222 GREENHOUSES 



moved slowly from the front to the rear 

 of the fire-box by means of gearing. It is 

 claimed for the self-stoking devices that they 

 not only save labor, but that they are more 

 economical in the use of fuel than is hand 

 stoking. 



Points to Consider. The following points 

 should be kept in mind in selecting a green- 

 house heating boiler: 



1. It should be of ample size at least one 

 size larger than is theoretically necessary. 



2. The fire-box should be deep and spac- 

 ious. This is especially true of boilers for 

 small establishments where a regular fire- 

 man is not employed. 



3. The combustion chamber (the chamber 

 above the grate) should be large enough to 

 insure thorough combustion of the gases. 



4. The boiler should be so arranged that 

 it may be easily cleaned, especially the flues 

 and heating surfaces. 



5. The grates should be heavy but easy 

 to operate and easily removable, so that re- 

 pairs may be made quickly. 



6. The water travel should not be so cir- 

 cuitous as to prevent of rapid circulation. 



7. There should be no packed joints. All 



