Forcing Frame – Vaporarium
“The Vaporarium or Forcing Frame stands by the west side of the orangery. It is built of wood and equipped with slanting windows, and filled with horse-dung which is covered with tanner’s bark. Numerous pots may be seen here, filled with the finest sifted humus in which the seeds of tropical plants are sown. In the summer, thanks to the sun’s and the earth’s combined heat (as warm as in the horse’s belly), these seeds are brought to germination. The height of this hotbed reaches 3 1/2 ells.”
Carl Linnaeus, Hortus Upsaliensis 1745
This is where Linnaeus’ Vaporarium stood, a forcing frame two metres high used to force plants from seed. It was warmed partly by the sun’s rays and partly from below, when horse-dung and tanner’s bark “burned” together. It is not known exactly what the forcing frame looked like.