14 OENAMENTAL FOLUGE PLANTS. 



GLAZING AJSTD VENTILATING. 



jlB shall pass only a few remarks on this subject, to 

 enable the amateur to make a proper selection 

 of material. For general use we have found the 

 21-oz. sheet glass the most serviceable, as it is sufficiently 

 stout to resist all ordinary pressure. It is also wise to use 

 a medium-sized square ; neither very small ones nor over 

 large ones are to be recommended. A very convenient 

 size for the panes used for the roof is about two feet six 

 inches in length, and nine inches in breadth ; the same 

 width should also be used for the front sashes. 



On the subject of Ventilation we must speak more de- 

 cidedly, for it is of the highest importance. A constant 

 renewal of air in plant houses is essential to the well-beiag 

 of its occupants ; indeed, where the necessary temperature 

 can be maintained, -we would never quite close the house, 

 day or night, except in severe weather. We wish, however, 

 to be properly understood upon this subject. By good ven- 

 tilation, we mean always to avoid draughts and currents of 

 cold air, these being most injurious to plants of all kinds. 

 The adoption of the underground ventilators recommended 

 in the construction of the plant houses will entirely ob- 

 viate any ground of apprehension on this point ; and if the 

 sides of the ventilators in the lantern roof are covered with 

 fine gauze wire or perforated zinc, evil will be most satis- 

 factorily guarded against. The use of this latter precau- 

 tion will only be necessary during winter, as in the summer 

 a greater volume of air may be admitted with advantage, 

 and consequently the heated portion will require a readier 

 means of exit. Plant houses ventilated upon these princi- 



