INDEX. 365 



Difficulty of managing the atmosphere in large, dome-shaped houses. 

 Covering necessary. To equalize the temperature. The natural law of 

 equality ineffectual. The slightest cause disturbs the equilibrium of the air. 

 The extreme sensibility of the air. Irregularity of its temperature in hot- 

 houses. The causes of this irregularity. Experiments of Gay Lussac 

 of Rudberg, 275 



A new method of ventilation. Adapted to lean-to houses. Figured and de- 

 scribed. Facility with which this method may be wrought, 277 



Method of ventilating span-roofed houses. Adopted in the new hot-houses 

 at Frogmore. Figures and description of this method, 279 



Methods of airing by the rachet wheels. By springs. Superiority of the 

 former. Necessity of having the machinery for ventilation properly erected. 

 Its liability to get out of repair. Method applauded without merit. Neces- 

 sity of guarding against the applauded inventions of any one, 280 



SECTION IV. 



MANAGEMENT OF THE ATMOSPHERE. 



Atmospheric motion. Admitting large quantities of cold air. The results 

 of this method. Questions arising out of these considerations. The quantity 

 of air to be admitted. Motion affected by various circumstances. The 

 atmosphere of a hot-house influenced by the glazing of the sashes. Effect 

 produced by radiation. Growth of plants in Wardian cases. Deterioration 

 of air by flues, &c., 284 



Method of airing without opening the sashes. Figured and described. 

 This method recommended for houses during cold weather in winter, . . . 288 



Common method of ventilating figured and described. Evils resulting from 

 this method. Action in cold weather, 290 



Contrivance for admitting warmed air into the house over the heating appa- 

 ratus. By a serpentine conductor. Size of the tubes necessary. Radiation 

 of heat from the surface of the flue. The effects of the external air neutral- 

 ized by this method, 292 



The system of ventilation. Its object being to prevent a stagnation in the 

 atmosphere. Evils of this method shown and explained. Mechanical and 

 chemical effects of ventilation, 293 



SECTION V. 



CHEMICAL COMBINATIONS IN THE ATMOSPHERE 

 OF H OT-HOUSE S. 



Nourishment plants ought to receive from the atmosphere. How to receive 

 it. Starch and sugar. Their different properties. Questions arising from 

 considerations of their properties. Experiments on the atmosphere. The 

 importance of oxygen to vegetable life, 296 



Atmosphere from fermenting manure. Quality of heat generated by it. 

 Impregnation of the atmosphere with ammonia. Experiments on the atmos- 

 phere of a green-house with ammoniacal gas, . .299 



Composition of ammonia. Excess of ammonia. Its suffocating influence. 

 Illustrations of its effects. Fumigation of plant-houses and pits with 

 ammonia. The cause of luxuriance in plants. Produced largely from fer- 

 menting manure, &c., 300 



What guides we have to ascertain the various changes in the atmospheric 

 elements. Disagreeable smell on entering a hot-house. The cause, and how 

 to remedy it. The important part played by oxygen in this process. Pro- 

 portion of oxygen necessary to vegetables. Amount contained in atmospheric 

 air and water. Affinity of its elements, 303 



