Mechanical ventilation, c 1894.

'Mechanical Ventilation on the Lateral and Downward Principle, by Impulsion, or the Plenum System, applied to a School.' Plate taken from 'The Boyle System of Ventilation' by Robert Boyle, published in 1894. The plate highlights how downward mechanical ventilation spreads diseased air, as described in a Local Government Board report. The book compares this system of ventilation unfavourably with a 'Natural System of Ventilation' illustrated elsewhere.