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XXIX. Observations on the Form of Hot-houses. By the 

 Rev. Thomas Wilkinson. 



Read May 2, 1809. 



Although it is probable, that more depends on ma- 

 nagement, than on the inclination of the roof, in any 

 Forcing-house whatever, yet as it is satisfactory to proceed 

 on something like principles, I endeavoured to ascertain 

 why an angle of 34° was preferable to any other ; which has 

 led me to take a general view of the subject. By pointing 

 out the times, when the sun's rays will be perpendicular to 

 any construction, and the reflexion at the different angles of 

 incidence, we shall be enabled to compare, with some accu- 

 racy, the effects of the sun on different degrees of inclination, 

 abstractedly of internal arrangement, stoves, flues, and cul- 

 ture. Now the angle contained between the back wall of 

 the Forcing-house, and the inclined plane of the glass roof, 

 always equals the sun's altitude, when -his rays fall perpen- 

 dicularly on that plane, provided that the inclination of the 

 plane to the horizon, be at an angle not less than 28° 2', 

 nor greater than 75°. The former is the case with most 

 Cucumber-frames, the latter with many Pineries. It <?iso 



