Report from Charles S. Peirce on his second European trip for
the Anual Report of the Superintendent
of the U. S. Coast Survey
(New York, 18.05.1877)

Spanish translation & annotations


Assistant C. S. Peirce was instructed early in the spring of 1875 to proceed to Europe for the purpose of making pendulum experiments at the chief initial stations for operations of this sort, in order to bring the determinations of the force of gravity in America into connection with those of other pends of the world; and also for the purpose of making a careful study of the methods of pursuing these researches in the different countries of Europe.

Assistant Peirce sailed from New York on the 3rd of April, 1875. He proceeded at once to England, where he ascertained that the Kew observatory is regarded as the initial point for British pendulum work. This observatory, which is situated in the old deer park at Richmond, is the property of the Crown; but the operations conducted there, which are chiefly of a magnetical and meteorological  description, have been kept up by the Royal Society, through a special committee, and also by the Royal Meteorological Office. R. H. Scott Esq. who directs the Meteorological bureau is also chairman of the Kew committee. The pendulums of the Great Survey of India were swung at this observatory, both before and


after the operations in India, the observatory being occupied at first by Captain Bassevi during a year for this purpose, and afterwards by Captain Heavyside during a year and a half. It is believed that the pendulums of Major General Sir Edward Sabine were also oscillated there; in any case, all the historical English pendulums are there collected and can be swung at any time if necessary.

By the action of the American Minister General Schenk, an application was made, through the British Foreign Office, for permission to experiment with the American apparatus at the Kew Observatory; and to this request a favorable response was eventually received. Late in May 1875 Assistant Peirce proceeded to Germany where a Bessel's convertible pendulum, having the length of one metre between the knife-edges and being a copy of the instrument used in the Prussian survey had already been ordered of the Messrs. Repsold. It may be mentioned that the convertible pendulum, which was invented by Bohnenberger, had been first seriously employed by Kater Bessel, however, described such an improvement as to effect the complete elimination of all effect of atmospheric resistance and friction. Long after Bessel's death, this improved instrument was constructed by Repsold, and was adopted by the Swiss survey and first used by Professor Plantamour, who developed the method of employing it. It is now exclu-


sively used on the continent of Europe, and has received the unanimous sanction of the International Geodetical Association. An instrument of this sort had been ordered by the Coast Survey at the commencement of the pendulum operations in 1872, but owing to the Messrs. Repsold being then occupied with preparations for the transit of Venus, the apparatus was not completed until the spring of 1875. This is not the place for any description of the instrument which was executed with the consummate precision for which this celebrated firm of mechanisms is distinguished. This instrument having been proved, Assistant Peirce readily obtained from Professor Förster, the eminent director of the Berlin observatory and president of the Imperial German Commission of Weights and Measures, the permission to make all necessary experiments in the building of the Office of Weights and Measures in Berlin, upon the very spot where the determination of Bessel had been made. This building has been erected expressly for the purpose of making accurate comparisons of standards of length. It is built with very thick walls of hollow brick, and the comparison chambers are [il.] with some systems of flues, through which, by means of an engine


in an adjoining building, hot air can be conveyed from a furnace or cold air from an ice-house. This building which will serve as a model for similar buildings in other countries (as it already has in France) is the most suitable possible place for pendulum experiments. The building, however, was not sufficiently completed in the summer of 1875 to allow of pendulum experiments being made there to the greatest advantage. It was thought desirable to make a careful comparison of the American reversible pendulum with that of Prussia. The celebrated geodesist Lieutenant-General Dr. Baeyer, the director of Royal Prussian Survey, who furthered  Assistant Peirce's operations in the most gratifying manner throughout his stay upon the continent, at once placed the Prussian instrument at his disposal, and the metre scale of this apparatus, which had already been carefully compared with the Prussian Normal Metre at different temperatures, by Professor Förster, was submitted to fifty independent series of comparisons with the similar scale of the American standard by Assistant Peirce. These operations which yielded a very satisfactory result lasted until July 7th. Assistant Peirce afterwards proceeded to Geneva, where, upon the return of Professor Plantamour


(who was at first absent) arrangements were readily made for oscillating the reversible pendulum at the observatory of the city. Assistant Peirce had then at the outset of his operations with Bessel's pendulum, the signal advantage of receiving the counsels of the distinguished savant who first introduced the use of it and who has studied so carefully the methods of its manipulation. Actual experiments were made upon 17 days, between August 26 and September 17. The method of making the experiments adopted by Assistant Peirce may here be described. It has been slightly modified from time to time, but its latest form is as follows. On the first day, the rigidity of the stand and the position of the centre of gravity of the pendulum are measured. The next day is devoted to comparisons of the pendulum and standard. The oscillations are then commenced; and no measures of the pendulum are made upon days devoted to these experiments. During the swinging of the pendulum the Repsold's "firma" is always forward. Each day the pendulum is first swung with the heavy end up, then with the heavy end down, and after with the heavy end up again. Two such sets of experiments are sometimes made in one day, but this is considered rather objectionable. After four such sets, the pendulum is remeasured the next day. The day is then devoted to remeasuring the flexure of the stand, to interchanging the knife edges, and to determining the centre of gra-


vity before and after this change. In interchanging the knife edges they are never reversed end for end. A day is given to measuring the pendulum. Four more sets of swingings are then made. The pendulum is then again measured as before, and then the determinations of centre of gravity and flexure are repeated. Fifteen days might be occupied by such a determination, but in practice it is necessary to vary the proceeding, more or less. The times of oscillation are determined by observing transits of the pendulum across the web of a telescope and registering the time upon a chronograph. One hundred transits are observed each time, and in one of the following orders:

A. 25 transits from right to left; then 50 from left to right; then 25 from r. to l.

B. 50 transits from l. to r.; then 50 from r. to left.

C. 50 transits from right to left; then, 50 from left to right.

D. 25 transits from left to right; then 50 from right to left; then 25 from left to right.

Choice is made between these methods so that the signals will not interfere with the two second breaks of the chronometer, which affect the same pen. Four sets of transits are so taken that at their mean times respectively the oscillations of the pendulum have the amplitudes 2º, 1 1/2º, 1º, and ½º. Different eyepieces are used with magnifying powers nearly inversely proportional to the amplitudes so that the apparent velocity shall remain constant.

The observatory of Geneva is a small building with one main


room, opening by large glass doors to the north and south. The floor is of asphalte and the instrument rested upon the floor. There was necessarily more or less walking about, and several visitors each day entered at the glass doors just mentioned. Assistant Peirce received every possible assistance and attention from Professor Plantamour and his assistants; but it is necessary to note the fact that the place was hardly suitable for such operations. Observations of time were made by the assistants of the observatory.

At Geneva, Assistant Peirce set up a micrometer in front of the pendulum stand and by means of a weight passing over a pulley whose friction was determined he measured the flexure of the support of the pendulum, and determined the important correction, mounting to over 0.2 mm, to be applied to the length of the seconds pendulum on account of the swinging of the stand from side to side as the pendulum swings.

Proceeding to Paris, Assistant Peirce had the honor and advantage of attending the sittings of the International Geodetical Association and of its standing committee, which met in September, 1875, at the palace of the Ministry of Foreign Affairs. The whole sub-


ject of the pendulum received a thorough discussion, and a resolution was unanimously passed, expressing the sympathy & interest of the association in the expedition of Assistant Peirce.

The reversible pendulum had unfortunately sustained grievous damages in transportation from Paris to Geneva. Thus, one of the great advantages of this instrument received illustration. For if it had been an invariable pendulum, the connection between previous and subsequent operations would have been entirely destroyed; whereas, with the existing construction, the pendulum had only to be put again into condition in order to give results perfectly comparable with those which had gone before. During the interval created by this accident the Geneva observations were completely reduced.

Permission was granted by his excellency M. Wallon, Minister of Public Instruction, Worship, and the Fine Arts, for oscillating the American pendulum at the Observatory at Paris. M. Leverrier afforded every assistance; and the operations were conducted in the great Salle du Méridien, where the pendulums of Borda, of Sabine, and others had previously been swung. The experiments were conducted in the recess at the


northern end of this hall; and were made upon 18 days, between January 18th and February 29th, 1876. The standard clock of the observatory was made use of, and its corrections were furnished by the Observatory. M. Wolf, the well-known astronomer attached to the observatory, to whom the arrangements for the experiments were instructed by the illustrious director, rendered Assistant Peirce in the most gracious manner all the aid that this magnificent institution could furnish.

On the conclusion of the experiments in Paris, Assistant Peirce again repaired to Berlin, and as soon as the great comparing chamber of the bureau of Weights and Measures was ready, experiments were commenced there upon a pier at the western end. As before, every possible assistance was received from Professor Förster and Lieutenant-General Baeyer. The experiments were made upon 24 days from April 19 to June 6, 1876. A clock was furnished by the observatory which was compared with the normal clock whose corrections were furnished by the observatory.

A standard metre with lines, and also cylinders for comparison with an end measure, was at a subsequent visit furnished to


Assistant Peirce by the Imperial Commision of Weights and Measures.

At Berlin, Assistant Peirce invented a new method of recording the mean times of sets of observations of all kinds; and made some steps towards the application of it to the automatic registry of pendulum oscillations. An instrument for this purpose has since been constructed, and will be found described in the Appendix.

After the experiments in Berlin, favorable response having been received to the application of Assistant Peirce for permission to make his experiments at the Kew observatory, he went to England, and commenced experiments without delay. The observations commenced on June and were made on days ending July. The time was observed by Mr. Henry Farquhar, with the transit of the observatory, and four chronometers were kept running at once.

Mr. Peirce Arrived at Boston August 26, 1876. He is at present occupied in completing the connection of the determination of gravity in Europe and America.

Transcription by Sara Barrena (2017)
Una de las ventajas de los textos en formato electrónico respecto de los textos impresos es que pueden corregirse con gran facilidad mediante la colaboración activa de los lectores que adviertan erratas, errores o simplemente mejores transcripciones. En este sentido agradeceríamos que se enviaran todas las sugerencias y correcciones a
Proyecto de investigación "La correspondencia del tercer viaje europeo de Charles S. Peirce (septiembre-noviembre 1877)"

Fecha del documento: 15 de febrero 2017
Última actualización: 17 de agosto 2017

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