272 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 



a few groves baskets and stoves burning coal were used, but in general 

 these did not give as satisfactory results as the oil heaters (fig. 7). 

 Oiled shavings burned in the grove gave little help, and is a method 

 that cannot be depended upon. 



The oil pots used varied in capacity from one to four gallons. 

 Some of them were open pots, the shape of flower-pots, some were 

 rectangular with sliding tops, and others were either oblong or round 

 and provided with stacks (fig. 8). The pots which had stacks had 

 the tops covered, but had drafts which could be opened to let in the air. 

 The oil used was a low grade crude oil with asphaltum base, and cost, 

 when put down in the grove, about 3 cents a gallon. 



The lighting was commonly done by means of torches that held a 

 gallon of fuel, and had a long spout, inclosing an asbestos wick. 

 Engine distillate, gasoline, or kerosene was used as fuel, and when the 

 torch was tipped some of the burning liquid fell into the pot (fig. 7). 



In some cases where new heaters were being used considerable delay 

 was occasioned by the difficulty in lighting the pots, several visits 

 with the torch being necessary. After pots had been burned for 

 some time and had become thoroughly sooted the lighting was accom- 

 plished fairly easily. In order to avoid such interruption at a critical 

 period, it seems desirable, either to place a bundle of excelsior in the 

 chimney of each heater, or to light and burn each heater for a half- 

 hour or more before they are required to be lighted during a freeze 

 (fig. 9). 



The pots were filled from tank-wagons. Sometimes the oil was 

 drawn from the tank-wagon into buckets and poured into the pots 

 and sometimes a hose was attached to the tank and the oil run directly 

 into the pots. The tank-wagons were filled from storage tanks which 

 were made of steel or of concrete. 



These varied in capacity according to the acreage and estimated 

 needs, and many growers found that their estimates had been too low. 

 When twenty or twenty-five cold nights may be expected it is well to 

 have a storage capacity of about 1000 to 1500 gallons per acre in 

 addition to full pots. 



As a result of the difficulties experienced in this freeze the tendency 

 hereafter will be to use larger pots of seven to ten gallons capacity and 

 thus avoid the necessity of refilling in the night. The night filling 

 is expensive, because of the higher wage paid the men and the smaller 

 amount of work which they do in the night than in the day, and is 

 responsible for much of the spilling of oil which occurs during the 

 filling of the pots. The oil kills the roots with which it comes in 

 contact, besides rendering the soil unfit for use. Some growers spent 



