CONTENTS. 



Mellom's Researches on the Distribution of Heat in Perfect Prismatic Spectra. Apparent Identity of Light 

 and Heat. 



Distribution of Chemical Force in the Interference Spectrum. Comparison of the Fixed Lines in the Pris- 

 matic and Interference Spectrum. Mode of Defining Chemical Effects by Wave-lengths or by Times of 

 Vibration. Impression on Bromide of Silver. On Chloride of Silver. Total Change in the Distribution 

 of Heat in the Interference Spectrum . . Page 52 



CHAPTER VI. 



EXPERIMENTS PROVING THAT IT IS IN THE YELLOW REGION OF THE SPECTRUM THAT THE REDUCTION 

 OF CARBONIC ACID BY THE LEAVES OF PLANTS TAKES PLACE. 



Several Imponderable Principles in the Sunbeam. Sennebier's Experiments to determine to which of these 

 the Effect is due. Experiments of Morren and Daubeny. Defects of the Mode of operating with Absor- 

 bent Media and Glasses. 



Decomposition of Carbonic Acid in the Prismatic Spectrum. Process of conducting the Experiment. It. is 

 in the Yellow Region that the Decomposition takes place. No Gas is evolved in the Violet . . 61 



CHAPTER VII. 



ON THE VARIOUS IMPONDERABLE AGENTS EXISTING IN THE DIFFERENT REGIONS OF THE SPECTRUM. 



Different Agents existing in the Spectrum. Description of the Tithonic Rays. Their Name. Physical 

 Independence of Heat. Of the Chemical Rays. Their Constant Association with Light. Detithonizing 

 Action of Yellow Solutions. Argument for their Independence. Other Invisible Principles in the Sun- 

 beam, such as the Phosphoric Rays. Examination of the Theory of M. Becquerel . . . .65 



CHAPTER VIII. 



IT IS YELLOW LIGHT WHICH CONTROLS THE PROCESS OF DIGESTION IN PLANTS. 



Examination as to which of the Principles mentioned in the preceding Chapter is engaged in the Decompo- 

 sition of Carbonic Acid. It is not Radiant Heat. Melloni on the Ideal Coloration of Heat. Analogies 

 in the Case of Light. Herschel's Results. 



It is not the Tithonic Ray. Maximum of Decomposing Action for Carbonic Acid and Carbonaceous Com- 

 pounds, like the Retina, is in the Yellow Ray. Hence the Maximum of Visible Illumination coincides 

 therewith 72 



CHAPTER IX. 



THEORY OF THE ABSORPTION OF THE TITHONIC RAYS AND LIGHT. 



Estimate of the Extent and Power of the Solar Radiations. Influence still exists in the Moonbeams. Ab- 

 sorptive Action of Chlorine and Hydrogen. Detithonization of the Ray and Tithonization of the Gaseous 

 Mixture. Curve and Law. Deductions as to Latent Light and Definite Action. Functions discharged 

 by the Chlorine and Hydrogen respectively ........... 76 



CHAPTER X. 



THEORY OF IDEAL COLORATION. 



Former Observations on Colours in the Chemical Rays. Nomenclature derived from it. Case of the Chry- 

 sotype. Case of Bichromate of Potash. Laws deduced. Control of Optical Forces over Chemical Ef- 

 fects. Application to Spectrum Stains. Herschel's Law for Light. Explanation of Variable Effects in 

 Films of different Thickness. Mode of Action of the Tithonic Rays . . . . . .84 



CHAPTER XI. 



ON THE MODE OF ACTION OF LIGHT IN DIRECTING THE DIGESTION OF PLANTS. 



Connexion between Absorption and Chemical Action. Radiant Matter is absorbed in producing different 

 Effects. Reappearance of the Force expended. Laws of Preliminary Absorption and Definite Action 

 observed by Plants. Increased Rapidity of Vegetation implies increased Brilliancy of the Incident Light. 

 The Sun probably a Periodic Star. Description of the Mode of Action of Light and Radiant Heat on 

 Leaves ............ ... 91 



CHAPTER XII. 



ON THE NERVOUS AGENT OF PLANTS. 



Subdivisions of Nervous Mechanism in Animals. Excessive Rapidity of Motion arising in these Nervous 

 Actions. Plants constructed on a Surface-type. Oxidating Processes replaced in them by the Application 

 of Radiant Heat. Difference of Action on the Upper and Under Face of the Leaf. Light applied to one, 

 and Heat to the other Face. Specific Effects produced by the different coloured Rays. Effects of these 

 Radiant Principles on the Lower Tribes of Animals. Centralization of Apparatus for different Functions. 

 Analogies between Nervous Action in Animals and Imponderable Agency in Plants. Vegetables are 

 the Representatives of the Resultant Action of the Ethereal Agents on Ponderable Matter. Conclusion 99 



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