454 



house. The effect is astonishing and would surprise plant growers in 

 gênerai. 



Caution is needful not to give so much water as is done in single 

 roofed houses. 



4^^. Almost total cessation of insects. Former ly thèse pests 

 abounded with me ; now they rarely appear, and when they do, they 

 are few in number and are easily got rid of. From this fact it may be 

 inferred that when plants are grown in a condition of atmosphère 

 favourable to perfect health, they are but little liable to attacks by 

 insects which often spoil their beauty. 



A remarkable instance of the value of double roofs to stove and 

 Orchid houses occurred in January 1864. We had 4 days and nights 

 of hard frosts, the thermometer not rising to 32** by day and falling 

 to 18° at night. Just as the frost began an accident happened to the 

 heating apparatus and ail the water ran ont of the pipes and the acci- 

 dent could not be repaired until after the 3rd night of frost. The 

 température was 56'' in the morning when the lire was discontinued; 

 24 hours after this, the réduction of heat was only 3". The following 

 morning or after 48 hours, only 3° more, and in the 3rd night 2 "more 

 were lost : thus making a réduction of only 8°, viz. from 56° to 48 , in 

 72 hours. Nothing was injured, which is a striking proofof the value 

 of double glazing in winter, for without it, every plant would hâve 

 been frozen and the loss would hâve been immense. With double 

 glazing, gardeners and employers may in severe weather sleep in peace. 



Another year's expérience has fully confirmed ail the advantages 

 before narrated. 



A market-gardener at Colney Hatch in England has for some 

 3 years tried the system, for gi'owing early cucumbers for Covent 

 Garden-market, with great saving of fiiel. 



In Eussia the System has long been used for planthouses. 



I will conclude byenquiriugwhether in other continental countries 

 the System has had a fair trial and with what resiilts.»^ 



