CONTENTS. x j 



It is not the Tit/ionic Ray. Maximum of Decomposing Action for Carbonic Acid and Carbonaceous 

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

 coincides therewith Page 72 



CHAPTER IX. 



THEORY OF THE ABSORPTION OP THE TITHONIC RAYS AND LIGHT. 



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

 Absorptive Action of Chlorine and Hydrogen. Detithonization of the Ray and Tithonizalion 

 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 Chrysotype. Case of Bichromate of Potash. Laws deduced. Control of Optical Forces over 

 Chemical Effects. 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 Brill- 

 iancy 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 MOVEMENTS OF PLANTS UNDER THE INFLUENCE OF THE DIFFERENT RAYS OF LIGHT. 



Movements described. Produced by Artificial Light. Experiment of Dr. Poggioli. Experiments 

 of Dr. Gardner, M. Payer, and a Committee of the French Academy. Movement takes place in 

 two Directions, 1st, towards the Light ; 2d, Laterally. The first Motion is produced by the Indigo 

 Ray. Tables of Direct and Lateral Movement. Lateral Motion commences in the Yellow. 

 Connexion between the Colour of the Sky and the Vertical Position of Stems. 



The Roots recede from the Violet Light. Movement begins in the Violet. Lateral Flexure of the 

 Roots. It is towards the Red. It commences with the Yellow Ray 99 



CHAPTER XIII. 



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. Oxydating 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 differ- 

 ent coloured Rays. Effects of these Radiant Principles on the Lower Tribes of Animals. Cen- 

 tralization 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 103 



