Popular Science Monthly/Volume 8/February 1876/The Controversy on Acoustical Research
TYNDALL ON SOUND.
THE 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.
The reader who turns to this seventh chapter will find that it opens with an "introduction" professing to give "a summary of existing knowledge" in the matter of fog-signaling. The writer states that while the velocity of sound has formed the subject of repeated and refined experiments by the ablest philosophers, "the publication of Dr. Derham's celebrated paper in the 'Philosophical Transactions' for 1708 marks the latest systematic inquiry into the causes which affect the intensity of sound in the atmosphere." And, after making this statement, the professor immediately adds as follows: "Jointly with the Elder Brethren of the Trinity House, and as their scientific adviser, I have recently had the honor of conducting an inquiry designed to fill the blank here indicated." In order still further to impress on the reader a sense of the magnitude of this "blank," Dr. Tyndall indulges in one or two preliminary references which, he says, "will suffice to show the state of the question when this [his] investigation began." The first of these references cites the opinion of Sir John Herschel to the effect that fogs and falling rain, and more especially snow, had been found by Derham "to tend powerfully to obstruct the propagation of sound." The second of his references is made to what he calls "a very clear and able letter" addressed by Dr. Robinson, of Armagh, to the British Board of Trade in 1863. In this "very clear and able letter" Dr. Robinson states that sound is the only known means for coping with fogs, but about it, he adds, "the testimonies are conflicting, and there is scarcely one fact relating to its use as a signal which can he considered as established." But Dr. Robinson is clear on one point—to wit, that "fog is a powerful damper of sound."
On the strength of these historical references, Dr. Tyndall ventures the remark that, prior to the investigation conducted by him, the views enunciated under this head by Derham, Herschel, and Robinson, "were those universally entertained." It was in order to fill "the blank" indicated by the universal prevalence of such erroneous opinions that his inquiry, he says, was set on foot. And his inquiry, he tells us, was begun May 19, 1873.
Now, it is a matter, not only of scientific knowledge, but of public notoriety in this country, that extensive researches on "the causes which affect the intensity of sound in the atmosphere" had been made by the United States Lighthouse Board long before Prof. Tyndall began his investigations. That he should have chosen to ignore the fact in the body of his present volume becomes only the more surprising when, on turning to its preface, we find that be was, as he confesses, "quite aware in a general way that labors, like those now for the first time made public, had been conducted in the United States," and "this knowledge," he subjoins, "was not without influence upon my conduct." If his knowledge of the similar labors conducted under this head in the United States was not, as he acknowledges, without influence on his conduct in giving direction to his researches, it will naturally occur to ordinary minds that this knowledge should also have been "not without influence" on his pen when he was professing to give a summary of the existing state of science on this subject. And when to this statement of the case, as acknowledged by himself, we add that he was made acquainted with the nature and purport of Prof Henry's explorations on this question, not only "in a general way," but also in a very special way, it becomes still more inexplicable that, in defining "the blank" which he claims to have filled by his recent inquiry, he should have disregarded the labors and results of American science, and that, too, while profiting by the instruments and methods of that science in the very conduct of his investigations. The reader will understand the force of our remark that Prof. Tyndall was acquainted with the researches of Prof. Henry, not only "in a general way," but also in a special way, when we state that a paper by the latter—on the abnormal phenomena of sound in relation to fog-signaling—was read by its author in the hearing of Prof. Tyndall at a meeting of the Washington Philosophical Society, called for the purpose of doing honor to the British savant while he was sojourning in the national capital. And the force of our remark that he has ignored the results of American science in magnifying "the blank" which he describes, while profiting by the instruments and methods of that science in conducting his inquiry, will be understood when we say that the researches of Prof. Tyndall were prosecuted with the help of a steam-siren, gratuitously lent to him by the Lighthouse Board at Washington, constructed and patented by a citizen of Mew York, and introduced by Prof. Henry into the lighthouse system of the United States.
We are now prepared for the next stage of this review. It so happened that while Prof. Tyndall was conducting his researches on sound in relation to fog-signaling, an officer of the United States Corps of Engineers, Major Elliot, had been deputed by the Lighthouse Board at Washington to make a tour of inspection in Europe, with instructions to report upon matters relative to lighthouse apparatus and the management of lighthouse systems. Major Elliot reached London a few days before Prof. Tyndall began his experiments at Dover, and was courteously invited to be present, but for want of time was compelled to forego the privilege. The results of the English experiments were, however, subsequently communicated to Major Elliot by Sir Frederick Arrow, the Deputy Master of Trinity House (who, we are sorry to say, has since deceased), and were embodied in his report on the "European Lighthouse Systems," as recently published. The publication of Major Elliot's report was accompanied, in the annual report of the United States Lighthouse Board for the year 1874, with the following observations:
"Major Elliot gives a detailed account of a late series of experiments by the
Trinity House Board on fog-signals. Now, although this account is interesting in itself to the public generally, yet, being addressed to the Lighthouse Board of the United States, it would tend to convey the idea that the facts which it states were new to the board, and that the latter had obtained no results of a similar kind; while a reference to the Appendix to this report will show that the researches of our Lighthouse Board have been much more extensive on this subject than those of the Trinity House, and that the latter has established no facts of practical importance which had not previously been observed and used by the former."
The "Appendix" here referred to is from the pen of Prof. Henry, the chairman of the board, and details elaborate experiments on sound in relation to fog-signaling, as pursued in the service of the United States Lighthouse Board since the year 1855. Brought to book by this "Appendix," Prof. Tyndall asks his readers, in the preface of the present edition of his volume, to bear in mind that "the Washington Appendix was published nearly a year after his [my] report to the Trinity House." But in so writing it seems to have escaped his notice that in a subsequent part of this same preface he has confessed that he was "quite aware in a general way" that labors like his own had been conducted in the United States, and that "this knowledge was not without influence on his conduct." And in so writing he forgets, too, that he was an interested listener to the paper read by Prof. Henry on this subject in his hearing while he was in the United States, and before he had turned any attention at all to the phenomena of sound in connection with fog-signals. He states in the body of his book, as already mentioned, that his inquiry under this head began on May 19, 1873, several months after his "general" and his special knowledge of what had been accomplished in this country. And yet, in the face of all these facts and acknowledgments he has allowed his "summary of existing knowledge" on the subject to stand without any recognition of American science in the premises—a suppression which does as little credit to his scientific generosity as to his literary art, for he can be convicted of delinquency in respect of the former by the inconsistency of statement into which he has fallen through a want of dexterity in the latter.
We may, therefore, safely leave the acknowledged record to substantiate the claims of the United States Lighthouse Board when they represent that their researches, running through many years, "are much more extensive on this subject than those of the Trinity House." It remains for us only to consider the second branch of their representation—namely, that the latter (the Trinity House) "has established no facts of practical importance which had not been previously observed and used by the former (the United States Lighthouse Board)." In support of this statement we may point to the fact that Prof. Tyndall nowhere pretends to have established by his researches any improvements whatsoever on the methods or instruments 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 shall furnish the basis of an assured induction meeting all the requirements of the problem.
Prof. Tyndall, however, is impatient of any contradiction. He admits that he has not verified the effect of wind-currents "by means of a captive balloon rising high enough to catch the deflected wave," but none the less he ventures to propound his hypothesis as the last word of science in the premises. Indeed, he takes great credit to himself for having been able to rise above "the authority" of Prof. Henry in this investigation. He says that in one of his "phases of thought" on the question he passed through the solution "which Prof. Henry now offers for acceptation," "weighed it in the balance," and "found it wanting." And, as if this language were not supercilious enough, he proceeds to indulge in the following self-complacent reflections:
"But though it [Prof. Henry's solution of ocean-echoes] thus deflected me from the proper track, shall I say that authority in science is injurious? Not without some qualification. It is not only injurious, but deadly, when it cows the intellect into fear of questioning it. But the authority which so merits our respect as to compel us to test and overthrow all its supports, before accepting a conclusion opposed to it, is not wholly noxious. On the contrary, the disciplines it imposes may be in the highest degree salutary, though they may end, as in the present case, in the ruin of authority."
It is impossible to conceive of language more expressive of vanity, conceit, and arrogance, than this ascription of intellectual superiority to which Prof. Tyndall treats himself on the assumption that he has laid "the authority" of Prof. Henry in "ruins" upon the question of atmospheric sound. At no time and in no place has Prof. Henry assumed to speak "by authority" on the subject. The man of straw whom Tyndall sets up under cover of Henry's name, in order to exhibit upon it the strength and prowess of his intellectual muscle, is a cheap device of rhetoric which a much inferior man might have disdained to employ in a case like this. The cause of science does not profit by the self-laudation of its votaries, and Prof. Tyndall's praises are in the mouths of too many people to render it necessary for him to praise himself at the expense of Prof. Henry or of anybody else.
REPLY OF PROFESSOR TYNDALL.
To the Editor of the Nation.
Sir: I have been favored with a copy of the Nation of October 8th, and would ask permission to make a few remarks on the critique of my work on "Sound" therein contained.
With regard to Prof. Henry, I hope I am not presumptuous in venturing the opinion, and expressing the belief, that his earlier scientific labors were marked by rare power and originality, and that his later years have been usefully and honorably employed in the service of his country. Such, if I dare say so, are the sentiments which I have ever expressed regarding Prof. Henry here and elsewhere.
When I first learned that he was in danger of falling into what I considered to he grave scientific error, I went as far as friendliness dared go to avert it. I addressed to him a private letter, in which I tried to impress upon him the completeness and conclusiveness of the evidence which he seemed disposed to call in question. He did not honor that letter with any notice, preferring to discuss the subject publicly in the "Report of the Washington Lighthouse Board." He was clearly within his right in doing so; but I submit that I only exercised my right when I met him on ground thus chosen by himself.
No English gentleman that I have consulted can discern in what I have written any violation of the dignity of scientific debate; but your article would lead to the inference that I had both violated common honesty and taken leave of common-sense. I will not quote your words, because I cherish the hope that when you have reflected on them you will regret them. When I say "you," I mean the editor of the Nation, whose acquaintance I had the honor to make, and whose kindness I had the privilege to experience, in New York—I do not mean the writer of the article. Let me respectfully assure you, then, that, when I spoke of being "deflected by authority," "Prof. Henry's solution of ocean-echoes" was not at all in my mind, nor his "ruin," partial or total, in my calculations. Consider, I pray you, how impossible it is that this could have been the case. The "deflection" spoken of is expressly described as occurring at the outset of an investigation begun in May, 1873, whereas the Washington report containing Prof. Henry s solution of ocean-echoes is the report for 1874, which did not reach Europe until the spring of 1875. This, then, is the crumbling foundation on which your critic builds his odious charge. In verity, the remark on which he pours his peroratory invective was not meant for "laudation" of any kind, but merely to show the "polar" character of authority—its good side and its bad.
It is easy, as you know, Mr. Editor, to sneer and to assail; but less easy to show, without going into details not worth the labor, that the sneer is unmeaning, and the assault unfair. Nevertheless, the broad lines on which, in the present instance, I would meet my anonymous assailant may, I think, be made clear. He industriously mixes together things which ought to be kept apart—experiments on fog-signals and inquiries into "the causes which affect the transmission of sound through the atmosphere." The "blank" which I proposed to fill is stated, with unmistakable clearness, to have reference solely to such "causes." Neither Herschel nor Robinson, as far as I know, ever made an experiment on fog-signals; still I quote them. Why? Because they are the most eminent and authoritative exponents of the theories of acoustic opacity which up to last year were entertained by the highest scientific minds. Theirs, moreover, and Arago's (not Prof. Henry's), was the "authority" which "deflected" me at first. Apart from the wind, the "causes" of acoustic opacity indorsed by these eminent men were rain, hail, snow, haze, and fog—everything, in short, that affected the optical clearness of the atmosphere. Prior to the South Foreland investigation, where, I would ask, is a "systematic inquiry" into these causes to be found? Surely, if such an inquiry has been published, it can be courteously pointed out and calmly discussed. If you can prove its existence you will have the right to demand from me the very fullest apology and reparation for stating that "no such systematic inquiry had to my knowledge been made." Even then I could not charge myself with untruth; for my "knowledge" was, and is, arithmetically what I have affirmed it to be; but I can confess ignorance and express regret.
Give me your patience while I endeavor still further to make this matter clear. As regards the invention of instruments and their practical establishment as fog-signals, so far was my knowledge behind "the science of the United States," that I had never seen or heard one of those great steam-whistles until I met them at the South Foreland. The common "siren" is well known to have been a familiar instrument with me, but the fog-signal I first saw and heard upon its native soil in America—not, however, as your critic puts it, but at the request, twice repeated, of Prof. Henry. Further, to the best of my recollection, prior to the month of May, 1873, I had only heard one or two experimental blasts from a fog-trumpet. In such work, then, I had neither part nor lot; and, if you will permit me to say so, though it is of the utmost practical value, I should hardly label such work with the name of "science." Quite apart from those practical achievements lies the inquiry into "the causes which affect the transmission of sound through the atmosphere." And, if I except the sagacious remark of General Duane which has been so curtly brushed aside, not a scintilla of light has been cast upon these causes by any researches ever published by the Lighthouse Board of Washington.
Will you allow me to say, in passing, that Major Elliot, the able and conscientious officer whose excellent "Report on the Lighthouses of Europe" was so displeasing to the board, did accept the invitation to Dover, and that to the present hour I feel indebted to him for the information and advice given to me at the time?
Upon my "conduct" and the knowledge which "influenced" it, your critic rings the changes of his wit. It is, after all, a very simple and straightforward matter. The "conduct" consisted in my emphatic advice to the Elder Brethren of the Trinity House not to confine themselves to home-made apparatus, but to include American ones in their inquiry. The subsequent trial led to the abandonment of the English instruments, and the adoption of others from Canada and the United States. The siren, for example—which your critic erroneously says was lent "gratuitously" to me—was paid for in February, 1874, and two others are at this moment on their way from New York to England. Both by word and deed have we acknowledged our real obligations to the United States; but what we did not and could not acknowledge (for it was non-existent) was, any solution of the conflicting and anomalous results obtained with these fog-signals—results so conflicting and so anomalous as to cause reflecting minds to entertain doubts as to the capacity of the observers. Apart from the friendship shown to me at the time, all that I remember of the meeting at Washington, to which your critic refers, is the utter perplexity of everybody present, myself included, in regard to the matter in hand. I had my guess—others had theirs; but we were quite at sea in our guesses, without a signal to guide us through the intellectual fog.
Knowing, indeed, the difficulty of the subject, when its investigation was first proposed to me by the Elder Brethren, I shrank (as Faraday had done before me) from a work of such obvious labor and such uncertain scientific promise. Doggedly, however, we attacked it, determined to go through the mechanical processes already followed by others, even if they led, as regards science, to an equally barren result. Out of the darkness at length came the dawn. We prolonged our investigations until they embraced every agent, save one, to which influence had been previously ascribed. The exception was snow. This, however, was directly met by observations made upon the Mer de Glace in the bitter winter of 1859, and which have been entirely confirmed by the later observations of General Duane. Having negatived antecedent theories, we wrought our way positively to the basis of the whole question. This we found in a cloud-world, invisible to the eye of sense, but as visible and certain to the mental eye as the ordinary cloud-world of our atmosphere. The lights and shadows of these "acoustic clouds"—the action of which must, at one time or another, have been noticed by every peasant within range of a peal of bells—sufficed to account for the most astounding variations of intensity. This, I say, has been established, not only by patient and long-continued observations afloat, but by laboratory experiments as indubitable as any within the range of physical science.
And, let me add, it was neither whistles nor trumpets, nor yet the siren, which pointed out the way to this solution, but experiments with guns ably served by artillerymen from Dover Castle.
I will not make any further draft upon your generosity, though, were it worth while to do so, other fallacies of fact and logic in your critic's article might be exposed. He says, or intimates, for example, that I became "adviser" to the Trinity House after my "lecturing tour in the United States in 1873." I relieved Michael Faraday of this duty in May, 1866. My friends in New York have already had to disperse other delusions regarding the "profits" of that "tour." Such statements are credible to the mean, incredible to the high-minded, and were therefore never thought worthy of refutation by me. And why should I now waste a word upon your critic's closing sentences? It will not make him noble to be told that envy is ignoble; that, if ever "praise" has been adjudged to me by his country-men, it is not because I went out of my way to seek it. It came to me unasked—an incident, not an aim—shining, as your own Emerson would put it, pleasantly because spontaneously, upon the necessary journey of my life. It was not, I can truly say, the applause of large assemblies that constituted my chief happiness in the United States, but the ever-growing proof, for the most part undemonstrative, that, without swerving from my duty, I had gained a modicum of the affection of the American people. That I prized, and that I have sought to keep free from fleck, material or intellectual. For reasons best known to himself, your critic does not relish this relation; and he will damage it if he can, I cherish the belief that he will be unsuccessful.I have the honor to be, your obedient servant,
London, November 23, 1875.