Page:Popular Science Monthly Volume 8.djvu/493

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HE work of Prof. Tyndall on the philosophy of sound has won for itself, in its former editions, the highest possible recognition among scientific men, not only in England, but in other countries. A little more than a year ago, the second edition of this book was translated into German under the special supervision of such eminent investigators as Helmholtz and Wiedemann. In the work before us we have the third revision of the eminent professor's observations under this head. In preparing it, he says, he has subjected the previous edition to a careful reexamination, and, in so doing, has "amended as far as possible its defects of style and matter, and paid at the same time respectful attention to the criticisms and suggestions which the former editions called forth."

In the preface to this publication it is announced by Prof. Tyndall that the new matter of greatest importance which has been introduced into it is an account of an investigation which during the past two years he has been conducting in connection with the Elder Brethren of the Trinity House. It may not be known to all our readers that what we call our Lighthouse Board at Washington is known in England as "The Trinity House." The title carries us back to the era when monasticism was prevalent in Europe. In its original charter, the body was named "The Masters, Wardens, and Assistants of the Guild, Fraternity, or Brotherhood of the most Glorious and Undivided Trinity, and of St. Clement, in the Parish of Deptford Stroud, in the County of Kent." In the year 1836, an act of Parliament vested in this "Trinity House," as then constituted, the entire control of the lighthouses of England and Wales, and gave it certain powers over the lights in Scotland and Ireland. Prof. Tyndall appears to have entered on his duties as "the scientific adviser" of the Elder Brethren shortly after his return to England at the close of his lecturing tour in the United States in the year 1873. In the seventh chapter of the present volume, under the head of "Researches on the Acoustic Transparency of the Atmosphere in Relation to the Question of Fog-Signaling," he gives the processes and the results of some very interesting observations which he has conducted under the patronage of the British Trinity House. The general results of these observations had already transpired, but in the work before us they have received the professor's definite statement side by side with a narrative of the researches from which they have been deduced. It is to this portion of the volume, containing "the new matter of greatest importance," that we propose to confine our attention in this short review.