CONSTRUCTION AND HEATING OF GLASS HOUSES. 73 



liberal syringing, and if the necessary moist condition of the 

 atmosphere is maintained, the effect of hot water and steam heat 

 upon the plants will be equal ; therefore, we find the merits of 

 these systems as follows : 



In favor of the steam system: Low first cost, being from sevent}'- 

 five to eighty per cent of that of a similar hot-water plant. 



In favor of the hot-water system : Economy of fuel and ease of 

 management ; absence of the necessity for repairs ; positive circu- 

 lation, and consequent radiation of warmth under all conditions of 

 the fires. 



The objections to each of these systems are ; To the steam 

 system-: Additional fuel consumption, necessity of skilled and 

 continual attention; liability to accidents, leaks, etc, and conse- 

 quent cost of repairs ; total loss of radiation when fires become 

 so low as to allow the temperature of the water to drop below 

 212°, and consequent loss and damage to stock. 



The hot-water system has one disadvantage only, namely, higher 

 first cost. I am thus compelled to give the preference to the 

 hot-water system, and will proceed to mention some details which 

 are desirable in its arrangement. Of course, it is understood that 

 the heating of greenhouses must be by a direct system, as no 

 indirect system would give a sufficiently even distribution of 

 the warmth for this purpose. 



Two systems of water heating are in use ; the first being known 

 as " upward circulation," by which we understand a continual 

 upward grade of the pipes, to a point farthest from the boiler, and 

 a downward grade from that point back to the boiler. The 

 second is known as "drop circulation," where the rise to the 

 highest point is taken directl}' over the boiler, the pipes then 

 grading downward all the waj' back. I do not think either of 

 these systems should be given a preference as regards their effect, 

 under ordinary' circumstances; but as the "upward" system 

 presents so many less difficulties in the course of construction 

 than tlie " downward," I would strongl}- advise its being used in 

 all cases, unless some peculiar conditions of grades or other 

 details of arrangement of the houses exist, which might render 

 the "downward" system advisable. 



Benches. In the furnishing of a greenhouse, we must not 

 overlook the benches. If lew-cost benches are desired, the}' may 

 be made of cypress, but for the commercial grower who is 

 interested in future profits and small repair bills, I would advise 



