64 MASSACHUSETTS HORTICULTURAL SOCIETY. 



inch is ample ; where supports are from seven to eleven feet apart, 

 two and one-half-inch by one-half-inch iron will serve, and so on. 



The rafters are tied at their upper ends by iron brackets which 

 have a recess or socket to receive the wooden ridge already 

 described. I have often been asked why I do not use an iron 

 ridge, and I suppose this question has come to the minds of many 

 present, when considering this subject. An iron ridge is unneces- 

 sary, and presents many objectionable features. A wooden ridge 

 and cap of some description are necessary for the weather-tight 

 and proper connecting of the ventilators and roof, and to add an 

 iron ridge, of such dimensions as would give to the building the 

 stiffness and stability that a two by six-inch yellow pine ridge will, 

 would so add to the amount of shadow thrown upon the house as 

 to be prohibitive ; it would also entail additional and unnecessary 

 cost. The bracket should also have conveniences for carrying the 

 shaft of the ventilating apparatus. We have then in this bracket 

 a combination of three parts. First, a convenient and practicable 

 tie for the rafters ; second, a suitable means for connection between 

 the ridge and the iron frame ; and, third, bearings for the vent 

 shaft, combined in one casting, which not only causes a saving of 

 first cost, but a saving of labor in the course of erection. 



These pieces comprise the main supporting trusses of the 

 structure, and we will now consider the parts which are requisite 

 for the tying of these trusses or sections together, and for the 

 support of wood and glass on those parts between trusses, which 

 as I have before stated are placed eight feet, four and one-eighth 

 inches apart. This is for glass sixteen inches wide. If narrower 

 glass is used, a lesser spacing of the trusses will be necessary. 



The posts are tied together by means of two lines of angle iron 

 purlins, the lower of which is placed about one foot, six inches 

 above the ground, and is of three by two inches by three-eighths 

 inch angle. Its uses are, first, to tie the posts together, and, 

 second, to give suppox't to the two-inch by one and one-fourth 

 inch by one-fourth-inch angle eaves, or gutter purlin and plate 

 above, by means of a light intermediate post connecting the two 

 together. These two purlins so connected give ample support to 

 that portion of the roof below the lower roof purlin ; also to the 

 gutter and header supporting the side ventilating sashes. The 

 lower purlin is also used as a back support for the side bench, and 

 thus obviates the necessity for any back legs, or for attaching this 



