CHAPTER IV. 



HEATING AS APPLIED TO HORTICULTURAL ERECTIONS. 



§ 1. — PRELIMINARY REMARKS. 



Waving consideration of the theories which 

 philosophers have advanced regarding the 

 nature and properties of heat, let it be our 

 task to consider its application to the pur- 

 poses of horticulture, and endeavour to 

 elucidate its use, on correct principles, in 

 the various departments of that science. 



As man advanced in civilisation and 

 luxury, artificial heat became necessary 

 to him, first for warming his dwelling, 

 and afterwards to produce those exotic 

 rarities for his table which his native 

 climate had denied him. For this latter 

 purpose heat has been employed for ages ; 

 but it must be acknowledged that, until 

 within a very recent date, it has been in 

 every instance applied upon the most 

 unphilosophical principles imaginable, 

 not only in respect of the production of 

 an unhealthy atmosphere and uncertain 

 temperature, but also as regards the con- 

 sumption of an unnecessary quantity of 

 fuel. Nor are the opposite results all the 

 advantages which modern improvement 

 has made in this case : — economy, neat- 

 ness, and order have taken the place of 

 filth, waste, and confusion. As healthy 

 an atmosphere is now produced in all 

 well-regulated hothouses as there is in 

 the open air ; and instead of difficulties 

 presenting themselves in heating a mode- 

 rate-sized pine-stove, we find none, now, 

 in heating an entire garden, whatever 

 may be its extent. 



In preparing these pages, we have con- 

 sulted every work of merit in which 

 heating, so far as regards our present 

 subject, is treated of, and have examined 

 upwards of one hundred and twenty dif- 

 ferent modes of applying heat by combus- 



tion alone, exclusive of the different 

 methods of obtaining it by the fermenta- 

 tion of various substances. Many of 

 these methods are absurd, as may well 

 be supposed; and among these are not 

 a few of very recent date, and of high 

 pretensions. We have no interest what- 

 ever in one mode of heating more than 

 another ; and having had opportunities, 

 not only of seeing most of them in opera- 

 tion during the last forty years, but also 

 of practical experience both in the erec- 

 tion and working of many of them, w T e think 

 we have a right to express our opinion of 

 them unbiassed and freely. We thought 

 at first of selecting plans only of those 

 which we considered of greatest utility ; 

 but as there is at present so great a 

 diversity of opinion amongst gardeners, 

 and so much self-interest among trades- 

 men, with no small amount of adherence 

 to the old fashions amongst some of the 

 old-school practitioners, it has seemed 

 better, as it is more fair, to give condensed 

 descriptions, accompanied by illustra- 

 tions, of all the various methods worthy 

 of notice, offering our opinion on their 

 merits or defects en passant. This ar- 

 rangement may have its advantages, 

 as we have more than once seen some 

 very old modes of heating brought out 

 as new, which it may expose, while it 

 may also assist in the creation of ideas, 

 and important improvements may yet be 

 brought out of plans that have been long- 

 considered obsolete. In a work of this 

 kind we consider it as much our duty to 

 point out the defects as to recommend 

 the merits of any particular system or 

 subject under our consideration. 



The most primitive mode of heating 

 was that employed by the Dutch, which 



