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Where ventilators open from the header there is greater danger from 

 the rain getting in even if the ventilator is partially closed. Where the 

 ventilator opens from the ridge the air can come in with very little danger of 

 any rain getting in. An important point to be considered in ridge ventilation, 

 whether ridge or header type, is that both lines should work separate in order that 

 in the case of a strong wind from one side the ventilators on that side may be 

 closed, while the others will remain open and complete ventilation of the house still 

 be carried on. Some growers complain that the ridge type of ventilators allow an 

 inward rush of air which has caused severe checks on the plants, while in the header 

 type this rush is broken and the air admitted is distributed evenly through the 

 house. 



■Gable end ventilation as yet is the idea of some one grower. This shows the arrange- 

 ment of the ventilators which open out. Houses also have ridge and side ventilators. 



Gable end ventilation is probably more or less of an experiment as yet, but it is 

 being advocated by some plant owners. They would advise a continuous or broken 

 line of ventilators on a wide, high house set in a horizontal position or two or three 

 jsmall vents in a perpendicular position. In both cases these vents should be above 

 the door. It is quite possible that very little more ventilation will be needed in 

 many houses than that given by the door, which should be built sufficiently large 

 ■enough to be used for admitting a waggon. All forms of ventilators are usually 

 ■operated by a system of ventilating machinery which is controlled by a wheel or a 

 chain driving some form of gear which by revolving will open the ventilators. 

 Many forms are on the market, and it is difficult to choose as each and every device 

 lias its exponents. In large houses a system running 150 to 200 feet should be 

 secured in order to opon the maximum amount of glass with minimum labor. For 

 the smaller houses, grovvers in many cases do not btiy ventilator machinery, but have 

 some appliance such as an iron rod with holes drilled in it, which, when the vent is 

 opened fit on to nails set on the plate. These may be all right in some cases, but as 

 a general rule, in any house 20 by 60 ventilating apparatus will pay for itself in the 

 amount of labor saved. AVhere two systems are necessary to open up the glass they 

 should be located so that both can be operated from the one point, preferably the 

 ■centre of the house, instead of being located at both ends of the house thus neces- 

 sitating extra labor. 



