The Theories and Practice of Centrifugal Ventilating Machines #250607

Little if anything was done towards the application of machinery to the purposes of ventilation until very recent years, although, so early as the year 1657, Agricola, in his interesting work De re Metallica, gives particulars and a drawing of a mechanical ventilator for mines, driven by water-power, and at the Hartz mines, nearly 200 years ago, another, somewhat similar to the Struve, was in operation.