Mr. Mann then offered the following resolution, which was adopted: Resolved, That the resolution in relation to the resignation of the Hon. John B. Henderson as a Regent of the Smithsonian Institution be engrossed and transmitted to him. The chancellor stated that the secretary would communicate to Congress the announcement of Senator Henderson's resignation. Executive committee vacancy filled.—The matter of the vacancy in the membership of the executive committee was brought up, and Senator Bacon was nominated for the position. After discussion, the following resolution was adopted: Resolved, That the vacancy in the membership of the executive committee, caused by the resignation of the Hon. John B. Henderson, be filled by the election of the Hon. A. O. Bacon. Models of patents.—Mr. Mann said that there were pending in Congress bills providing for the destruction of the old models that had been on deposit in the Patent Office for many years, and asked if the Smithsonian Institution could make any use of them. The secretary explained that this matter had been brought to the Institution's attention two or three years since, and that about 12,000 of the models had been selected for the use of the industrial exhibit in the Museum. Those left were not suited to museum purposes. Adjournment.-There being no further business to be transacted, on motion the board adjourned. ADVERTISEMENT. The object of the GENERAL APPENDIX to the Annual Report of the Smithsonian Institution is to furnish brief accounts of scientific discovery in particular directions; reports of investigations made by collaborators of the Institution; and memoirs of a general character or on special topics that are of interest or value to the numerous correspondents of the Institution. It has been a prominent object of the Board of Regents of the Smithsonian Institution, from a very early date, to enrich the annual report required of them by law with memoirs illustrating the more remarkable and important developments in physical and biological discovery, as well as showing the general character of the operations of the Institution; and this purpose has, during the greater part of its history, been carried out largely by the publication of such papers as would possess an interest to all attracted by scientific progress. In 1880 the secretary, induced in part by the discontinuance of an annual summary of progress which for 30 years previous had been issued by well-known private publishing firms, had prepared by competent collaborators a series of abstracts, showing concisely the prominent features of recent scientific progress in astronomy, geology, meteorology, physics, chemistry, mineralogy, botany, zoology, and anthropology. This latter plan was continued, though not altogether satisfactorily, down to and including the year 1888. In the report for 1889 a return was made to the earlier method of presenting a miscellaneous selection of papers (some of them original) embracing a considerable range of scientific investigation and discussion. This method has been continued in the present report for 1911. 110 THE GYROSTATIC COMPASS.1 [With 3 plates.] By H. MARCHAND. The gyrostatic compass may be looked upon as one of the most interesting inventions made during recent years. The gyroscope is familiar to all. Nor are we ignorant to-day of the fundamental laws which govern it. The great physicist Foucault first completely formulated them as the result of his profound researches on the subject. The first of these laws is that a gyroscope with perfect freedom of movement—that is, the power to move in any direction, and free from the action of gravity-will tend to maintain the initial position given to it. The second law is that if a gyroscope has only two degrees of freedom, in such a way that it can undergo displacement in two planes only, it must, if subject to the action of gravity, and provided that it is not at the poles of the earth, tend to place itself so that its axis is parallel to that of the earth and accordingly will indicate the direction of true north. A system of this kind is free from the errors which affect the magnetic compass, and therefore the idea of taking advantage of it for navigation must have early attracted the attention of investigators, especially as the general use of steel in the construction of vessels entails grave difficulties in the use of magnetic instruments. Formerly the means at hand were insufficient for constructing a satisfactory, practical instrument, and so, during the time of Foucault, and even much later, the numerous scientists who approached the problem did not meet with much success. A German investigator, Dr. Anschütz, has recently succeeded in constructing an instrument on gyrostatic principles which is practical. In 1900 he commenced the study of a gyroscope with perfect freedom of movement. Later, however, in 1906, he abandoned that for one having only two degrees of freedom. Even with the latter conditions the problem required great nicety. A grave difficulty comes from the fact that such a device is affected, under ordinary circumstances, not only by the rotation of the earth but also by all the forces to which it is subjected because of the rolling 1 Translated by permission from Cosmos, Paris, New Series No. 1385, Aug. 12, 1911, pp. 181-184. of the ship. Therefore, in order to get a good result, it was necessary for the compass to have a very great gyrostatic resistance, so termed, opposing energetically any force tending to change the direction of its axis of rotation, and that the friction of its bearings should be made as small as possible. A consequence of the latter condition, however, would be that the gyrostat would come to its normal position only after a relatively long time, oscillating to and fro about that normal position. Meanwhile it would be subject to new perturbations. Accordingly one great desideratum was to provide some device for lessening these oscillations; at first, Anschütz tried for this purpose a second gyrostat; later he developed a much more simple and efficient method. His gyrostatic compass was tried on the steamer Deutschland in 1908 and has since been used in the German Navy. It has just been adopted by the English Navy, and other navies are also trying it. Let us consider its principles: We know that a gyroscope once started tends to maintain its axis in an invariable direction, and that if any force is applied tending to change this direction, precessional movement takes place, which displaces the axis perpendicular to the direction of the disturbing force. Such being the case, let us imagine a gyroscope, inclosed in an appropriate box, suspended from a float which rests in a liquid bath in such a manner that the gyroscope is perfectly free to swing in any direction like a pendulum which is at rest; the center of gravity of the system is below the metacenter; the gyroscope is mounted at the lowest point possible. Because of its weight the axis of the gyroscope tends to maintain itself, as well as the whole attached mechanism, in a horizontal position. Let us set the gyroscope disk rotating. In the past such rotation could be effected only by rough and very unsatisfactory means; now we have a much more advantageous method at our disposal. We may, for instance, drive it by a little three-phase motor fed by means of fine conducting wires so that the rotation may be kept up indefinitely. As soon as the gyroscope disk is in rapid rotation with its axis horizontal, then if this axis is not in the plane of the terrestrial meridian, the rotation of the earth will tend to alter the axis from its original position. The gyroscope tends to respond, but, restricted by its weight, which forces the axis to remain horizontal, it will undergo only a horizontal displacement. This leads it to take a north and south direction, because as long as its axis is not parallel to that of the earth, the cause of this movement is still effective, so that if it is sufficiently free to move, it will indicate true north. Plate 1 shows a model designed to show experimentally this action. It consists of a small gyroscope, driven by a small three-phase elec |