No. 4.] GREENHOUSES. 393 



Arrdngemeiit of the Fipes. — To obtain the best results, 

 the pipes should be placed at nearly equal intervals through 

 the house (Figs. 2, 3 and 4), and not in large coils or 

 stacks. Most of them should be above the benches, especially 

 for those plants Avhose roots are liable to injury by too 

 much heat and moisture, like the carnation, etc. Plants 

 much subject to leaf diseases should have some of the pipes 

 under the benches, as should also cutting benches and seed 

 beds where the root growth is to be encouraged. Two 

 methods of arrangement are most in use: Fig. 15, where 

 the heated water rises to the highest point at once, and falls 

 continuously to the boiler ; and Fig. 16, where the pipes 

 continue to rise from the boiler to the farthest end of the 

 house, and then fall by a regular grade to the boiler. Both 

 of these give good results, but in neither case should the 

 pipes go below the grade and rise again to above the last 

 level. The amount of pipe required will depend upon lo- 

 cation, construction and the kind of crop to be grown, the 

 quantity varying from one foot of heating surface of pipe 

 to three feet of glass surface, to one foot to ten feet of glass 

 surface. 



In all cases the diameter of the flow pipes and the radiat- 

 ing surface of pipes should be larger than would be required 

 to keep up the desired heat when the heating plant is run 

 at its fullest capacity, for it is not economy to force the 

 boiler to its utmost. Two boilers are often put in, so that 

 one only may be run during the fall and spring, and both 

 together during the winter when needed, and that in case 

 of the breakdown of one tlie other one can do the work 

 while repairing is being done. 



V Ventilating Fixtures. 



Of the many ventilator " lifters" in use, those that apply 

 the force by means of a light shaft directly against the lifting- 

 end of the sash are perhaps the best. Some of this type are 

 very expensive, while many are low in price. The lifters 

 that work with the shaft and elbow joint are largely in use, 

 but greater force is required with them than with the first- 

 mentioned types. 



