2079. Fixed roofs are either formed of a series of bars of iron or wood, proceeding at once from the front parapet to the back wall, or from the base to the centre; or they may be composed of sashes, placed beside each other, or between rafters, as in common lean-to houses. Roofs of this fixed kind have been approved of by Knight for vines; by Beattie of Scone, for peaches; and by some, cultivators for the culture of pines and palms; but, except for the latter purpose, the general experience of gardeners is (in our opinion, very justly) against them. It is to be observed, that in all cases of fixed roofs, shutters for ventilation are formed in the parapet, and in the upper part of the back wall immediately under the roof. Economy in first cost, and less breakage of glass afterwards, are the chief arguments in their favour: the latter advantage, however, is generally denied, it being improper glazing rather than the moving of the sashes, which occasions the breakage of glass.