contains observations, but contradictory observations; while, as regards the establishment of any principle which should reconcile the conflicting results, it leaves our condition unimproved."
A distinction is here drawn, and again recognized in his letter, that goes to the root of the subject; the distinction, namely, between experiments on fog-signals made for direct purposes of utility, and similar experiments conducted with a view to the establishment of scientific principles. This discrimination is all-important. It is no doubt possible to have both objects more or less in view in such an inquiry; but it is also possible that either may so predominate as to characterize the respective courses of investigation, and yield very dissimilar results. Elaborate experiments may promote practical ends, and contribute little or nothing to science; or they may advance scientific knowledge without any immediate influence upon practice. It was claimed by Prof. Henry, in his Appendix to the report of the Lighthouse Board for 1874, that the researches of the board had been more extensive on this subject than those in England, as well as prior to them; but the question remains, To what purpose were they carried on? The answer to this question, defining the character and object of the inquiries, is immediately given in the statement that the American results of "practical importance" are in advance of the English. The writer in the Nation speaks of "American science" as bearing Baconian fruit, such as Daboll's trumpet and Brown's steam-siren. These devices and construction are, no doubt, highly important, but there is certainly a wide difference between the invention of whistles and systematic inquiries into the causes of acoustical phenomena. No one doubts the immense value to the country and to civilization of the labors directed by Prof. Henry, as chairman of the Lighthouse Board; but he has himself declared their practical character, and how broadly true is this characterization appears from a passage in a letter which he wrote to the Secretary of the Treasury, dated February 22, 1875, defending the Washington board against an attack made upon it in Congress. It is noteworthy, also, as showing that, when Prof. Henry wishes to protect himself from adverse criticism, he falls back upon the verdict pronounced by Prof. Tyndall in this very matter of fog-signals. Prof. Henry said: "The board has a standing committee on experiments which has accepted and sought to test every invention that could be supposed to aid the mariner. Many illuminants, various devices in engineering, expedients for floating aids, plans, and theories of all kinds, have received its attention. To this accusation can be opposed on behalf of the board the verdict of foreign nations, the tributes of scientific associations, and the contented judgment of maritime and commercial men from whom no complaints are received. Its buoys are excellent in their construction; its buoy-service is well performed; its light-ships are equal to any in the world; its lights are entirely satisfactory to the commercial and nautical men for whose interest they are maintained; and its fog-signals surpass, in the finding of Prof. Tyndall, who conducted a series of experiments for the Trinity House Board, those of all other nations, and have been adopted for England." But it is claimed that Prof. Henry's investigations constitute also an important contribution to "American science," in relation to fog-signaling. Prof. Tyndall denies that they have at all advanced our scientific knowledge upon the subject, and the writer in the Nation had this denial before him when he wrote. It was his plain business, then, to disprove it if he could, and give the evidence that Prof. Tyndall was in error.
The simple question is, What new scientific principles have been established, or what causes elucidated by
