364 INDEX. 



Construction of hot walls. Figure and description of hot wall. Various 

 methods of building hot walls. Trial of hot walls, covered and uncovered. 

 Foreign grapes may be grown on hot walls. Grapes produced on hot walls in 

 England, 2iO 



New method of propelling heated air by means of machinery described by 

 Mr. Marhock in Gardeners' Journal. The air propelled by means of a fan, 246 



PART III. -VENTILATION. 



SECTION I. 



PRINCIPLES OF VENTILATION. 



Attention required from gardeners, &c. Its practical importance. Power 

 of plants to withstand the^changes of climate. Power of vitality possessed 

 by seeds. Power of plants to bear high temperatures. Of bearing delete- 

 rious gases. Effect of winter-forcing on the odor of flowers and on the 

 flavor of fruits, 248 



Whether vegetation purifies the air. Opinions of Priestley of Dr. Dau- 

 beny, of Oxford of Dr. Lindley, of London. Natural adjustment of the 

 atmospherical elements. Atmosphere of cities. Benefits of large trees in 

 the streets. New Haven, the effect of trees in it, 252 



Power of plants to absorb carbonic acid. Gottingen springs. Property of 

 charcoal for absorbing gases. Table of gases and the quantities absorbed by 

 charcoal, 254 



Power of plants to withstand the vicissitudes of temperature. Theories of 

 physiologists. Dalton's chemical philosophy. His theory of the relations of 

 the atmosphere to heat. The properties possessed by caloric, 256 



SECTION II. 



EFFECTS OF VENTILATION. 



Effects of admitting cold air into a hot-house. Moisture carried away. 

 Necessity of keeping the floors damp. Plants unlike animals in respect to 

 ventilation. Ventilation not necessary as regards respiration. Air-tight 

 glass cases for plants, 262 



Knight's experiments on grape vines. The philosophy of this system. 

 Evaporation of moisture on the glass. Contaminating gases in the atmos- 

 phere. Experiments of Drs. Turner and Christison, 264 



The abstraction of moisture in proportion to the rapidity of the motion of the 

 air. Methods of counteracting this loss. Thermometric changes not sat- 

 isfactory rules for the admission of air, 266 



Quantity of moisture contained in the air. Its capacity for moisture. 

 Estimated quantity of air escaped. Estimated quantity of moisture escaping 

 in the air. Lofty plant-houses. Difficulty of managing the atmosphere in 

 them, 269 



SE CTION III. 



METHODS OF VENTILATION. 



Improvements of the present methods of ventilation. Plans adopted to 

 modify the influence of draughts. Motion in the atmosphere. Machinery 

 employed for this purpose. Detection of currents by a common candle. 

 Propriety of a rapid motion disputed, 273 



