158 HORTICULTURIST'S RULE-BOOK. 



The preceding table gives the standard sizes and principal 

 dimensions of wrought-iron pipe. From this table the amount 

 required for a given amount of radiating surface can be readily 

 computed. This pipe can be purchased of any dealer. 



4. To design heating Surface. 



1st. Find radiating surface by dividing area of glass in square 

 feet by results in Table II. Hot-water pipes can be kept at a 

 temperature of 180 F. if desired. 



2d. Find the amount of pipe by dividing amount of radiat- 

 ing surface by number of feet required per square foot of 

 radiating surface, as given in Table III. Do not use pipe less 

 than 1 inches in diameter for radiating surface. 



3d. Find size of main pipes by Table II., using size next 

 larger when radiating surface comes between numbers given. 

 It is usually better to have several main and return pipes, and 

 divide the radiating surface in sections. 



II. VARIOUS ESTIMATES AND EECIPES. 

 5. Effects of Wind in cooling Glass. (Leuchars.) 



Velocity of Wind Time required to lower Temperature 



per hour. from 120 to 100 Fahr. 



3.26 miles 2 : 58 minutes. 



6.18 " 2:16 



6.54 " .1:91 



8.86 " 1:66 



10.90 " 1:50 



13.36 " 1:25 " 



17.97 " 1:08 " 



20.45 " 1 : 00 " 



24.54 :91 '* 



27.27 " :81 " 



6. Per Cent of Rays of Light reflected from Glass Roofs at Vari- 

 ous Angles of Divergence from the Perpendicular. (Bouguer.) 

 1 2.5 per cent. 



10 . 2.6 " 



