Starting in 1912, he taught analytical mechanics for over 20 years. German physicist Wilhelm Röntgen discovered x-rays in 1895, and his first research paper was published at the end of December. An Austrian newspaper reported the results a week later. After reading those reports, LeConte found cathode ray tubes that his late uncle John LeConte had obtained for the university's physics lab. LeConte and his associates were able to construct an x-ray machine and produce images of a bullet lodged in the arm of a young boy within a week of the newspaper reports of Röntgen's discovery. LeConte also studied the materials problems of gas turbines, and built a harmonic analyzer to study the performance of electric power transmission lines. He was a professor at U.C. Berkeley for his entire career that lasted 45 years.