280 METHODS OF VENTILATION. 



attached to the front sash by means of a hinge. This curved 

 rod is toothed on the lower side to answer the wheel, and is 

 kept in its place by an iron staple, having an eye through which 

 the sash-handle passes, as seen at a, Fig. 56. A crank and rachet- 



Fig. 56. 



wheel is provided, at one end of the shaft, by turning which the 

 sashes are simultaneously opened and shut, to any distance. 

 This method is simple and efficient. It has been extensively 

 carried out in the unique assemblage of horticultural buildings 

 at Frogmore ; and, as an improvement in the modes of ventilat- 

 ing hot-houses, is considered, by competent judges, the most 

 valuable contrivance that has been introduced during the last 

 half century. By the turning of a small windlass, (which any 

 child may do,) any quantity of air may be admitted, and in- 

 creased or diminished at pleasure, throughout the whole range 

 of buildings. 



The ventilation of forcing-houses, by this compound method 

 of opening the whole sashes at once, is very liable to produce 

 serious results, before the person in charge becomes fully 

 acquainted with the management of it. This, like many other 

 really valuable improvements in gardening, has been adopted, 

 bungled in the construction, mismanaged afterwards, then, 

 lo ! it is condemned, with all the pomp and dignity of practical 

 experience ! The present moment affords an ocular demonstra- 

 tion of this too common fact, Some people suppose, if they 

 can only get mechanical contrivances to accomplish certain ends, 



