144< Botanical, FloricuUiiral, and Arbor icuUural Notices, 



the pit should be warmer than the front. The extreme rapidity 

 of the circulation, already alluded to, is a complete answer to 

 this objection ; but, further, any other arrangement of the circu- 

 lation than that above suggested would be prejudicial, and lead 

 to precisely the opposite results to those intended. In the first 

 place, instead of a great, there would be but a small, difference 

 between the height of the ascending and descending columns, 

 and, consequently, a much slower circulation. In the next place, 

 if the descending flues were at the bottom of the back instead 

 of at the front, and the heated air entered in front, it would 

 immediately rise to the upper part of the pit, and there accumu- 

 late its heat, while the whole surface occupied by the plants 

 would be covered by the coldest air. Moreover, the earth at 

 back being always higher than the front, the coldest air would 

 not flow away to be reheated, but would lie all along the front 

 of the pit, and scarcely circulate at all ; whereas, by the arrange- 

 ment proposed, the coldest air will always descend to be heated, 

 while the influx of warm air, constantly encountering the warmest 

 air which has risen to the top, will beat it down, and mingle it 

 with that below. This is, perhaps, theory, but it is theory 

 based on experience, and I have no hesitation in saying that such 

 would be the effects. 



I am induced to make these remarks, because the objection 

 combated above is very likely to occur to any intelligent person 

 perusing this plan ; and has, in fact, already been made to me 

 by one to whose judgment I should, without good cause to show 

 to the contrary, willingly defer. 



It would prolong a paper already of unseemly length, to 

 point out the manifold convenience of such a pit. Its application 

 to pines and Orchideae, strawberries, &c., is obvious : it may 

 also be employed as a preserving pit ; for, when the apparatus is 

 in full work, the bottom heat alone, with the assistance of a mat, 

 would keep out any frost from a part devoted to geraniums : 

 while, the air-flues of that part being closed, the heating power 

 of the pipe corresponding with them would be expended with 

 accumulated force of circulated air in the forcing-pits which 

 were at work, supplying them with more than their average 

 amount of heat at a season when they most require it. 



Sevenoaks, February 9. 1840. 



Art. XIV. Botanical, FloricuUiiral, and Arboricullural Notices of 

 the Kinds of Plants newly introduced into British Gardens a7id 

 Plantations, or "which have been originated in them ; together with 

 additional hiformation respecting Plants {whether old or neiv) already 

 in Cultivation : the whole intended to serve as a perpetual Supplement 

 to the " Encyclopedia of Plants," the " Horlus Brita?i7iicus," the 



