Ornamentals. 91 



brae, fertilizers, and insecticides. The total number of ex- 

 hibitors, many of whom made exhibits in several different 

 sections, was 175. 



" The first section [which alone we shall discuss] embraced 

 in principle all constructions which are designed to protect 

 plants from the weather, the temperature, light and humidity 

 within being to a certain extent under control. These con- 

 structions are permanent or temporary. The permanent 

 ones are known as greenhouses ; coldframes, hotbeds, and Wood 



. - vs. iron 



other moveable structures are included in the temporary con- houses, 

 structions. The framework of the houses is of wood or iron, 

 or both. There has been much discussion in regard to which 

 material is the better, but by taking a scientific and practical 

 view of the matter all can be summed up in the following 

 sentence : A house should have as much light as possible, 

 and this is obtained by using glass upon as small a frame- 

 work as is consistent with strength. 



'•'In making arrangements for heating a house, its glass 

 surface must be taken into consideration, for the transmission 

 of heat is more rapid through some bodies than through 

 others. If the radiation of heat from glass is taken as a unit, 

 the other substances which are of interest will, under the 

 same conditions, radiate the following amounts of heat : 



Glass 1.0 per cent. 



Wood 0.2 



Iron 35.0 " 



Brick 0.8 



If we assume that the glass covering the house is 30 centi- 

 meters* [nearly twelve inches] wide, the wooden sash-bars 

 three centimeters wide, and the iron ones 5 millimeters'}" [about 

 1-5 inch] wide, it will be seen that the relative amounts of 

 the heat radiated will be 30.6 per cent, for wood frames, and 

 47.5 per cent, for iron frames. 



" In other words, the iron will allow 20 per cent, more heat to 

 be lost than the wood, other conditions being equal. This 

 loss can only be made up by burning a larger amount of fuel 

 and having a greater amount of heating-surface in order to 

 avoid great variations of temperature. Wooden frames are 

 preferable so far as heating is concerned, but they are practi- 



*A centimeter is .3937 inches. *A millimeter is .03937 inches. 



