Grates for Fires, are composed of ribs of iron, placed at small distances from each other, so that the air may pass through the fuel, and the accumulation of ashes be, as 'much as possible, pre-vented .

Grates are peculiarly adapted to the use of pit-coal, which requires a greater draught of air to promote its burning freely, than any other kind of fuel.

In the year 1791, a patent was granted toMr.BENJAMIN Charles Collins, of Salisbury, Wilts, for a grate on a new construction, to be used either in or out of a chimney. This invention is said to be calculated to increase the action of the air upon fire, by augmenting and directing the passage of the former through the latter. Thus the fire may be rendered so intense as to present a perfect white heat; and, as the draught of air is very great, the patentee observes, that all, or nearly all of the un-ignted smoke is carried down into the fire and there consumed, instead of passing off in the common way." To effect this purpose, he constructs one or more air-flues provided with stops, by which he may at pleasure promote the draught of air to the requisite degree of heat.

Grates of this construction are asserted to be very useful for lighthouses, and other places requiring a strong fire, such as laboratories, brew - houses, smelting - furnaces, glass-houses, etc. - For a more circumstantial account of this patent, we must refer the reader to the 8th vol. of the Repertory of Arts and Manufactures.