23 



to multiply this by the length of the house in feet and the result will be the cubic 

 contents. For example, supposing the house in question is 100 feet long, it contains 

 150£ squares or square feet, and 150 J multiplied by 100 equals 15,050 cubic feet. The 

 whole operation requires less time than it takes to describe it and will apply, of 

 course, to a house of any shape or size. It may be added that if the cross-section 



Fig. 5.— Diagram illustrating method of determining cubic contents of greenhouses (after Galloway). 



paper can not be obtained readily the sections or squares can be laid off with a rule 

 and lead pencil and practically the same results obtained. In any event, it is only 

 necessary to get an accurate outline drawing of the section of the house, and by pro- 

 jecting this over squares as indicated the number of square feet ia the section can be 

 readily determined. 



SELECTING A TIME TO FUMIGATE. 



Care should be taken to select a night when the houses can be ventilated the 

 required time without injury to the plants and when there is little or no wind. 



PREPARATION OF THE HOUSE FOR FUMIGATION. 



On account of the very poisonous nature of the gas, it is necessary to arrange a 

 number of ventilators, the more the better, so that they can be easily opened from 

 the outside. It would be very dangerous to enter the house while it contains the gas. 

 All broken glass should be replaced and holes stopped up; a thoroughly wet piece 

 of newspaper will close a crack effectually or take the place of a broken glass if nec- 

 essary. It is best not to permit the gas to get into fire pits or engine rooms; these 

 should be cut off from the space to be fumigated. 



In case of a large range of houses opening into each other it is best to separate 

 them into several sections, by tacking up building paper or oiled cloth, so that each 

 section may be fumigated separately and at different times. The work may thus 

 be done with greater ease and care, and with less danger to the plants. When all 

 the larger cracks and openings have been stopped up, if the house is quite old or 

 loose it is well to wet the roof on the outside just before fumigating. The water will 

 fill the cracks between the glass and will assist in making the roof tight. 



METHOD OF MAKING THE GAS. 



The materials required are 98 per cent cyanide of potash, best secured in 5 or 10 

 pound cans at 35 to 40 cents a pound, and commercial sulphuric acid at 3 to 4 cents 

 a pound. 



