|Spanish translation & annotations|
Mr. C. P. Patterson
Supt. U. S. Coast Survey
Washington D. C.
In further reply to your letter of the 29 ulto. I beg to submit a brief memorandum of the purpose of my proposed visit to Europe this fall.
The chief object of going is to attend a meeting of the International Geodetical Association at Stuttgart. This association as you are aware is an official union of the chief great national surveys of the world. Its meetings are of a strictly practical character and its proceedings resemble those of a committee: very few papers are read; but a programme is previously made out of the various points concerning the work of the great surveys in regard to which it is supposed that greater accuracy or economy may be attained by means of mutual discussion. Each of these points is taken up in turn and is carefully considered in detail
with a view of effecting the action of different surveys.
In regard to some matters upon which uniformity of methods is particularly desirable, resolutions are passed recommending the use of such methods. Upon other subjects the upshot of the discussion is simply to inform the different surveys and effect their action separately. Although our Coast Survey has never officially entered into this union it has been represented at several of the meetings and its representatives have been cordially received and their presence there has been greatly to the advantage not only of the Coast Survey but also of the general interest of geodesy.
In the Autumn of eighteen hundred seventy five when I was upon the continent of Europe charged with establishing comparisons between values of the force of gravity upon that continent, and in America, by means of pendulum experiments, I had the honor of attending a meeting of the union and of its standing committee by the express invitation of the President. The methods of the pendulum experiments were then discussed at great length, the discussion occupying three days, and the association expressed by resolution their sense of the importance of the comparisons upon which I was then engaged, in
consequence of the action of the Coast Survey, it was determined that all the different surveys should oscillate their pendulums at Berlin for the purpose of comparison. Some of the surveys have already done so, and it is expected that the others will take the same course at the earliest opportunity.
The result of these comparisons has been to show that a great discrepancy exists between the values derived from experiments with the reversible pendulum which for the last twenty years has been exclusively employed, and the method of Bessel, which is believed to be of the highest degree of accuracy.
All attempts at explaining this discrepancy had failed until I announced that it was simply due to the flexure of the tripod upon which the pendulum rests, a source of error from which the method of Bessel is free.
During my stay at Berlin, an experiment exhibiting this effect was shown to His Excellency, Lieut. Gen.l Baeyer and a party of savans assembled for the purpose. The proposed explanation has been regarded with favor by some of the highest authorities in Europe, but the different surveys whose work appears to be vitiated by this cause are naturally reluctant to
admit without the completest demonstration that so many years work is subject to so enormous an error.
At the last meeting of the Union in Brussels, my views were discussed at considerable length, but no conclusion was arrived at, in consequence of there being no one present who was prepared to give an account of the details of my work. The representatives of the Swiss and Austrian surveys, however, who are among the most influential in this matter, adduced experiments of their own which seemed to them to show that no such error affects their work, although in my opinion, it can be shown that the experiments in question do not bear out this conclusion. And indeed there can be no doubt that if this source of error exists at all, the work of these surveys is not free from it.
In consequence of the lack of information in regard to the investigations of the Coast Survey, I have subsequently been requested to send to the Union a complete account of what I have done, and I consequently drew up an extended memoir in the French language which you were so good as to forward to the Union for publication. This memoir contains First, direct measurements of the
flexure of the Coast Survey tripod under the influence of a constant force at different stations.
Second, a conformation of this result by means of a measurement of the consequent twisting of the tripod.
Third, measurements of the oscillations of the tripod caused by the movement of the pendulum itself which are shown by calculation to agree in amount with the values deduced from the observation under the first head.
Fourth, determinations of the force of gravity at New York, making use of two different supports for the pendulum, together with the demonstration that the difference is precisely such as my theory requires.
This paper will be read at the coming meeting of the union and will undoubtedly excite discussion. There are persons of weight upon both sides of the question at issue.
But since a scientific proposition cannot be considered as settled or certain, so long as competent persons doubt it, it is very much to be desired that this discussion should be thoroughly intelligent and should go to the bottom of the subject, which it would be much more likely to do in case
I were present to uphold my views of the matter.
Since this paper was forwarded, I have obtained further confirmation of the truth of my theory. The force of gravity at Berlin is determined by Bessel by methods not subject to this error, and it has since been determined by several modern observers, myself among the number, by the modern methods in question. All the modern results have an approximate agreement, they having been made with instruments nearly similar.
The result of Bessel differs from these by no less than two tenths of a millimeter, a quantity far beyond the limits of admissible error. I now find that by applying the correction due according to me to the flexibility of the stand, the corrected result agrees precisely with that of Bessel to the fifth place of decimals. This important fact should by all means be communicated to the Union, even if we are not to have any representative at the meeting.
The discussion which is to take place upon this subject at Stuttgart will be of the utmost importance to the economy of the pendulum operations at the Coast Survey.
In case it can be shown I am wrong, of which I have little fear, it will follow that methods may be used without scruple which have the advantage of convenience and cheapness, but which must be rejected if my views are confirmed.
On the other hand, should my theory (as I confidently anticipate in case I am present) receive the unanimous sanction of the savans assembled at Stuttgart, the question will immediately arise what sort of supports should be used for the pendulum with a view of combining accuracy with economy. This is a subject upon which it is of the utmost importance for us to have the benefit of the ideas and learning of the gentlemen who will there take part in the discussion, and if we are not represented there, it must almost inevitably follow that our instruments for the future will be inferior to the reformed ones which their ingenuity will devise.
For it would be in the highest degree presumptuous for any one person in such an emergency to suppose that his individual ideas will equal in value those which will emerge from the combined councils of the world.
I therefore conceive it to be of unusual practical importance that the Coast Survey should be represented at this particular meeting. The memoir by me which is to be read there has already passed through your hands. I will send you at the earliest opportunity another copy of it.
The benefits to be derived from the meeting at Stuttgart spring chiefly from the oral discussion which will take place there upon questions upon which the mind of no member is fully made up at the outset, so that their ideas can not appear in the form of written memoirs.
There is another purpose to be fulfilled by a visit to Germany at this time which of itself in my opinion would justify my being sent there. I have now completed the comparison of the force of gravity at European and American stations, but these comparisons depend upon the invariability of the length of the standard meter bar, which has been made use of throughout the investigations.
At the commencement of the experiments this meter was compared with the normal meter at Berlin, and it is essential to the perfection of my
work that it should be recompared at the end of the experiments in order to show that it has sustained no alteration of length either from shocks in the course of transportation, or from those molecular changes which bars are continually undergoing and which have been known to vitiate measurements made with them. Such a comparison must be made before the work is considered as complete, and every year that it is put off increases the danger of changes in its length which would throw an uncertainty upon operations otherwise worthy of high confidence.
I should therefore propose in case of its being adjudged advisable for me to attend the Stuttgart meeting, on my return to remain in Berlin two or three weeks in order to make these necessary comparisons.
Yours very respectfully,
C. S. Peirce
Transcription by Max Fisch, revised by Sara Barrena (2017)
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Proyecto de investigación "La correspondencia del tercer viaje europeo de Charles S. Peirce (septiembre-noviembre 1877)"
Fecha del documento: 10 de octubre 2017
Última actualización: 16 de octubre 2017