HEATING THK ORCHARD. 287 



than oil at $5 to $6 per hundred gallons. However, the additional amount 

 of labor required and the less heat produced by coal, makes oil in the 

 end the most economical fuel. 



The best grade of oil is what is known as fuel or smudge oil distillate. 

 Such oil should test a specific gravity of twenty-eight to thirty-two. Many 

 growers make the mistake of getting a cheap residue, with a specific 

 gravity of from fifteen to twenty. This oil will not burn clean and con- 

 tains so little volatile matter that the heat produced is not 25 per cent of 

 what it should be. Heavy oil, such as this, ought not be used for orchard 

 heating. 



The best method of handling oil through the orchard is to haul same 

 either in barrels on a small wagon, or in large wagon tanks, driven up 

 and down the rows, filling directly into the heaters, either by means of 

 hose attached to the tank or by buckets or pails which can be filled from 

 a spigot in the back of the tank wagon. This is the quickest and most 

 effectual method for handling oil, both for original and additional filling 

 when required at night. 



RELATION OF SMOKE TO THE PREVENTION OF FROST. 



Smoke will ward off a light frost in the same manner as will heavy 

 clouds. For increase in temperature, however, or for holding the heat 

 in the orchard, after it is produced by heaters, it is absolutely useless 

 and the grower who expects to save his crop by the means of a blanket 

 of smoke will invariably lose out. Experiments have been made with 

 smoke so dense that men could not stand it, and it was found that the 

 smoke did not have a particle of effect on the thermometers. Then, too, 

 those who depend upon smoke for the protection of their crop, will very 

 likely discover that the blanket of smoke, instead of being over their 

 own orchard, is over their alfalfa field or their neighbor's orchard, driven 

 there by a light wind that invariably exists during frost fighting. 



The great advantage and in fact the only advantage of smoke is in 

 warding off the direct rays of the sun early in the morning. This is a 

 great advantage, and all orchard heaters should give off a sufficient 

 amount of smoke to accomplish this purpose. Smoke is for the most part 

 unburned carbon and any system of heating that produces more than the 

 ordinary amount of smoke is therefore very wasteful. The ideal way 

 would be to have a heating device that was absolutely smokeless and 

 then, by burning a few barrels of tar in the orchard to produce the 

 desired smoke just before sunrise. Up to the present time no device has 

 ever been invented that was smokeless, regardless of claims made by the 

 manufacturers. 



Some heaters, however, owing to oxygen-consuming arrangement with 

 the fuel, are more nearly smokeless than others, and these devices have 

 been found more economical. As an example, the common lard-pail 

 heater, which is patented by no one, will save fruit crops just as sue- 



