PITS AND FRAMES. 135 
Fig. 91 shows various forms of brackets, spandrils, etc., 
in cast iron. Those at a and B are square brackets, 
to support shelves, etc. ; c is an obtuse-angled bracket to 
be fixed at the foot of rafters, p a spandril for keeping 
rafters in place at the ridge, and © a bracket for sustaining 
wall-copings. 
Travelling Greenhouses.—An entirely new departure 
has been made quite recently in the introduction of what 
are known as ‘‘ travelling greenhouses.” Speaking briefly, 
these consists of a stout and well-constructed glass roof, 
strongly tied together, carried on a number of small iron 
wheels, with flanges, which are fixed just below the 
plates, and run on narrow iron rails resting on stout 
horizontal plates, which again are supported by low brick 
walls, or piers of the same placed at intervals. The sides 
are so constructed, by means of overlapping woodwork, 
as to be almost, if not quite, air-tight, and the lower part 
of the ends, which are usually constructed of wood, are 
made separately, like shutters, and hung from a kind of 
plate so as to lift up when required, and allow of the 
structure passing over any crops of a moderate height 
without injuring the latter. The heating apparatus, where 
any is provided, must of course be portable with 
the house, or else be of a temporary or easily removable 
description. In the former case the pipes are usually 
slung from the roof, near the eaves, and the boilers are 
either portable, or else so situated and fitted as to work 
either to right or left, as required, without removal. 
The object of this method of construction is to enable 
the glass roof to be pushed over at any time, or when 
necessary, on to another crop or plot of land, and from 
