manufacturers upon the [tax] free list." Starting in 1901, the discovery of new oil fields in Texas causes the price of gasoline to drop to between 18 and 22 cents per US gallon by 1906, undercutting farm ethanol markets In 1908, the Ford Model T is introduced. Early models had adjustable carburetors to run on ethanol with gasoline as an option. In 1909, the U.S. Geological Survey reports: "In regard to general cleanliness, such as absence of smoke and disagreeable odors, alcohol has many advantages over gasoline or kerosene as a fuel… The exhaust from an alcohol engine is never clouded with a black or grayish smoke." Overall, alcohol was "a more ideal fuel than gasoline." In 1914, the Free Alcohol bill is amended again to decrease the regulatory burden and encourage alcohol fuel production in the U.S. In 1917 Alexander Graham Bell says: "Alcohol makes a beautiful, clean and efficient fuel… Alcohol can be manufactured from corn stalks, and in fact from almost any vegetable matter capable of fermentation… We need never fear the exhaustion of our present fuel supplies so long as we can produce an annual crop of alcohol to any extent desired." In 1918, Scientific American says it is "now definitely established that alcohol can be blended with gasoline to produce a suitable fuel …" Another article notes that the Pasteur Institute of France found it could obtain of ethanol per ton of seaweed. In 1919, Prohibition of beverage alcohol in the U.S. leads to suggestions for more ethanol use as an anti-knock blend with gasoline. Farm belt politicians are split on ethanol as a fuel. While distillers could have a new market for their alcohol, some thought that allowing any distillery to stay open would be a "bargain with the devil." In the 1920s and 1930s, Koolmotor, Benzalcool, Moltaco, Lattybentyl, Natelite, Alcool and Agrol are some of the gasoline-ethanol blends of fuels once found in Britain, Italy, Hungary, Sweden, South Africa, Brazil and the USA (respectively). In 1920, David White, chief geologist of US Geological Survey, estimates total oil remaining in the US at . "In making this estimate, which included both proved reserves and resources still remaining to be discovered, White conceded that it might well be in error by as much as 25 percent." In 1921, leaded gasoline is developed at the General Motors research laboratories in Dayton, Ohio. GM researcher Thomas Midgley,