ON A PHYSICAL OBSERVATORY. BY PROF. JOSEPH HENRY. SMITHSONIAN INSTITUTION, MY DEAR SIR: Yours of the 28th of November was duly received, but I delayed answering it until the pressure of business which accumulated during my absence should have somewhat subsided, and, also, that I might receive the plans which you mention. I am now gratified in being able to inform you that my visit to Europe was both pleasant and profitable, and that I have returned much improved in health and with enlarged views as to the present state of science in the Old World. While abroad I gave special attention to physical observatories, or which there are several in England and on the continent, although there is no one which fully realizes my idea of what such an establishment ought to be. A physical observatory is one the primary object of which is to investigate the physical phenomena of the earth and the heavenly bodies in contradistinction to an ordinary astronomical observatory, which is principally devoted to the observation and discussion of the motions of the planets, and the determination of the relative positions of the fixed stars. Of the latter kind but one or two are needed in any country, and as these require a numerous corps of observers and computers they can only be supported by appropriations annually from a national government. The United States Observatory at Washington is of this character, and, including all expenses, requires an annual appropriation of at least $50,000. The labors of such an observatory are indispens able to the advancement of the science of theoretical astronomy, and its application to geodesy and geography. The establishment I would advise you to found is of the character of the one first mentioned, namely, a physical observatory, the principal object of which would be, as I have indicated, to investigate the nature and changes of the constitution of the heavenly bodies; to study the various emanations from these in comparison with the results of experi ments, and to record and investigate the different phenomena which are included under the general term of terrestrial physics. A wide field has been opened for the study of the nature of the sun and other heavenly bodies by the application of the spectroscope, different modifications of the telescope, and other lately invented appliances. We now know that the sun is undergoing remarkable changes, the character of which can only be ascertained by the results of accurate observations compared with those of experimental investigation. The observer should divide his attention between the phenomena revealed by a critical and continued examination of the sun and the production of similar phenomena in the laboratory. In this way European investigators have arrived at most interesting results. Again, we know that the emanations from the sun, and probably from the stars, differ essentially in character. There is, first, the ema nation known as light, which of itself consists of various rays, which generally indicate the incandescence of substances, which give the sensation of different colors, and those which, in their ordinary condition, are imperceptible to the eye, but which may be perceived by that organ after they have passed through certain liquids; next, the heat emanation, which is also of different kinds; then the chemical emanation, by which photographic impressions are produced; and, lastly, the phosphorogenic emanation, which abounds also in the electric discharge, and which produces the glow of the diamond and the luminosity of the compounds of lime, barium, and other substances with sulphur. To study these or other emanations as they may appear in the fixed stars, or are reflected from the moon and planets, or as they may be found in the aurora borealis, the zodiacal light, and in shooting-stars or larger mete ors, requires peculiar instruments, and such as are not found, at present, in ordinary astronomical observatories. For example, the celestial phe nomena which address themselves to the sense of sight are studied by means of refracting telescopes, as are, also, those of the photographic ray, although this requires a peculiar form of lens, while the heat-ray of lower intensity and the phosphorogenic ray are not transmitted by glass; the former is readily converged to a focus by a lens of rock-salt, and the latter by one of quartz. They may all, however, as in the case of light, be concentrated into foci by metallic reflectors. In regard to terrestrial physics, the phenomena are also various, and the forces by which they are produced are constantly changing both in intensity and, in some cases, in direction. We now know that the magnetism of the earth scarcely remains the same from one moment to another, and that these changes are connected with the appearance of the aurora borealis and electrical discharges in the atmosphere. They, also, in all probability, may ultimately be referred to disturbances produced by external influences, such as those from the sun, moon, and planets. Furthermore, we may now consider the whole earth as an immense conductor charged with negative electricity, of which the intensity is in a continued state of change, and of which a knowledge of the laws, as well as those of the changes of magnetism, is highly desirable. For the proper study of these, continuous self-recording instruments are necessary. There is also an important field of observation in regard to ordinary meteorology, such as the changes of the pressure of the atmosphere, and its connection with other phenomena; of the normal and abnormal winds; isolated currents of the atmosphere, and especially those of a vertical direction; the radiation of heat from clouds and different terrestrial surfaces; the variation of its intensity in ascending above and penetrating below the surface of the earth, &c. In short, the field is almost boundless, and every year reveals new facts in terrestrial and celestial physics, which never fail to furnish new points for investigation to those who are qualified by education and endowed by nature for their proper appreciation. The conductor of an observatory, such as I have mentioned, to be successful, must have peculiar characteristics. He must possess a minute knowledge of all the latest discoveries in physics, a keen eye to detect new appearances, imagination to suggest hypothetical causes, logical power to deduce consequences from these to be tested by observation or experiment, and ingenuity to devise apparatus for verifying or disproving his deductions. When such a man is found he should be consecrated to science and fully furnished with all the implements necessary for the prosecution of his researches, those of physics as well as of astronomy, and himself and family placed beyond all anxiety as to the supply of their necessary wants. It may not be amiss to combine with his studies and duties, in the way of research, a small amount of lecturing just enough by sympathetic communication with admiring pupils to fan, as it were, his enthusiasm, and to impart a portion of it to others. He should also have at his command a skillful workman, who, under his direction, could construct the temporary apparatus which are constantly required in original research. It is also important that he be associated with the faculty of a well-endowed college or university, to which he will become an important acquisition both in regard to the reputation which he will give to the institution, and the effect he will have on the other members of the faculty in the way of stimulating them to higher efforts. In such an association he can call for the coöperation of the professors, and especially that of the physicist, the chemist, and the mathematician. One of the most important points, perhaps, to which I should call your attention is that of the building to be erected, since, from the tendency to error in this line, more injury has resulted to public institutions in this country than from any other cause. It should be recollected that "money is power;" that every dollar possesses a definite amount of potential energy, as it were, which can always command intellectual or physical labor. But money as a power is unlike all other kinds of power, in that it is, by judicious investment, capable of yielding a constant supply of energy, in the way of interest, without diminishing the original amount. It is, therefore, in the highest degree injudicious in the founding of an establishment to exhaust the source of its power by architectural displays not absolutely required, and which may forever involve a continual expense from the remaining funds to keep them in repair. As a general rule, the buildings of educational or scientific institutions should be gradually evolved from the experience and wants of the establishment, and not, as is too frequently the case, from a priori misconceptions of those who have no adequate idea of the uses to which the structure is to be applied. It should be impressed upon the public that buildings do not constitute an institution, and that reputation and usefulness in science do not flow from visible and tangible manifestations, but are the immaterial fruit produced by the spirit of an organization. I trust that millions of human beings yet unborn will be familiar with the intellectual results of your observatory, although a single inquiry may never be made as to the style of the building in which these results have been produced. My advice, then, would be: first, if possible, that the right man be procured for director; secondly, that the principal instruments be constructed under his supervision; and, thirdly, that the operations be commenced in an inexpensive wooden building, which will be found better in many respects for physical and astronomical observations than one of stone and brick. The instruments could be insured, I should think, at a small premium, and in that case, if destroyed by fire, might be replaced by others embracing the improvements which may have been suggested in the mean time. As an illustration of what I have just said in regard to the building, I may mention that in a visit to Mr. Lockyer I found him carrying on a series of observations which have challenged the admiration of the world in a temporary structure made of rough boards, unplastered, and scarcely including a space of fifteen feet square. As to the location of your observatory, you will infer from what I have said that I think it important to connect it with some well-endowed and well-established college or university. JOSEPH HENRY, Secretary Smithsonian Institution. То THE HISTORY OF MY YOUTH: AN AUTOBIOGRAPHY OF FRANCIS ARAGO. [To keep up the series of publications of eulogies of distinguished men, which has been a special feature of the Appendix to the Smithsonian Reports, the following autobiography and the eulogies of Herschel and Fourier are copied from the volume, now out of print, of the translations by the late Admiral Smyth, the late Rev. Baden Powell, and Prof. Grant, from the works of Arago.-J. H] I have not the foolish vanity to imagine that any one, even a short time hence, will have the curiosity to find out how my first education was given, and how my mind was developed; but some biographers, writing off-hand and without authority, having given details on this subject utterly incorrect, and of a nature to imply negligence on the part of my parents, I consider myself bound to put them right. I was born on the 26th of February, 1786, in the commune of Estagel, an ancient province of Roussillon, (department of the Eastern Pyrenees.) My father, a licentiate in law, had some little property in arable land, in vineyards, and in plantations of olive trees, the income from which supported his numerous family. I was thus three years old in 1789, four years old in 1790, five years. in 1791, six years in 1792, and seven years old in 1793, &c. The reader has now himself the means of judging whether, as has been said, and even stated in print, I had a hand in the excesses of our first revolution. My parents sent me to the primary school in Estagel, where I learned the rudiments of reading and writing. I received, besides, in my father's house, some private lessons in vocal music. I was not otherwise either more or less advanced than other children of my age. I enter into these details merely to show how much mistaken are those who have printed that at the age of fourteen or fifteen years I had not yet learned to read. Estagel was a halting place for a portion of the troops who, coming from the interior, either went on to Perpignan, or repaired direct to the army of the Pyrenees. My parents' house was therefore constantly full of officers and soldiers. This, joined to the lively excitement which the Spanish invasion had produced within me, inspired me with such decided military tastes that my family was obliged to have me narrowly watched to prevent my joining by stealth the soldiers who left Estagel. It often happened that they caught me at a league's distance from the village, already on my way with the troops. On one occasion these warlike tastes had nearly cost me dear. It was the night of the battle of Peires-Tortes. The Spanish troops in their retreat had partly mistaken their road. I was in the square of the vil |