National Geographic : 1941 Jun
Petroleum Serves-From Lamps to Wheels ( iNatlOnai ueograpnic society koularnrome ny is. Antlony jtewart To Whip Jack Frost, Oil Heaters Burn in Citrus Groves on Chilly Nights For years smudge pots were used, but they gave off offensive smoke that hung in clouds over orchards on frosty mornings and besmirched the community far and wide. Now smokeless oil heaters have come into use. When cold threatens, elaborate alarm systems warn fruit growers to light up. Redlands, California.