Frost Injuries and Protection, Secondary Bloom 347 



flames. The oil burner should also show very little varia- 

 tion in the rate of burning when full and when almost 

 empty, and it should be so constructed that the gases are 

 well mixed with air in the process of burning. This in- 

 sures better combustion of the fuel, gives more heat, less 

 smoke, and less soot. 



'A coal burner should have good draft and an open 

 grate so that the ashes will fall out readily. If the grate 

 is too close and the heater is not supplied with side draft, 

 it will soon clog and refuse to burn. The coal burner 

 must also have capacity. At best it seems that it has 

 not been possible to construct a coal burner that will 

 burn satisfactorily for over four hours without refilling, 

 and the heater that will hold twenty-five pounds of coal 

 and is so constructed that the fuel takes fire gradually, 

 has a great advantage over the heater of small capacity in 

 which all the fuel catches and burns at once. 



It should be remembered that large fires are liable to 

 create upward currents that will carry the warm air far 

 above the tree-tops and allow the colder air to settle. It 

 has been suggested that probably more benefit is derived 

 from the slight currents of air produced by the burning of 

 the small fires than from the heat that is actually given 

 off in the combustion of the fuel. Fruit-growers have 

 often given their experience in trying to protect a few 

 favorite trees with large bonfires. One instance comes to 

 mind in which the grower built large fires about some 

 favorite cherry trees. The fires were placed as near as 

 possible without danger of scorching the trees, yet the 

 heat was carried up too high, and the cold air settled and 

 froze the crop. 



