General Notices. 635 



which would melt _ platina, without producing any effect when the concen- 

 tration takes place in air or water. 



The enormous differences produced in the rate of cooling and transmission 

 by change of surface, as shown in Sir John Leslie's and other experiments, 

 prove beyond question that radiation is the great and important channel by 

 which interchanges of heat take place, and that when it is proposed to sub- 

 stitute for this the carrying power of the air, we adopt a feeble, difficult, cir- 

 cuitous mode of effecting a purpose which will aecomplish itself rapidly and 

 spontaneously, by placing the objects, so to speak, in sight of each other. 

 There is the further advantage, before alluded to, that by radiant heat we 

 communicate heat only ; whereas, by using air, we introduce a new set of con- 

 ditions in regard to moisture. With radiant heat it may, indeed, be requisite 

 to supply moisture, which, when necessary, is easily done ; but with air as the 

 carrier, air, therefore, in constant change, we employ a vehicle whose relations 

 to moisture are extremely difficult to maintain in exactly the proper state. 

 Air, warmed and unsupphed with moisture, is a very sponge, and exerts an un- 

 limited drying influence upon all fluids presented to it ; and air, if warmed and 

 fully saturated, becomes a wet sponge, which will deposit moisture on all 

 bodies at an inferior temperature with which it comes in contact. The fact 

 is, that air is a very efficient cooler or warmer, if it be allowed freely to attract 

 moisture in the one case or to deposit it in the other ; but as we do not 

 always require to do these, or not, at least, in the proportions which might 

 suit the capacity of the air for absorbing or retaining moisture, it is better, I 

 think, to warm by means which are more independent. {Gard. Chron., 

 vol. i p. 212.) 



Boiler Furnaces. — Mr. Ainger recommends combustion within slowly-con- 

 ducting materials, radiation to the largest possible quantity of surface, and 

 avoidance of circuitous flues. {Ibid., p. 684.) 



Laying Hot-water Pipes in Troughs of Water, as at Mrs. Lawrence's and 

 Mr. Green's, is strongly recommended. (Ibid., p. 597.) 



Glazing Hothouses. — The exclusion of water and the prevention of break- 

 age depend much on the laps touching in every part, so as to admit no mois- 

 ture between ; such moisture being driven into the house by high winds, and 

 expanding and breaking the glass during frost. {Ibid., p. 646.) 



Old Putty softened. — Old putty may be softened by rubbing it with soft 

 soap, and allowing it to remain for a few hours. {Ibid., p. 685.) To remove 

 old putty, the glaziers pass a warm iron a few times over it. {Ibid., p. 613.) 



A Pit for luintering Plants should have the bottom dry, by its being raised 

 12 or 18 inches above the adjoining surface, besides should be so constructed 

 as to exclude frost, and the aspect should be to the north. If it faces the 

 south, the air within it is apt to become heated by the sun, and thus the 

 plants are stimulated into temporary growth at unpropitious seasons. 



The necessity for a winter-house being dry, seems [to arise out of the 

 nature of vegetation, which, being entirely passive, cannot resist the influence 

 of surrounding media. If the air or soil is damp, plants exposed to them 

 must absorb that moisture : but, from the lowness of the temperature of a 

 winter-house, their powers of digestion and assimilation are torpid, and there- 

 fore the water they receive, instead of becoming incorporated with their 

 system, stagnates in their cells and cavities, where it becomes putrid ; and, as 

 soon as this takes place, the evil extends with rapidity, causing both branches 

 and stems to become rotten ; for decay in plants is always contagious, and 

 will spread through all the parts with which it is in contact, until the reno- 

 vated forces of vegetation restore the equilibrium of chemical constituents, 

 and thus arrest contagion." {Ibid., p. 659.} 



A Friiit'Room. — The principles which ought to guide the designer are, 

 darkness, a low and steady temperature, dryness to a certain point, for 

 apples are found to keep best in a rather damp atmosphere, and exclusion 

 of the external ^air. If the light of the sun strikes upon a plant, the latter 

 immediately parts with its moisture by perspiration, in proportion to the 



