Popular Science Monthly/Volume 3/October 1873/The Glaciers and their Investigators
| THE GLACIERS AND THEIR INVESTIGATORS. |
By Prof. JOHN TYNDALL.
SOON after my return from America, I learned with great concern that a little book of mine, published prior to my departure, had given grave offence to some of the friends and relatives of the late Principal Forbes; and I was specially grieved when informed that the chastisement considered due to this offence was to be administered by gentlemen between whom and myself I had hoped mutual respect and amity would forever reign. We had, it is true, met in conflict on another field; but hostilities had honorably ceased, old wounds had, to all appearance, been healed, and I had no misgiving as to the permanence of the peace established between us.
The genesis of the book referred to is this: At Christmas, 1871, it fell to my lot to give the brief course of "Juvenile Lectures" to which Faraday for many years before his death lent such an inexpressible charm. The subject of glaciers, which I had never previously treated in a course of lectures, might, it was thought, be rendered pleasant and profitable to a youthful audience. The sight of young people wandering over the glaciers of the Alps with closed eyes, desiring knowledge, but not always finding it, had been a familiar one to me, and I thought it no unworthy task to respond to this desire, and to give such of my young hearers as might visit the Alps an intelligent interest in glacier phenomena.
The course was, therefore, resolved upon; and, to render its value more permanent, I wrote out copious "Notes," had them bound together, and distributed among the boys and girls. Knowing the damage which elementary books, wearily and confusedly written, had done to my own young mind, I tried, to the best of my ability, to confer upon these "Notes" clearness, thoroughness, and life. It was my particular desire that the imaginary pupil chosen for my companion in the Alps, and for whom, odd as it may sound, I entertained a real affection, should rise from the study of the "Notes" with no other feeling than one of attachment and respect for those who had worked upon the glaciers. I therefore avoided all allusion to those sore personal dissensions which, to the detriment of science and of men, had begun fifteen years prior to my connection with the glaciers, and which have been unhappily continued to the present time.
Prof. Youmans, of New York, was then in London, organizing the "International Scientific Series," with which his name and energy are identified. To prove my sympathy for his work, I had given him permission to use my name as one of his probable contributors, the date of my contribution being understood to belong to the distant, and indeed indefinite, future. He, however, read the "Notes," liked them, urged me to expand them a little, and to permit him to publish them as the first volume of his series. His request was aided by that of another friend, and I acceded to it—hence the little book, entitled the "Forms of Water," which the friends and relatives of Principal Forbes have read with so much discontent.
That modest volume has, we are informed, caused an uncontemplated addition to be made to the Life of Principal Forbes, lately published under the triple auspices of Principal Shairp, the successor of Principal Forbes in the College of St. Andrew's, Mr. Adams-Reilly, and Prof. Tait. "It had been our hope," says Principal Shairp, in his preface, "that we might have been allowed to tell our story without reverting to controversies which, we had thought, had been long since extinguished. But, after most of these sheets were in press, a book appeared, in which many of the old charges against Principal Forbes in the matter of the glaciers were, if not openly repeated, not obscurely indicated. Neither the interests of truth, nor justice to the dead, could suffer such remarks to pass unchallenged. How it has been thought best for the present to meet them, I must leave my friend and fellow-laborer, Prof. Tait, to tell."
The book here referred to is the unpretending volume whose blameless advent I have just described.
I have not the honor of knowing Principal Shairp personally, but he will, I trust, permit me to assure him of two things: Firstly, that, in writing my book, I had no notion of rekindling an extinct fire, or of treating with any thing but tenderness the memory of his friend. Secondly, that, had such been my intention, the negative attribute, "not obscure," is hardly the one which he would have chosen to describe the words that I should have employed. But the fact is, the fire was not extinct: the anger of former combats, which I thought spent, was still potential, and my little book was but the finger which pulled the trigger of an already-loaded gun.
Let the book speak for itself. I reproduce here in extenso the references to Principal Forbes, which have been translated into "charges" against him by Principal Shairp. Having, in section 20, mentioned the early measurements of glaciers made by Hugi and Agassiz, I continue thus:
"A great step is here gained. You notice that the middle numbers are the largest. They correspond to the central portion of the glacier. Hence, these measurements conclusively establish, not only the fact of glacier motion, but that the centre of the glacier, like that of a river, moves more rapidly than the sides.
"With the aid of trained engineers, M. Agassiz followed up these measurements in subsequent years. His researches are recorded in a work entitled 'Système Glaciaire,' which is accompanied by a very noble Atlas of the Glacier of the Unteraar, published in 1847.
"These determinations were made by means of a theodolite, of which I will give you some notion immediately. The same instrument was employed the same year by the late Principal Forbes upon the Mer de Glace. He established independently the greater central motion. He showed, moreover, that it is not necessary to wait a year, or even a week, to determine the motion of a glacier; with a correctly-adjusted theodolite he was able to determine the motion of various points of the Mer de Glace from day to day. He affirmed, and with truth, that the motion of the glacier might be determined from hour to hour. We shall prove this farther on. Prof. Forbes also triangulated the Mer de Glace, and laid down an excellent map of it. His first observations and his survey are recorded in a celebrated book published in 1843, and entitled 'Travels in the Alps.'
"These observations were also followed up in subsequent years, the results being recorded in a series of detached letters and essays of great interest. These were subsequently collected in a volume entitled 'Occasional Papers on the Theory of Glaciers,' published in 1859. The labors of Agassiz and Forbes are the two chief sources of our knowledge of glacier phenomena."It would be difficult for an unbiassed person to find in these words any semblance of a "charge" against Principal Forbes. His friends and relatives may be dissatisfied to see the name of M. Agassiz placed first in relation to the question of the quicker central flow of glaciers; but in giving it this position I was guided by the printed data which are open to any writer upon this subject.
I have checked this brief historic statement by consulting again the proper authorities, and this is the result: In 1841 Principal Forbes became the guest of M. Agassiz on the glacier of the Aar; and in a very able article, published some time subsequently in the Edinburgh Review, he speaks of "the noble ardor, the generous friendship, the unvarying good temper, the true hospitality" of his host. In order to explain the subsequent action of Principal Forbes, it is necessary to say that the kindly feeling implied in the foregoing words did not continue long to subsist between him and M. Agassiz. I am dealing, however, for the moment with scientific facts, not with personal differences; and, as a matter of indisputable fact, M. Agassiz did, in 1841, incur the labor of boring six holes in a straight line across the glacier of the Aar, of fixing in these holes a series of piles, and of measuring, in 1842, the distance through which the motion of the glacier had carried them. This measurement was made on July 20th; some results of it were communicated to the Academy of Science in Paris on August 1st, and they stand in the "Comptes Rendus" of the Academy as an unquestionable record, from which date can be taken.
But the friends quarrelled. Who was to blame I will not venture here to intimate; but the assumption that M. Agassiz was wholly in the wrong would, I am bound to say, be required to justify the subsequent conduct of Principal Forbes. He was, I gather from the Life, acquainted with the use of surveying instruments; and knowing roughly the annual rate of glacier-motion, he would also know that through the precision attainable with a theodolite, a single day's—probably a single hour's motion—especially in summer, must be discernible. With such knowledge in his possession, as early as June, 1842, and without deeming it necessary to give his host of the Aar any notice of his intention, Principal Forbes repaired to the Mer de Glace, made in the first instance a few rapid measurements at the Montanvert, and in a letter dated from Courmayeur, on July 4th, communicated them to the editor of the Edinburgh New Philosophical Journal.
He did not at that time give any numbers expressing the ratio of the side to the central motion of the glacier, but contented himself with announcing the result in these terms: "The central portion of the Mer de Glace moves past the edges in a very considerable proportion, quite contrary to the opinion generally entertained." This communication, as I have said, bears the date of July 4th; but it was first published in the October number of the journal to which it was addressed. My reason, therefore, for mentioning Agassiz first in the "Forms of Water" is, that, apart from all personal complications, his experiment was begun ten months prior to that of his rival, and that he had also two months' priority of publication.
Neither in his "Travels in the Alps," nor in his "Occasional Papers," does Principal Forbes, to my knowledge, make any reference to this communication of Agassiz. I am far from charging him with conscious wrong, or doubting that he justified this reticence to his own mind. But my duty at present lies with objective facts, and not with subjective judgments. And the fact is that, for eighteen years subsequent to this campaign of 1842, Agassiz, as far as the glaciers are concerned, was practically extinguished in England. The labors of the following years failed to gain for him any recognition. His early mistake regarding the quicker motion of the sides of a glacier, and other weaknesses, were duly kept in view; but his positive measurements, and his Atlas, which prove the observations upon the glacier of the Aar to be far more complete than those made upon any other glacier, were never permitted to yield the slightest credit to their author. I am no partisan of Agassiz, but I desire to be just.
Here, then, my case ends as regards the first reference to Principal Forbes, in section 20 of the "Forms of Water."
In section 48 I describe the dirt-bands of the Mer de Glace, and ascribe the discovery of them to Principal Forbes. There can be no thought of a "charge" here.
The next reference that has any bearing upon this discussion occurs in sections 59 and 60 of the "Forms of Water." I quote it fully:
"Still the idea found its advocates. In a little book, published in 1773, and entitled 'Picturesque Journey to the Glaciers of Savoy,' Bordier, of Geneva, wrote thus: 'It is now time to look at all these objects with the eyes of reason; to study, in the first place, the position and the progression of glaciers, and to seek the solution of their principal phenomena. At the first aspect of the ice mountains an observation presents itself, which appears sufficient to explain all. It is that the entire mass of ice is connected together, and presses from above downward after the manner of fluids. Let us, then, regard the ice, not as a mass entirely rigid and immobile, but as a heap of coagulated matter, or as softened wax, flexible and ductile to a certain point.' Here probably for the first time the quality of plasticity is ascribed to the ice of glaciers.
"To us, familiar with the aspect of the glaciers, it must seem strange that this idea once expressed did not at once receive recognition and development. But in those early days explorers were few, and the 'Picturesque Journey' probably but little known, so that the notion of plasticity lay dormant for more than half a century. But Bordier was at length succeeded by a man of far greater scientific grasp and insight than himself. This was Rendu, a Catholic priest and canon when he wrote, and afterward Bishop of Annecy. In 1841 Rendu laid before the Academy of Sciences of Savoy his 'Theory of the Glaciers of Savoy,' a contribution forever memorable in relation to this subject.
"Rendu seized the idea of glacier plasticity with great power and clearness, and followed it resolutely to its consequences. It is not known that he bad ever seen the work of Bordier; probably not, as he never mentions it. Let me quote for you some of Rendu's expressions, which, however, fail to give an adequate idea of his insight and precision of thought: 'Between the Mer de Glace and a river there is a resemblance so complete that it is impossible to find in the glacier a circumstance which does not exist in the river. In currents of water the motion is not uniform, either throughout their width or throughout their depth. The friction of the bottom and of the sides, with the action of local hindrances, causes the motion to vary, and only toward the middle of the surface do we obtain the full motion.'
"This reads like a prediction of what has since been established by measurement. Looking at the glacier of Mont Dolent, which resembles a sheaf in form, wide at both ends and narrow in the middle, and reflecting that the upper wide part had become narrow, and the narrow middle part again wide, Rendu observes: 'There is a multitude of facts which seem to necessitate the belief that glacier-ice enjoys a kind of ductility, which enables it to mould itself to its locality, to thin out, to swell, and to contract, as if it were a soft paste.'
"To fully test his conclusions, Rendu required the accurate measurement of glacier motion. Had he added to his other endowments the practical skill of a land-surveyor, he would now be regarded as the prince of glacialists. As it was, he was obliged to be content with imperfect measurements. In one of his excursions he examined the guides regarding the successive positions of a vast rock which he found upon the ice close to the side of the glacier. The mean of five years gave him a motion for this block of forty feet a year.
"Another block, the transport of which he subsequently measured more accurately, gave him a velocity of 400 feet a year. Note his explanation of this discrepancy: 'The enormous difference of these two observations arises from the fact that one block stood near the centre of the glacier, which moves most rapidly, while the other stood near the side, where the ice is held back by friction.' So clear and definite were Rendu's ideas of the plastic motion of glaciers, that, had the question of curvature occurred to him, I entertain no doubt that be would have enunciated beforehand the shifting of the point of maximum motion from side to side across the axis of the glacier (§25).
"It is right that you should know that scientific men do not always agree in their estimates of the comparative value of facts and ideas; and it is especially right that you should know that your present tutor attaches a very high value to ideas when they spring from the profound and persistent pondering of superior minds, and are not, as is too often the case, thrown out without the warrant of either deep thought or natural capacity. It is because I believe Rendu's labors fulfil this condition that I ascribe to them so high a value. But, when you become older and better informed, you may differ from me; and I write these words lest you should too readily accept my opinion of Rendu. Judge me, if you care to do so, when your knowledge is matured. I certainly shall not fear your verdict.
"But, much as I prize the prompting idea, and thoroughly as I believe that often in it the force of genius mainly lies, it would, in my opinion, be an error of omission of the gravest kind, and which, if habitual, would insure the ultimate decay of natural knowledge, to neglect verifying our ideas, and giving them outward reality and substance when the means of doing so are at hand. In science, thought, as far as possible, ought to be wedded to fact. This was attempted by Rendu, and in great part accomplished by Agassiz and Forbes.
"Here, indeed, the merits of the distinguished glacialist last named rise conspicuously to view. From the able and earnest advocacy of Prof. Forbes, the public knowledge of this doctrine of glacial plasticity is almost wholly derived. He gave the doctrine a more distinctive form; he first applied the term viscous to glacier-ice, and sought to found upon precise measurements a 'viscous theory' of glacier-motion.
"I am here obliged to state facts in their historic sequence. Prof. Forbes, when he began his investigations, was acquainted with the labors of Rendu. In his earliest works upon the Alps he refers to those labors in terms of flattering recognition. But, though, as a matter of fact, Rendu's ideas were there to prompt him, it would be too much to say that he needed their inspiration. Had Rendu not preceded him, he might none the less have grasped the idea of viscosity, executing his measurements, and applying his knowledge to maintain it. Be that as it may, the appearance of Prof. Forbes on the Unteraar Glacier in 1841, and on the Mer de Glace in 1842, and his labors then and subsequently, have given him a name not to be forgotten in the scientific history of glaciers."Here, again, I have to declare that, in writing thus, I had no notion of "raking up" an old controversy. My object was to render my account historically continuous, and there is not a single word to intimate that I took exception to Principal Forbes's treatment of Rendu. Nay, while placing the bishop in the position he merited, I went out of my way to point out that, in all probability, Principal Forbes required no such antecedent. So desirous was I that no unkind or disparaging word should escape me regarding Principal Forbes, that, had a reasonable objection to the phraseology here used been communicated to me by his friends, I should have altered the whole edition of the work sooner than allow the objectionable matter to appear in it. . . . .
My final reference to Principal Forbes was in § 67 of the "Forms of Water," where the veined structure of glacier-ice is dealt with. Its description by Guyot, who first observed it, is so brief and appropriate that I quoted his account of it. But this was certainly not with a view of damaging the originality of Principal Forbes. In paragraph 474 of my book the observation of the structure upon the glacier of the Aar is thus spoken of: "The blue veins were observed independently three years after M. Guyot had first described them. I say independently, because M. Guyot's description, though written in 1838, remained unprinted, and was unknown in 1841 to the observers on the Aar. These were M. Agassiz and Prof. Forbes. To the question of structure, Prof. Forbes subsequently devoted much attention, and it was mainly his observations and reasonings that gave it the important position now assigned to it in glacier phenomena."
This is the account of Guyot's observation given by Principal Forbes himself. But it may be objected that I am not correct in classing him and Agassiz thus together, and that to Principal Forbes alone belongs the credit of observing the veined structure upon the Aar Glacier. This may be true, but would an impartial writer be justified in ignoring the indignant protests of M. Agassiz and his companions? With regard to the development of the subject, I felt perfectly sure of the merits of Principal Forbes, and did not hesitate to give him the benefit of my conviction.
Such, then, are the grounds of Principal Shairp's complaint quoted at the outset—such the "charges" that I have made "against Principal Forbes," and which the "interests of truth" and "justice to the dead" could not "suffer to pass unchallenged." There is, I submit, no color of reason in such a complaint, and it would never, I am persuaded, have been made had not Principal Shairp and his colleagues found themselves in possession of a document which, though published a dozen years ago by Principal Forbes, was never answered by me, and which, in the belief that I am unable to answer it, is now reproduced for my confutation.
The document here referred to appeared soon after the publication of the "Glaciers of the Alps" in 1860. It is entitled "Reply to Professor Tyndall's Remarks in his Work on the 'Glaciers of the Alps, relating to Rendu' s 'Théorie des Glaciers.'" It was obviously written under feelings of great irritation, and, longing for peace, the only public notice I took of it at the time was to say that "I have abstained from answering my distinguished censor, not from inability to do so, but because I thought, and think, that within the limits of the case it is better to submit to misconception than to make science the arena of personal controversy." My critics, however, do not seem to understand that, for the sake of higher occupations, statements may be allowed to pass unchallenged which, were their refutation worth the necessary time, might be blown in shreds to the winds. Of this precise character, I apprehend, are the accusations contained in the republished essay of Principal Forbes, which his friends, professing to know what he would have done were he alive, now challenge me to meet. I accept the challenge, and throw upon them the responsibility of my answer. . . .[1]
Having thus disposed of the two really serious allegations in the reply, I am unwilling to follow it through its minor details, or to spend time in refuting the various intimations of littleness on my part contained in it. The whole reply betrays a state of mental exacerbation which I willingly left to the softening influence of time, and to which, unless forced to it, I shall not recur.
The biographer who has revived this subject speaks of "the numerous controversies into which he" (Principal Forbes) "was dragged." I hardly think the passive verb the appropriate one here. The following momentary glimpse of Principal Forbes's character points to a truer theory of his controversies than that which would refer them to a "drag" external to himself:
"The hasty glance," says this biographer, "which I have been able to bestow upon his less scientific letters has shown me that Forbes attached great importance to mere honorary distinctions, as well as the opinion of others regarding the value of his discoveries. It has opened up a view of a, to me, totally unexpected feature of his character." This is honest, but that the revelation should be "unexpected" is to me surprising. The "love of approbation" here glanced at was in Principal Forbes so strong that he could not bear the least criticism of his work without resenting it as personal. I well remember the late excellent William Hopkins describing to me his astonishment when, at the meeting of the British Association at York, a purely scientific remark of his on Forbes's glacier theory was turned, with sudden acerbity, into a personal matter. It is of a discussion arising out of this remark that Principal Forbes writes thus: "We had a postponed discussion on glaciers on Saturday morning, when Hopkins and I did battle, and I am sorry to say I felt it exceedingly; it discomposed my nerves and made me very uncomfortable indeed, until I was soothed by the minster-service yesterday."[2]
But no amount of "minster-service" could cope with so strong a natural bias, and many a bitter drop fell from the pen of Principal Forbes into the lives of those whom he opposed subsequent to this service at York. On hearing of the paper presented by Mr. Huxley and myself to the Royal Society, he at once jumped to the conclusion that the glaciers were to be made a "regular party question." "All I can do," he says, "is to sit still till the indictment is made out; and I cordially wish my enemy to write a book and print it speedily, as any thing is better than innuendo and suspense."[3] What he meant by "indictment" I do not know; and, with regard to "innuendo," neither of the writers of the paper would be likely to resort to it in preference to plain speaking. The words of a witty philosopher at the time here referred to are significant: "Tyndall," he said, "is beginning with ice, but he will end in hot water." He knew the circumstances, and was able to predict the course of events with the certainty of physical prevision.
The quality referred to by his biographer, and the tendency arising from it to look at things in a personal light, caused his intellect to run rapidly into hypotheses of moral action which had no counterpart in real life. I read with simple amazement his explanation to his friend Mr. Wills of the postponement of the publication of the "Glaciers of the Alps." Some of his supporters in the Council of the Royal Society had proposed him for the Copley Medal, but without success. Had the rules of good taste been observed, he would have known nothing of these discussions; and, knowing them, he ought to have ignored them. But he writes to his friend: "I believe the effect of the struggle, though unsuccessful in its immediate object, will be to render Tyndall and Huxley and their friends more cautious in their further proceedings. For instance, Tyndall's book, again withdrawn from Murray's 'immediate' list, will probably be infinitely more carefully worded relative to Rendu than he first intended."[4]
I should be exceedingly sorry to apply to Principal Forbes the noun-substantive which Byron, in "Childe Harold," applied to Rousseau, but the adjective "self-torturing" is, I fear, only too applicable. His quick imagination suggested chimerical causes for events, but never any thing more chimerical than that here assigned for the postponement of my book and its probable improvement. The "struggle" in the council had no influence upon me, for this good reason, if for no other, that I knew absolutely nothing of the character of the struggle. In Nature, for May 22, 1873, Prof. Huxley has effectually disposed of this hypothesis;[5] and those who care to look at the opening sentences of a paper of mine in Mr. Francis Galton's "Vacation Tourists for 1860," will find there indicated another reason for the delay. I may add, that the only part I ever took in relation to Principal Forbes and a medal was to go on one occasion to the Royal Society with the express intention of recommending that he should have one.
The features of character partly revealed by his biographer also explain that tendency on the part of Principal Forbes to bring his own labors into relief, to the manifest danger of toning down the labors of others. This is illustrated by the foot-note appended to page 419. It is also illustrated by his references to Rendu, which, frequent and flattering as they are, left no abiding impression upon the reader's mind. By some qualifying phrase the quotation in each case is deprived of weight; while practical extinction for eighteen years was, as already intimated, the fate of the "generous" and "hospitable" Agassiz.
Toward the close of the "Life" his biographer, while admitting that "to say that Forbes thoroughly explained the behavior of glaciers would be an exaggeration," claims for him that he must "ever stand forward in the history of the question as one of its most effective and scientific promoters." This meed of praise I should be the last to deny him, for I believe it to be perfectly just. To secure it, however, no bitterness of controversy, no depreciation of the services of others, was necessary. One point here needs a moment's clearing up. The word "theory," as regards glaciers, slides incessantly, and without warning, from one into the other of two different senses. It means sometimes the purely physical theory of their formation, structure, and motion, with which the name of Principal Forbes is so largely identified. But it has a wider sense where it embraces the geological action of glaciers on the surface of the globe. For a long time "glacier theory" had reference mainly to the geological phenomena; it was in this sense that the words were employed by Principal Forbes in his article in the Edinburgh Review, published in 1842. It is in this sense that they are now habitually applied by M. Agassiz, and in relation to the theory thus defined it is no more than natural for his supporters to assign to M. Agassiz the highest place. I mention this to abolish the mystification which threatens to surround a question which this simple statement will render clear.
I trust I may be permitted to end here. Strong reasons may cause me to revert to this question, but they must be very strong. I would only warn my readers against the assumption that, if I do not reply to further attack, I am unable to reply to it. The present rejoinder furnishes sufficient proof of the doubtfulness of such a conclusion. There is one darkly-expressed passage in the "Life of Principal Forbes" which may cover something requiring notice. "We are informed that he preserved and carefully docketed all letters written to him, and that he retained copies of all his own. It is with regard to this correspondence that his biographer writes thus:" Many extracts, and even entire letters, may be selected which are free from controversy, yet in general these would give but an imperfect notion of the import of the whole. Others again cannot be published at present, because the writers supply him with details of that mysterious wire-pulling which seems to be inseparable from every transaction involving honors (scientific, in common with all others, it is humiliating to confess). The value of this unique series is, however, so great, and its preservation so complete, that it is to be hoped it may be safely deposited (under seal) in the care of some scientific society or institution, to be opened only when all the actors have passed from the scene."
These undignified allusions to "wire-pulling" are perfectly dark tome; but if the letter addressed to Mr. Wills may be taken as a specimen of the entire "series," here referred to, then I agree with the biographer in pronouncing it "unique." Would it not, however, be a manlier course, and a fairer one to those who, writing without arrière-pensée retain no copies of what they write, to let them know, while they are here to take care of themselves, how their reputations are affected by these letters of Principal Forbes? For my own personal part I am prepared to challenge the production of this correspondence now.—Contemporary Review.
