August 20, 1872. ] 



JOTJBNAL OP HOETICULTUEE AND COTTAGE GAEDENEE. 



167 



and a figure-8 bed of Abutilcm Thornpsoni and Iresine Lindeni, 

 edged with Lobelia, with Stachys lanata next the grass. 



We had last year occasion to notice the beautiful order in 

 •which both the beds and turf are kept ; and this year, under 

 more disadvantageous circumstances as regards the former, 

 owing to the frequent heavy rains we have had this summer, 

 nothing can be more trim than the appearance of the beds, 

 from which dead leaves and withered flowers are evidently 

 carefully removed wherever needful, thus greatly enhancing 

 their beauty ; while to keep the grass so short and velvety as it 

 is, must have involved careful attention and frequent cutting. 

 (To be continued.) 



HEATING BY HOT WATER AND HOT AIE. 



As your reporter of the horticultural structures, heating 

 apparatus, and other exhibits of a like nature at Birmingham, 

 allow me to answer the remarks made by Mr. Housman on 

 -ihe subject of heating by hot air, pages 110 and 111. Mr. 

 Housman, apparently, is not well pleased that I did not make 

 a more favourable notice of his stove and model in Stand 45. 

 My reason for using the expression, "that no system of hot 

 air has yet been invented in which all the heat has been ex- 

 tracted from the fuel in a stove and given up to the buildings 

 to be heated," was because Mr. Housman, in a short paper 

 explaining his system of hot air, seemed to claim its superiority 

 over hot water, on the ground that it was more economical to 

 heat ah' by direct action of the stove than to convey heat to 

 houses by means of hot water. No doubt it was a truism, and 

 liable to the remark made by Mr. Housman, " That 's so, as a 

 Yankee would say." What I wished to infer was, " that the 

 relative merits of two heating apparatuses almost entirely 

 depend on the amount of heat extracted from the fuel con- 

 sumed, and that no hot-air system as yet invented is superior 

 to hot water, unless the chimney is also utilised as a flue." I 

 send Mr. Housman's paper for insertion in fuU 



Bemarjcs on a Plan for Heating and Ventilating Horticultural 

 Structures by Hot Air, 

 Except in the case of small detached horticultural structures, 

 for the heating of which the value and economy of stoves is 

 recognised by many practical horticultural writers, the applica- 

 tion of hot water for the production of an artificial climate 

 appears to be accepted as the most desirable means of obtaining 

 that end. For the causes of this acceptation we have not far to 

 seek. The mobility of the heat supplied, as contrasted with the 

 fixedness of heat supplied from the ordinary flue or stove ; the 

 capacity for an indefinite extension of heating surface at any 

 required poiut ; the absolute security from burning of the air ; 

 and the delivery of the heat at a low velocity, and at a low tem- 

 perature from a widely-extended surface, afford good reason for 

 the popular acceptance of hot-water apparatus. On the other 

 hand, the crudeness of the idea of employing one fluid as the 

 medium of conveying heat to another, which, up to a certain 

 point, it is confessed is more advantageously heated directly; 

 the cumbrousness of the apparatus, and in many cases the un- 

 sightliness of it ; the necessity (if a series of houses are to be 

 interchangeable) that each house shall be supplied with the 

 maxium amount of heating surface the greater part of which 

 generally lies idle in reserve ; and the absence of any accurate 

 provision for incessant supplies of fresh warmed air for winter 

 ventilation, indicate that much yet remains to be done in per- 

 fecting the mode of heating and ventilating our horticultural 

 structures. 



The exhibitor of the stove and. model, No. 874, Stand No. 45, 

 has taken as his leading principles the following points : — 



1st. — That a house intended to maintain an artificial climate 

 must be as perfect in structure as possible. 



2nd. — That an incessant influx of warmed fresh air must 

 be provided for, and that the corresponding efflux (which 

 represents loss of heat) shall be from the coldest air in the 

 house. 



3rd. — That the arrangements for affording this fresh-air 

 supply shall be under absolute control, and not dependant 

 upon imperfect glazing, or on " a trifle of top air left on." 



_ 4th. — That it is impossible that arrangements for ventila- 

 tion fitted for summer weather can be rightly applicable to 

 the reversed conditions of atmosphere existing in winter. 



5th. — That in consecutive houses heated air can be dis- 

 tributed and apportioned with greater facility than heated 

 water can. 

 In the model exhibited, the heat-supply ascends from a hot- 

 air chamber, being driven from thence by pressure of the outer 

 ah- — that is to say, entirely by the outer air, and not by currents 

 from the interior, as in Polmaise. 



The source of heat preferred by the exhibitor is the well- 

 known brick Arnott's stove, with its heating surface widely 



extended on the principle of the Gurney stove ; and so placed 

 in a shaft as to be kept at a low temperature by the velocity of 

 the current passing over it. Increase of velocity of current is 

 equivalent to an increased heating surface of lowered tem- 

 perature. 



The current of heated air, passing along an air flue, is delivered 

 into the houses in varied quantities, through gratings regulated 

 by hit-and-miss valves. This current can be made to pass over 

 water, at any point of its course. 



By means of a similar hit-and-miss arrangement, a series of 

 apertures on the level of the floor are opened to the outer air, 

 to such an extent as will afford passages of efflux equal to the 

 passages of influx through the gratings in the floor. 



In houses of perfect structure, the opening of the communica- 

 tions with the outer ah' will absolutely regulate the influxes 

 from the hot-air chamber. If opened to the fullest extent, the 

 supply of fresh air will be copious and of a low temperature ; if 

 the means of exit are scant, the supply will be scant but of a 

 high temperature. 



A fall of the temperature of the outer air, or a rise of the tem- 

 perature of the inner air, increases the velocity of circulation 

 in the house. In Polmaise arrangements the circulation slackens 

 as the house becomes hotter; so, too, in closed houses heated by 

 hot water, the motion of the air becomes more sluggish as tho 

 house becomes hotter. 



From the model exhibited it will appear how the air ejected 

 from the hotter houses is utilised by passing it through cooler 

 ones ; also how, when the appliances for summer ventilation are 

 called into play, and top ah' is given, the upcast shafts in the 

 wall become downcast, and deliver cool air on the floor level, 

 which can be mingled at will with supplies f :( m the floor grat- 

 ings, warmed and moistened, or otherwise. 



. The model, as arranged, represents a series of three houses — 

 the one nearest the hot-air chamber being a late vinery, the one 

 farthest from it an early vinery, and the centre one an inter- 

 mediate house. The end houses communicate with the centre 

 one by sluices at the bottom of the doors or partitions. All 

 openings to the outer ah' in the end houses are closed. In the 

 centre house the hot-air gratings are entirely closed, and a 

 sufficient quantity of passages to the outer air are opened. As 

 much 'dry warm air as may be needful being admitted through 

 the gratings of the first house, it circulates, and, having no other 

 means of exit, escapes through the sluices into the cooler house 

 in the centre. Here it again ascends, and circulates, expelling 

 a corresponding volume to the outer air. The remaining part 

 of the current in the warm-air flue passes on under the closed 

 gratings of the centre house, absorbing moisture from troughs 

 of water placed in its course, and is discharged in the early 

 house, there ascending and circulating, and then r>assing into 

 the centre house, and from thence to the outer air. 



I do not agree to Mr. Housman's remarks " on the crudeness 

 of the idea of employing one fluid as the medium of conveying 

 heat to another." Water is such an infinitely better conductor 

 of heat than ah-, and has the power of storing up so mucli 

 heat, that with the advantages it possesses, which Mr. Hous- 

 man has so well enumerated,' and which I need not repeat, 

 there is no crudeness in the idea, but scientific knowledge, in 

 utilising water for the conveyance of heat, especially where the 

 heat is wanted at a comparatively low temperature, so that 

 for plant structures hot water will assuredly always hold its 

 own. I will, however, examine his five principles. 



First is a truism. In No. 2, the word which represents 

 loss of heat (casually introduced in brackets), is the really 

 weak point in his plan. If the influx of heated ah- is made to 

 depend on the efflux of cold air, and as Mr. Housman speaks of 

 the heat being extracted from the Gurney stove by means of 

 the velocity of the currents, there must be a proportionably 

 rapid loss of heat through the air, which passes according to 

 his theory into the outer air. 



No. 3 I will also agree to, but I totally dissent with regard 

 to No. 4, as a house may be constructed with a system of ven- 

 tilation equally adapted both for summer and winter. 



No. 5 I also deny the truth of, because there is nothing so 

 easy or so certain as to apportion the quantity of piping to the 

 size of the houses and temperature required. Practically 

 speaking, with any hot-air system where the heated air is re- 

 gulated by outer air, the quantity of air supplied is very much 

 dependant on the force and direction of the wind, and nothing 

 would prevent cold currents of outer air forcing themselves 

 into the house through the series of apertures Mr. Housman 

 speaks of on the level of the floor, if there were any pressure of 

 wind, especially if it happened to blow directly upon the house 

 in the position where the openings were. 



The source of heat is the brick Arnott's stove with its 

 heating surface extended by means of gills of iron. Now the 

 fire has to heat the inside bricks, then to heat the iron, which 



