88 MASSACHUSETTS HORTICULTURAL SOCIETY. 



Ventilation. — How the ventilatiou shall be aiTanged in the 

 house depends on the form of the house and the plants to be 

 grown in it. In the old-fasliioned greenhouses the ventilation at 

 the ridge was generally provided for by means of a few detached 

 sashes opening at different points on the roof, either hinged or slid- 

 ing, and usually operated with a cord and pulley or a lever attached 

 to each sash. The great amount of extra labor and inconvenience 

 of this plan was not its only fault. When the sashes were opened 

 for ventilation there was a strong draft, the warm air of the house 

 escaping at one opening and the cold air rushing in at another. 

 This was likely to occur with the most careful handling on the part 

 of the operator. 



The present system of long lines of ventilators opening gradu- 

 ally and together by means of a gear and worm apparatus, or 

 other device, is a change for the better which those who have used 

 both the old and the new Avay can best appreciate. The usual 

 practice is to hang the upper ventilators to the ridge. Sometimes 

 the hinges are placed at the bottom of the sash so as to open them 

 out from the ridge. There does not seem to be much difference in 

 the two plans in regard to ventilation or protection from the winds 

 when in use ; there is, however, a decided difference in the 

 mechanical construction, in favor of having them hung to the 

 ridge. It is usual to place only one line of ventilators on a three- 

 quarter-span house at the ridge, and no matter how they are hung, 

 there must always be more or less trouble with winds on one side 

 of the house or the other. To avoid this difhculty and increase 

 the amount of ventilation, in some modern three-quarter-span rose 

 houses two lines of ventilators have been adopted at the ridge. 

 On windy days the ventilators in the opposite side of the roof can 

 alw^ays be used. While it involves some additional expense for 

 ventilating apparatus, it secures perfect ventilation and freedom 

 from injurious drafts. For rose houses and others which are to 

 be run in the sunnner mouths, side sash ventilators opened in 

 connection with the top ventilators will reduce the temperature in 

 the house on a hot day to within a few degrees of the outside 

 temperature. This double ventilation forms a current under the 

 glass so that most of the heat from the roof passes out of the 

 upper ventilators and does not come in contact with the plants. 

 Where the sides of palm houses and conservatories are of consid- 

 erable height, the side ventilation should be placed close up to the 



