In Mr. Clerihew’s modification of the blade each film of air, so to speak, flows into the fan directly, until it impinges on the curvilinear part of the blade, and from that point is thrown at a right angle towards the periphery. The column of air being thus less distorted in its progress, there is not only a greater quantity discharged, but much less power is consumed in effecting that discharge--in the common fan it is evident, from the circumstance of the air flowing to an apex, that a great amount of power is wasted in producing the increased velocity with which a column of air equal in volume to the two ingress openings of the fan must pass so contracted an area before it is discharged; hence it is that the fan, as an air-moving machine, has been considered unequal to the screw. The enclosed space of the coffee-curing house at Rathoongodde has an area in the cross section of 100 superficial feet, it is 70 feet long, and a pair of fans are placed at one end. Repeated experiments have shown that, when the fans make 100 revolutions per minute, a cloud of smoke travels to them from the centre of the enclosed space (a distance of 35 feet) in precisely 15 seconds, hence we have 100 × 35 = 3500 cubic feet of air discharged in a quarter of a minute, or 14,000 cubic feet per minute; a screw of nearly seven feet in diameter would be required to discharge the same amount of air, and the cost of it in England is 84 guineas, whilst the pair of fans made and fitted up at Rathoongodde cost under 9_l._ In the centre of the enclosed space, with a depth of four feet of coffee in the upper floor, the flame of a candle is blown to a right angle when the whole power of the fans is put on that floor; near to the fans it is extinguished, the air moving forward with a uniformly accelerated velocity from the farther end towards the fans, owing to the constant accessions made by the air entering the enclosed space throughout its whole length.