62 MASSACHUSETTS HORTICULTURAL SOCIETY. 



line. Of all the parts of the house, it is most important that the 

 ridge should be of perfectly air-seasoued timber. It should be 

 sawn from a sound log, straight and true to the grain, and free 

 from heart or sap. If you are unable fully to meet these require- 

 ments, in cypress wood, which is often difficult, I would advise 

 the use of yellow pine. In fact, in my own practice, I use yellow 

 pine exclusively for this purpose, as I realize the great difficulty 

 in securing a straight line with cypress, under the peculiar 

 exposures and conditions which surround the ridge of a glass 

 house. The ridge should be two by six inch plank and machined 

 as shown, one side being arranged for the reception of the ventila- 

 tor, and the other for that of the roof glass and bars, as shown. 

 A suitable cap three by one and one-half inches, machined as 

 indicated, is securely fastened to the upper edge of the ridge. 



We will next consider the ventilating sash. For ordinary sized 

 houses they should be three feet deep, and continuous on either 

 or both sides of the ridge. The point at which these sashes should 

 be hinged, whether at the top or the bottom, does not admit of 

 much discussion, as each method affords equal ventilating con- 

 veniences, and the advantage gained by hinging to the ridge and 

 relieving the bars of the weight of the sash is so obvious that this 

 method is recognized as the standard, although there may be 

 isolated cases in which the geographical surroundings are such as 

 to make the hanging of the sash at their lower edge desirable. 

 But these cases are so few that this method needs no further 

 comment in a general discussion. 



The cap described has three objects : first, to protect the ridge^ 

 and help it keep its alignment ; second, to support the sash ; and 

 third, to make the joint between the sash and ridge weather tight. 

 The ridge of a three-quarter span house of the above class 

 i-equires support by means of one and one-half or two inch pipe 

 columns, or three by three inch wood posts, about every eight to 

 ten feet. 



Ikon-Frame Greenhouses. 



We will now pass to the more important style of commercial 

 construction, which comes under the head of Permanent or True 

 Economy, and is generally known as Iron-frame construction, the 

 object in view being to make as much of the structure as possible 

 practicably indestructible, but at the same time bearing in mind 

 the requirements and conditions which are peculiar to greenhouses. 



