A method of boring a hole in the earth such as for passing under obstacles, not limited, but including roadways, rivers, dikes, canals or other inexcessible areas where it is impossible to trench a ditch including the steps of advancing a rotating drill string in a direction inclined to the earth's surface...http://www.google.ca/patents/US4953638?utm_source=gb-gplus-sharePatent US4953638 - Method of and apparatus for drilling a horizontal controlled borehole in the earth
