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Commercial Gardening 



of 4-in. piping required to heat 1000 cub. ft. of air per minute from 

 45 to 90 F., the temperature of the pipes being 200 F. 



If a house containing 10,000 cub. ft. of air is to be kept at a tempera- 

 ture of 70 F., the external air being at 32 (freezing-point), the amount of 

 piping required is found thus: Go down the column under 70 and find 

 the figures opposite the given temperature of the external air, that is 32. 

 The figures 164 stand opposite this and beneath the 70. Multiply 164 

 ~by 10, and the result 1640 represents the number of feet of 4-in piping- 

 according to Hood's method. This, however, will scarcely do for horti- 

 cultural purposes, as no one would dream of heating his hot-water pipes 

 up to 200 F. only twelve degrees below boiling-point. And, moreover, 

 the length of piping cannot be varied at will, in accordance with the 

 fluctuations of the external air. The quantity of piping is really regulated 

 according to whether a structure is to be treated as a greenhouse or a 

 hothouse, the latter requiring about twice as much piping as the former. 

 Taking a house 100 ft. long, 12 ft. wide, and 8 ft. high to the ridge board 

 with walls to the eaves 3 ft. high, we get a house with about 9000 ft. 

 cubic capacity. If used as a greenhouse with a minimum winter tempera- 

 ture of 45 F., about 500 ft. of 4-in. piping will be sufficient in the usual 

 way, but an extra 200 ft., making 700 ft. altogether, would maintain a 

 temperature at a minimum of 50 to 55. In a similar house, 1000 to 

 1200 ft. of 4-in. piping would maintain a stove temperature during the 

 winter months without heating the pipes to more than 100 F. 



Heating horticultural structures by steam is practised in America, 

 where climatic conditions are different, but it is not likely to be adopted 

 in Britain. 



Fuel. This is one of the greatest expenses to the commercial grower 

 with extensive ranges of glass, and prices of coal and coke have increased 

 enormously during the past twenty years, while the price of produce has 

 fallen just as much; and labour has also increased. The two principal 

 fuels used are coke and anthracite coal some growers preferring one, some 

 another. The prices vary according to circumstances, depending upon 

 proximity or the reverse to supplies, freight charges, carriage, &c. The 

 average price for coal and coke may be given as 20s. per ton, and a house 



