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enough to maintain a given temperature, is usually after 

 minute calculation, the quantity which is made use of, 

 and the consequence is, that under adverse circumstances, 

 the apparatus is necessarily worked at its highest pitch ; 

 and I believe that the application of heat in this form, 

 whether it be by means of an hot water apparatus, or by 

 a common flue, is most inimical to the plants submitted 

 thereto. The admission of air, is a point which as far 

 as I am aware, has never been effected in the manner 

 represented in the sketch: it would be thus effected; 

 a series of apertures (f) should be provided at intervals 

 along the front wall, which would externally be closed by 

 small sliding shutters, and would communicate internally 

 with a chamber (<?) formed between the front wall and 

 the side of the tank ; this chamber would also commu- 

 nicate, by a series of openings, (h.) with the interior 

 space above the water in the tank, and from this space, 

 through the covering of the tank, tubes (m), also placed 

 at intervals, would be carried up through the soil, close 

 to the side of the wall ; these tubes should be furnished 

 with caps or valves, so as so admit of the communication 

 being stopped at any time. In applying this to the ad- 

 mission of air, we must not loose sight of a series of ven- 

 tilators, (i), placed in the back wall of the house, which 

 are of precisely the same nature and construction as the 

 apertures (f), already spoken of. I shall have occasion 

 hereafter, to notice the admission of air, but it will be well 

 in this place, to explain the action of the plan proposed 

 for that purpose : when it is judged that a change of the 

 internal volume of air is requisite, the ventilators (i) are 

 to be opened, which admits of a portion of the ratified 

 air to pass off ; the ventilators (f) are also to be opened, 

 and by means of the action of these ventilators on each 

 other, a portion of external air is taken in ; this enters 

 the chamber (#), which is warmed by its contiguity to the 

 tank, and here becomes partially ratified, and rises to the 



