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Rh of fog-signaling as practised in the United States. On the contrary, he acknowledges that in the choice of fog-signals for British use his "strongest recommendation applies to an instrument for which we are indebted to the United States." He will remember, moreover, that while he was sojourning in the United States he sought and obtained opportunities from Prof. Henry to observe the operation of the steam-siren in the lighthouse at Sandy Hook. At that time, if not before, he was made acquainted with the progress not only of American science but also of American art under this head. And in view of the fact that, as the "scientific adviser" of the Elder Brethren of the Trinity House, he has counseled them to discard their English horns and whistles and to substitute for them the steam-sirens which have been, for several years, in the use of our American lighthouses, it would seem that the second branch of the claim advanced by the board at Washington stands in as little need as the first of any additional reënforcement at our hands. Bacon rejoiced in the fact that his philosophy was a philosophy which brought forth fruit in the service of man. The progress of American science in this department has been constantly bearing fresh fruit in the interests of commerce and for the relief of the mariner. Daboll's trumpet, an American invention, came to supersede the use of gongs, and bells, and horns, and guns. To-day the steam-siren, an instrument devised and perfected under the direction of the United States Lighthouse Board, is acknowledged to be without a rival as an efficient fog-signal.

It is no part of our present purpose to institute a critical inquiry into the conflicting views of Prof. Henry and of Prof, Tyndall with regard to the hypotheses respectively espoused by each for the explanation of the phenomena of sound in its passage through wide tracts of air. Prof. Henry believes that the direction and the rate of wind-currents are important elements in the problems presented by the phenomena in question. Prof. Tyndall admits that "the well-known effect of the wind is exceedingly difficult to explain," but he insists on making up the fagot of his scientific opinions on the subject at once and forever without taking the "viewless winds" into his account. He finds a sufficient explanation of all the abnormal phenomena in the assumption of ideal clouds of vapor mingling with the atmosphere so as to disturb its homogeneity, and thereby to quench the body of sound. There is nothing in the working hypothesis of Prof. Henry which excludes any truth there may be in the working hypothesis of Prof. Tyndall. But, in the present provisional state of his inquiries on the subject, the former is disposed to question the sufficiency of the explanation adduced by the latter as an efficient cause of all the phenomena in question. With the modesty and reserve of the true physical philosopher, in the present unfinished state of scientific inquiry, Prof. Henry waits for the wider knowledge which