I^'TR0DUCT10N. 11 



him. It is easy to perceive that a gardener must not only know 

 how to do, but have his reasons for doing, A man who continues 

 to do his annual operations by mere routine, without knowing the 

 foundation or reasons, cannot deviate from the narrow path in 

 which he is confined, when any unexpected accident occurs. 



In the following treatise, we have endeavored to explain these 

 principles, as far as they have been connected with the subjects 

 upon which it treats, and to illustrate them in such a manner as 

 to be easily understood by the general reader. 



The first part of the work we have devoted to the construction 

 of Conservatories, Graperies, Green-houses, Pits, Frames, and 

 every kind of horticultural buildings, giving the diflferent posi- 

 tions and aspects most suitable to each, and the various purposes 

 for which particular structures are best adapted. We have also 

 fully considered the different kinds of materials generally used 

 in thie erection of these buildings, and the respective merits of 

 each. Glass, and its influences on vegetation, are also fully con- 

 sidered and discussed in this part, — a subject which has hith- 

 erto received very little attention from horticultural writers, but 

 is nevertheless one of the most important items connected with 

 exotic gardening. We have given the useful experiments of 

 Mr. Hunt, on Light, and its effects on vegetation and germina- 

 tion, and all other information which we have considered use- 

 ful on this part of our subject. 



The second part embraces the most approved methods of 

 heating horticultural structures, giving the principles of com- 

 bustion and consumption of fuel, the prevention of smoke, and 

 the various volatile products of the coal ; the construction of 

 flues and furnaces ; the different sizes and heating powers 

 of pipes and boilers ; the circulation of water, and the pecu- 

 liar modifications of apparatus suitable for particular struc- 

 tures. We have given a considerable number of illustrations 

 in this part, showing various methods of heating, with all of 

 which we have had extensive practice, and some of them on 

 entirely new principles. The various merits of hot air and 

 hot water are considered on scientific as well as on practical 

 grounds, and each acknowledged for what it is worth. 



The third part may be called the theory and practice of 

 2 



