GREENHOUSES. 



397 



by ventilators in the back wall, which 

 are made to swing on pivots, and open by 

 means of long iron rods having holes to 

 fix on pins driven in the wall, so as to 

 regulate the proportion of air at pleasure. 

 To prevent these ventilators from being 

 unsightly, a square piece of trellis-work 

 is placed over the opening inside the 

 house." 



This is altogether a very splendid green- 

 house — such, indeed, as few can boast of. 

 We would, however, have preferred hav- 



ing the walks of pavement, instead of the 

 bars of wood, and the back wall removed 

 and substituted by glass ; and as such a 

 house is more fit for well-grown specimens 

 than for a general collection, we would have 

 dispensed with the stage altogether, and 

 placed the plants on the floor in groups 

 or singly, as circumstances might direct. 



Fig. 547 is a section of the greenhouse 

 at Poltalloch, forming part of the series 

 of span-roofed houses recently erected 

 there, a a is a raised platform covered 



Fig. 547. 



with polished Bangor slates, for the larger 

 specimen of plants, supported by polished 

 Caithness pavement in 6-feet lengths, and 

 3 inches thick, set on edge, and forming 

 one side of the passages, which pass all 

 round ; b b polished slate tables, for 

 smaller plants, supported on ornamental 

 cast-iron brackets let into the pavement 

 in the passage, and into the side walls. 

 This slate tabling is 6 inches clear of the 

 side walls, to permit the heat from the 

 hot-water pipes e e to rise freely ; c is the 

 half gutter already noticed, employed 

 where the height of one house is much 

 lower than that adjoining it ; d d the 

 tubular cast-iron columns which support 

 the bottom parts of the roofs, and also 



take down the water from the valleys or 

 gutters above them ; / ornamental cast- 

 iron parapet, 6 inches high, planted on 

 the edge of the cast-iron gutter, but hav- 

 ing spaces under it 1 inch in the clear, to 

 allow the melted snow to pass freely into 

 the gutter below it, while it prevents the 

 slipping down of a body of snow upon the 

 glass roof of the lower house next to it ; 

 gg the ventilating tubes under the floors of 

 the passages ; h h h h the same in the 

 centre of the partition walls ; i i i i the 

 3-inch tubes connected with the last, 

 discharging fresh air at their orifices, on 

 each side of the partitions, between the 

 compartments. Ventilators are placed 

 in the front wall, as seen in the general 



