Peirce now undertook a range of different scientific studies. He had studied species classification with Louis Agassiz, a Harvard zoologist. He gave the Harvard lectures on The Logic of Science in the spring of 1865 and the Lowell Institute lectures on The Logic of Science; or Induction and Hypothesis in the latter part of 1866. He was elected to the American Academy of Arts and Sciences on 30 January 1867, then from October 1869 to December 1872 he conducted research in astronomy as an assistant at Harvard Observatory. Throughout this time he continued research in geodesy for the U.S. Coast Survey, and he was sent to Europe by the Survey from June 1870 to March on the following year. He continued to progress through the ranks at the U.S. Coast Survey being put in charge of pendulum experiments in November 1872, then promoted to assistant in December of that year. The main task that Peirce carried out in his geodetic work for the U.S. Coast Survey was to measure the force of gravity at various sites both in the United States and abroad. His other task was to use the data from the results of his experiments to determine the shape of the earth. As part of this work he made further trips to Europe, from April 1875 to August 1876, and again for three months from September 1877. Between these two trips he separated from his wife Melusina in October 1876 and this marked the beginning of a problem which would greatly affect his career.