Flat blocks are apt to lie closely together in the fire, and obstruct the draft. A fire-place, constructed properly for burning them, should be shallow, not admitting of more than two or three layers being superposed. According to the bulkiness of the peat, the fire-place should be roomy, as regards length and breadth.
Fibrous and easily crumbling peat is usually burned upon a hearth, _i. e._ without a grate, either in stoves or open fire-places. Dense peat burns best upon a grate, the bars of which should be thin and near together, so that the air have access to every part of the fuel. The denser and tougher the peat, and the more its shape corresponds with that usual to coal, the better is it adapted for use in our ordinary coal stoves and furnaces.
Broken peat--the fragments and waste of the cut or moulded blocks, and peat as obtained by plowing and harrowing the surface of drained peat-beds--may be used to advantage in the _stair grate_, fig. 1, which was introduced some years ago in Austria, and is adapted exclusively for burning finely divided fuel. It consists of a series of thin iron bars 3 to 4 inches wide, _a_, _a_, _a_, ... which are arranged above each other like steps, as shown in the figure. They are usually half as long as the grate is wide, and are supported at each end by two side pieces or walls, _l._ Below, the grate is closed by a heavy iron plate. The fuel is placed in the hopper _A_, which is kept filled, and from which it falls down the incline as rapidly as it is consumed. The air enters from the space _G_, and is regulated by doors, not shown in the cut, which open into it. The masonry is supported at _u_, by a hollow iron beam. Below, a lateral opening serves for clearing out the ashes. The effect of the fire depends upon the width of the throat of the hopper at _u_, which regulates the supply of fuel to the grate, and upon the inclination of the latter. The throat is usually from 6 to 8 inches wide, according to the nature of the fuel. The inclination of the grate is 40 to 45° and, in general, should be that which is assumed by the sides of a pile of the fuel to be burned, when it is thrown up into a heap. This grate ensures complete combustion of fuel that would fall through ordinary grates, and that would merely smoulder upon a hearth. The fire admits of easy regulation, the ashes may be removed and the fuel may be supplied without _checking the fire_. Not only broken peat, but coal dust, saw dust, wood turnings and the like may be burned on this grate. The figure represents it as adapted to a steam boiler.