BOTTOM HEAT ITS BENEFITS AND METHODS. 29 



season and the nature of the plants for which the bed is intended. 

 The loam taken from the first six feet in length of the bed is to be 

 carted to the other end to be used in covering the manure on the 

 last six feet. Plot manure from the heap should now be carted into 

 the pit and carefully spread and tramped down ; the depth required 

 will vary from six or" eight inches in spring to ten or twelve inches 

 in winter. The loam from the next six feet in the length of the 

 bed should be immediatel}' thrown on to the hot manure, and sashes 

 placed over it, and the excavation thus made filled with manure 

 as before, and the process repeated until the bed is completed. 

 The depth of loam thrown over the manure will vary with the work 

 required, hardy plants, such as lettuce and radishes, requiring 

 eight or ten inches for thrift}' growth ; while the depth needed for 

 tomatoes, cucumbers, and other tender plants will be only six inches ; 

 the less the depth of loam used the more the heat of the manure 

 is felt by the plants, and the more care will be required to water 

 sufflcientl}^ often. 



Where a considerable depth of manure is used with a light cov- 

 ering of loam, in preparing for tropical plants, the heat for the 

 first few days is apt to be excessive, and care will be needed in 

 airing the bed both day and night, to prevent destruction of the 

 plants ; the excess of heat generally passes off after the first week. 



A well made hot-bed will retain considerable heat for six or eight 

 weeks from the time it is started. The heat gradually subsides 

 from the time of beginning, and this is not objectionable in the 

 spring, when the weather is constantly growing warmer, and the 

 bottom heat is less and less needed. 



In the severe weather of winter, however, the hot-bed is rather 

 difficult to manage, and unless fully twelve inches of manure is 

 used the heat will sometimes become exhausted before warm weather 

 comes and cause trouble. In fact a great deal of skill and care 

 is required to run hot-beds sucessfully in winter. 



When a constant temperature of 60° to 70° degrees of bottom 

 heat is required in a greenhouse for a considerable time, the use of 

 fire heat will be found much more convenient and satisfactory. 



The smoke flue is the simplest form of heating apparatus, but is 

 open to objection from the high temperature of the parts near the 

 fire as compared with the more remote parts, and where large 

 greenhouses are required, the heating is done much more satisfac- 

 toril}' by hot water pipes. Another objection to the flue is the risk 

 of fire from the hot brickwork near the furnace. 



