Marshall and Sons; The Maignen Filter Co.; Messrs. Broadwood and Co. [Illustration: ON THE STUDY OF PHYSICS. XII. ON CRYSTALLINE AND SLATY CLEAVAGE. XIII. ON PARAMAGNETIC AND DIAMAGNETIC FORCES. XIV. PHYSICAL BASIS OF SOLAR CHEMISTRY. [Footnote: From a picturesque point of fact, Pasteur has never, been able to easily.