1. Tyndall,“Sound,” 3rd edition, Chapter vii. According to statistics compiled for the seaboard of Newfoundland by Mr. R. White, Inspector of Lighth
2. On the Atmosphere as a Vehicle of Sound;Tyndall;Phil. Trans.,1874
3. Scientific Writings of Joseph Henry;Smithsonian Institution,1886
4. Report Upon Fog Signal Experiments;Livermore;Appendix No. v to the Report of the Light-House Board, Washington,1894