12 INTRODUCTION. 



ventilation, including some valuable investigations of the p/iys- 

 iological effects of the atmosphere, under different circumstances, 

 and at different temperatures. Many of our remarks nave 

 assumed a greater length than we originally intended, and if 

 some appear repetitionary, this is in order to avoid, as much 

 as possible, all strictly scientific technicalities and abstruse 

 reasoning, whereby the minds of practical men are frequently 

 unable to understand fully the end to which you direct them. 

 We have added a section on the protection of horticultural 

 structures in severe weather, — a subject which is worthy of 

 much consideration. 



I may observe, that, in pointing out and freely comment- 

 ing on principles and practices which are erroneous, but which 

 have been practised and promulgated by others, it is under the 

 impression that such errors, carrying with them, in general, 

 some plausibility, have led, and may still lead, others to fall into 

 similar mistakes. However invidious, therefore, be the task of 

 pointing out these errors, it would be manifestly impossible to 

 write on this subject without noticing them, and, if possible, 

 pointing out the difference between right and wrong. This is the 

 only apology which can be offered for the freedom with which 

 some of the opinions and methods of others have been com- 

 mented on in the various parts of this treatise. We have, how- 

 ever, expatiated on them candidly, and in the true spirit of 

 inquiry, pointing out the applicability of their principles and the 

 utility of their practice. 



The different parts of the subject have been arranged under 

 different heads, as far as has been practicable, in order that any 

 of the different parts may be pursued intelligibly and clearly. 

 In extenuation of any errors which may be found, we hope it 

 will be considered that many of the points treatei on are 

 entirely new, and as yet undeveloped ; that no comprehensive 

 view of the principles of exotic culture has yet been given. 

 But we must not be understood to offer excuses for any errors 

 other than those that are embraced by this extenuating clause 

 which will be acknowledged if rectified in the true spirit of 

 philosophical inquiry. 



