2052. The mode of heating now called Polmaise appears to be as old as the time of Bradley (1719), as he speaks of a mode of circulating warm air in a plant-house, invented by Dr. Desaguliers, by means of chimneys erected in rooms adjoining the house. This plan, however, appears to have lain dormant, or to have been only occasionally practised, till it was used by Mr. Sylvester at Derby to heat the Derby Infirmary, and the hothouses, &c., at Belper. It was afterwards tried at various places with indifferent success; till at last it was used at Polmaise, near Stirling; and, having been frequently noticed in the Gardeners' Chronicle, it has become well known and used extensively.