When you cross the Mexican border at Laredo, oil enters your consciousness--and your clothes. It is everywhere, the thick, odorous _chapapote_ which furnishes the fuel for Mexico’s locomotives, the energy for every Mexican industry which has no water power, the pavements for her streets, and, I am still convinced, the heavy lubricant with which the sandal-clad brakeman of our train eased an incidental hot-box. In Tampico, whence comes all the oil of Mexico, the heavy, black “crude” is even more ubiquitous. It “tars” your shoes when you walk abroad; it decorates your clothes when you ride in anybody’s motor car or motor boat; it oozes between your toes and sticks in your hair when you bathe at the beach. But the physical presence of oil is as a whiff from the dead well at Dos Bocas compared to its spiritual domination in all Mexican affairs. Oil is the greatest--I had almost said the only--wealth of Mexico to-day, its possession the issue of one of the mighty diplomatic battles of recent times, while the taxes and graft of it have fed the wellsprings of ten years of devastating revolutions. Far and away and by many fold, oil is the largest single item of export of Mexico, and the varied needs of the oil industry and of the beneficiaries of that industry dominate the imports as well. To Tampico go shiploads of steel, machinery and supplies, and trainloads of soap and shoes; the factors which build civilization go chiefly and all but alone, in Mexico, to the oil fields. Oil dominates the political life of the country not because oil companies or oil millionaires seek to control the Mexican government but because the vast unbelievable wealth which is pouring into the coffers of that government in taxes and in tribute makes revolution a game the stakes of which eclipse any sum or any potentiality of wealth or power which has ever been known in Mexico. Oil is the inspiration for the “nationalization” policies which, forged by foreign radicals and given edge by Mexican cupidity, the Carrancistas wrote into their Constitution of 1917. This policy of nationalization, the decrees, the laws, the taxation and the graft which have come in its train, have brought into the field of diplomatic controversy the whole problem of the right of a government to enforce radical, socialistic or, if you will, bolshevik policies against foreign interests which may have entered a country and developed it under older, more conservative ideals and systems of government.