348 THE FLORAL WOELD AND GARDEN GUIDE. 



a depth of two feet the temperature usually rises considerably from the middle of 

 April to the middle of July, and is in some seasons subject to many fluctuations ; 

 but during autumn and the early part of winter much of the heat absorbed during 

 summer is retained by the crust, and plants exposed to severe frosts are still warm 

 at their roots, and the atmosphere is so far affected by the radiation of heat from the 

 earth that early frosts are considerably modified in their effects. 



Now the grand object should be to get as much of this heat as possible, and to 

 Iceep it. For this purpose we use frames, the glass coverings of which obstruct the 

 radiation of the earth's heat, and preserve the plants from the severities of the 

 atmospheric temperature. When frost comes we lay on the frames such things as mats, 

 straw, etc., and these still further obstruct the radiation, and prevent the cold 

 winds gaining access to the frames. Everything that can be used to counteract 

 radiation may be turned to account, but there is a good and a bad way of doing it. 

 It so happens — and every gardener should keep the fact in mind — that the atmo- 

 sphere is a tolerably good non-conductor, and a body of air shut up close cools very 

 slowly. It is also to be borne in mind that water is a good conductor of heat, and 

 lience cools quickly, especially at the surface. Suppose we really want (which we 

 never do) to cool down the atmosphere of a frame without taking off the light, the 

 best way to do it would be to throw water on the glass ; the evaporation from this 

 during wind or sunshine would probably soon render the air inside the frame colder 

 than the air without, and at night tlie frost would act upon the wet glass and carry 

 on the cooling process, and if mischief were intended it would be effectual. The 

 rationale of this process is that the heat from the soil and atmosphere of the frame 

 is conducted outwards and dissipated. We learn another lesson from this, namely, 

 to keep the glass, the mats, the^ straw, and whatever else is used for covering, as 

 dry as joossible, and at any time when they are unavoidably wetted they should be 

 taken off and dried at the first opportunity. But we have not yet done. The air 

 is a good non-conductor ; hence, if a mat or tarpaulin can be stretched over a frame 

 and fixed down close at the sides, and the superficies kept at a few inches from the 

 glass— as by laths for instance — there will be a stratum of air between the tar- 

 paulin and the glass, and this will be as good as another thickness, or, to use a 

 homely phrase, will make the frame a coat warmer. In very cold countries, tra- 

 vellers prefer cloaks >to coats ; loose garments are found to be v^armer than tight 

 ones. The reason is that they enclose a considerable body of air, and this being a 

 non-conductor adds to the comfort of the garment. Now, in covering up, loose 

 litter is found very effectual, and, cateris paribus, the looser it is the better. A 

 great heap of dry straw thrown on over a mat will do wonders to keep out frost, 

 because the straw has entangled in it a vast amount of air, which renders it ncn- 

 conducting. Any light dry materi.al, such as waste wool, clippings of hedges, 

 withered tops of chrysanthemums, etc., may be made use of in the frame-ground 

 during hard frost. 



A few more hints may be of service, especially to young gardeners. During 

 frost every plant in a pot — no matter if the hardiest plant known— should have its 

 roots protected. If exposed so that the roots get frozen, death is likely to be the 

 consequence. One of the best materials in which to plunge potted plants, whether 

 indoors or out, is the now famous cocoa-nut fibre refuse. This is never very wet, 

 and never quite dry, and is such a non-conductor that the frost rarely penetrates 

 more than a i&vf inches below the surface, and it may be heaped round the collar of 

 a plant that needs extra protection without any fear of harm, provided it is 

 removed on the return of mild weather. 



Lastly, plants exposed to very low temperatures need not of necessity be ex- 

 posed to light. We have known pits full of geraniums to be buried under heaps of 

 litter for three weeks in complete darkness without taking the least harm. Of 

 course, on the return of mild weather, light should be admitted as soon as possible. 

 In case of plants getting badly frosted, let them thaw slowly, and in the dark. 

 Gardeners sometimes make a rush at the fiie when they find frost in the house, and 

 by getting up too fierce a heat, do more harm than if they had left things alone. 

 Beware of extremes, and aim at making fires burn steady and continuously, rather 

 than at a pace that is likely to roast the inmates of the house. 



