Letter III
The Manufacture of Soda from Culinary Salt; its importance in the Arts and in Commerce. Glass—Soap—Sulphuric Acid. Silver Refining. Bleaching. TRADE IN SULPHUR.
Letter IV
Connection of Theory with Practice. Employment of MAGNETISM as a moving power—its impracticability. Relation of Coals and Zinc as economic sources of Force. Manufacture of Beet-root Sugar—its impolicy. Gas for illumination.