Orschall still accepted the old alchemist tradition but was sound in
practice and was the best authority on copper. Holbach does not attempt
to justify his physics which was that of the preceding century. Orschall
was held in high esteem by Henckel and Stahl.

8. _Recueil des memoires des Academies d'Upsal et de Stockholm_, Paris,
Didot, 1764. These records of experiments made in the Royal Laboratories
of Sweden, founded in 1683 by Charles XI, had already been translated
into German and English. Holbach's translation was made from the German
and Latin. He promises further treatises on Agriculture, Natural History
and Medicine.

9. _Traite du Soufre_ by G. E. Stahl, Paris, Didot, 1766. In speaking of