Nitrogen being acted on was manifestly diamagnetic in relation to common air when both were of the same temperature. Oxygen appears to be magnetic in common air. Hydrogen proved to be clearly and even strongly diamagnetic. Its diamagnetic state shows, in a striking point of view, that gases, like solids, have peculiar and distinctive degrees of diamagnetic force. Carbonic acid gas is diamagnetic in air. Carbonic oxide was carefully freed from carbonic acid before it was used, and it appears to be more diamagnetic than carbonic acid. Nitrous oxide was moderately, but clearly, diamagnetic in air. Olefiant gas was diamagnetic. The coal gas of London is very well diamagnetic, and gives exceedingly good and distinct results. Sulphurous acid gas is diamagnetic in air. Muriatic acid gas was decidedly diamagnetic in air.--_On the Diamagnetic Conditions of Flame and Gases_: Philosophical Magazine, 1847, p. 409. [192] For illustration of this I must refer to my own Memoir, _Researches on the Influence of Magnetism and Voltaic Electricity on Crystallization, and other conditions of matter_, in the Memoirs of the Geological Survey of Great Britain, &c., vol. i. [193] In a work published by Mr. Evan Hopkins, entitled _On the Connexion of Geology with Terrestrial Magnetism_, will be found many valuable practical observations made in this country and the gold and silver districts of America; but the views taken by the author are open to many objections. [194] See a notice by Faraday of Morichini’s Experiments in _Relations of Light to Magnetic Force_--Philosophical Transactions, vol. cxxxvii. p. 15. See also Mr. Christie _On Magnetic Influence in the Solar Rays_--Philosophical Transactions, vol. cvii. p. 219; vol. cxix. p. 379. [195] Sir David Brewster _On Magnetism_; republished from the Encyclopædia Britannica. [196] The whole of the title of Kircher’s book will convey some idea of the subjects embraced:--Athanasii Kircheri Societatis Jesu Magnes, sive de Arte Magneticâ; opus tripartitum, quo Universa Magnetis Natura ejusque in omnibus Scientiis et Artibus usus novâ methodo explicatur: ac præterea e viribus et prodigiosis effectibus Magneticarum aliarumque abditarum Naturæ Motionum in Elementis, Lapidibus, Plantis, Animalibus elucescentium: multa hucusque incognita Naturæ Arcana, per Physica, Medica, Chymica, et Mathematica omnis generis Experimenta recluduntur Editio Tertia: ab ipso Authore recognita emendataque, ac multis novorum Experimentorum Problematibus aucta. Romæ, 1654. [197] The following are the titles of the concluding chapters of Kircher’s book:--_De magnetismo solis et lunæ in maria._ _De magneticâ vi plantarum._ _De insitionis magneticis miraculis._ _De magnetismo virgulæ auriferæ seu divinatoriæ._ _De plantis heliotropiis eorumque magnetismo._ _De magnetismo rerum medicinalium._ _De vi attractivâ potentiæ imaginativæ._ _De magnetismo musicæ._ _De magnetismo amoris._