摘要:

The first recorded estimate of the density of the Earth was made by Newton. It is to be described rather as a guess than as an estimate, as may be seen by reading Newton's original words (Principia, Book III, Prop. X, Theorem X):“But that our globe of Earth is of greater density than it would be if the whole consisted of water only, I thus make out. If the whole consisted of water only, whatever was of less density than water, because of its less specific gravity, would emerge and float above. And upon this account, if a globe of terrestrial matter, covered on all sides with water, was less dense than water, it would emerge somewhere; and the subsiding water falling back, would be gathered to the opposite side. And such is the condition of our Earth, which in a great measure is covered with seas. The Earth, if it was not for its greater density, would emerge from the seas, and, according to its degree of levity, would be raised more or less above their surface, the water of the seas flowing backwards to the opposite side. By the same argument, the spots of the Sun, which float upon the lucid matter thereof, are lighter than that matter. And however the planets have been formed, while they were yet in fluid masses, all the heavier matter subsided to the center. Since, therefore, the common matter of our Earth on the surface thereof is about twice as heavy as water, and a little lower, in mines, is found about three or four, or even five times more heavy, it is probable that the quantity of the whole matter of the Earth may be five or six times greater than if it consisted all of water; especially since I have before showed that the Earth is about four times more dense than Jupiter

ISSN:0002-8606    

DOI:10.1029/TR007i001p00025

年代:1926

数据来源: WILEY

摘要:

Mr. Adams has asked me to present this subject, not because I have made any important new contributions to it, but because I recently compressed what we know of the interior of the Earth into ten one‐hour lectures, which material was then further abstracted into a one‐hour lecture at another institution. It is only one additional step in high‐pressure technique, with which Mr. Adams is so familiar, to compress the one‐hour lecture into ten minutes.one‐hour lecture into ten minutes. The title says “seismic waves.” I would broaden it to “elastic waves,” for the earthquakes are not essential to this branch of the science of the Earth's interior structure, a science that I have ventured to call geo‐taxology. Earthquakes are only a convenient means, though not a very satisfactory one, for supplying elastic waves. Future progress in the science will undoubtedly see an increasing use of artificial and therefore controllable waves, such as may be produced by an explosion or by the f

ISSN:0002-8606    

DOI:10.1029/TR007i001p00026

年代:1926

数据来源: WILEY

摘要:

The Earth is now believed to have a real crust—not in the old sense of a solid layer floating on a liquid interior, but rather in the sense of a thin covering of material radically different in composition from the sphere which it surrounds. It is interesting to recall that only a few decades ago Osmond Fisher argued with convincing and almost flawless logic that the solid crust of the Earth rested on a mobile liquid. But it is now universally admitted that the whole Earth (except possibly near the center), far from having the mobility commonly associated with the word liquid, has a rigidity approaching or exceeding that of stee

ISSN:0002-8606    

DOI:10.1029/TR007i001p00029

年代:1926

数据来源: WILEY

摘要:

The preceding speakers have pointed out several of the lines along which we arrive at a knowledge of the constitution of the Earth. In these, and several other, ways we have come to believe, and with a high degree of probability of our belief, that a core of metallic iron, or nickel‐iron, occupies the center of the Earth. This metallic core has a radius of about 3,400 kilometers. It changes, by the gradually increasing assumption of silicate material, first into a “lithosporic” shell—one in which silicates (especially olivine and pyroxene) are included sporadically in the metal, and then into a “ferrosporic” shell, in which gradually decreasing amounts of metal occur sporadically in silicate rock. This mixed zone is about 1,400 kilometers thick, and, for purposes of computation, we may assume that the lithosporic and the ferrosporic shells are each 700 kilometers thick. Outside of this is a shell of peridotite—a rock made up of olivine and pyroxene—which is about 1,540 kilometers thick, and above this the “crust” of the Earth, about 60 kilometers thick, the lower two‐thirds being basaltic and the upper one

ISSN:0002-8606    

DOI:10.1029/TR007i001p00030

年代:1926

数据来源: WILEY

摘要:

How the Earth acquired an atmosphere and where the oceans came from, have been fascinating problems ever since there were children to ask questions and grown‐ups who couldn't answer them. However, experiments of the physicist and observations of the geologist and the astronomer have furnished the warp and the woof with which the mathematician at last has woven a theory that clothes both these Sphinxes in rare and beautiful raiment.To begin, not truly at the beginning, but as far back as even part‐knowledge permits, we believe that all that we call electricity and all that we call matter consist of two things as yet unresolved—the electron and the proton, the negative and the positive electric" atoms, or at most, these ultimate charges and their carriers. At any rate, these are the most elementary entities of which there is any fairly definite evidence. We have no knowledge of the origin of either the electron or the proton. They can exist separately, from which we infer that they may have originated differently and in different amounts, the excess diffusing itself to infinite rarity. On the other hand, the equality of their charges suggests a common and simultaneous origin. But, be that as it may, they usually are combined in various equal numbers, thereby forming all the material elements from hydrogen to uranium. Hence, wherever matter occurs in great quantity, as in a star or a planet, one may expect to find all the possible elements in varying proportions, and also such compounds of them as the temperature and other conditions favor. Presumably, therefore, every heavenly object, however nebulous or condensed, has within itself, as certainly as our own sun has, the makings of an atmosphere and an ocean. Evidently, then, when the Earth was pulled out of the sun by the tidal action of a passing star of much greater mass, there were taken along the hydrogen, oxygen, and nitrogen of the ocean and the air as well as the iron, silicon, aluminum, and other elements of the lithos

ISSN:0002-8606    

DOI:10.1029/TR007i001p00032

年代:1926

数据来源: WILEY

摘要:

In 1662 the French settlement along the St. Lawrence River (Fig. 1) was faced with a liquor problem which broke the heart of Bishop Laval, who at that time was head of the Roman Catholic Church in Canada. Excommunication and every means within his power were used to prohibit the sale and use of liquor, but all to no avail, and as a last resource he sailed for old France, hoping to secure assistance from the home government. Hardly had he left the shores of New France when it was believed by many a Mightier Agency had interfered, for, in the year 1663, the St. Lawrence valley was rocked by an earthquake which, if we are to believe history, moved mountains, changed river courses, and, to use the words of the native Indians, “the very trees in the forest danced as though they were intoxicated

ISSN:0002-8606    

DOI:10.1029/TR007i001p00041

年代:1926

数据来源: WILEY

摘要:

The Coast and Geodetic Survey has experienced so much difficulty in the past few years in obtaining satisfactory first‐order theodolites, and by this I mean instruments which can be read to one second of arc, that we have decided to design an instrument ourselves which will embody the various desirable features of existing theodolites, and also such other characteristics as our field experience has indicated will aid in making a more rugged, portable, and easily operated instrument.Briefly, the essentials of a theodolite such as we need are lightness, ruggedness, a perfectly graduated circle, frictionless centers, and perfect optical qualities. Perfection, of course, can only be approximate

ISSN:0002-8606    

DOI:10.1029/TR007i001p00046

年代:1926

数据来源: WILEY

摘要:

The invar base‐line tapes used by the U.S. Coast and Geodetic Survey are tested at the Bureau of Standards. Since these tapes are used in the fundamental geodetic surveys of this country, including international boundary lines, it is essential that every precaution be used in the standardization.It is now possible to measure the change in the distance between the end graduation lines of such a tape when a small weight is placed on the tape, even if the weight is as small as an ordinary wire paper clip. This effect can be calculated mathematically from the weight of the paper clip and there is agreement between the observations and the calculations to about the one fifty‐millionth part of the total length of the t

ISSN:0002-8606    

DOI:10.1029/TR007i001p00049

年代:1926

数据来源: WILEY

摘要:

The general plan of extending the first‐order level net of the United States has been to locate the lines in such a way that eventually no place in the country will be more than fifty miles from a standard bench mark.In prosecution of this plan, 50,000 miles of first‐order levels have been run by the U.S. Coast and Geodetic Survey, the U.S. Geological Survey, the Corps of Engineers, U.S. Army, the U.S. Lake Survey, the Mississippi and Missouri River Commissions, and a number of the leading railroads. The work enters every State of the union but one—Delaware— and forms over one hundred c

ISSN:0002-8606    

DOI:10.1029/TR007i001p00050

年代:1926

数据来源: WILEY

摘要:

At the meeting of the Section of Geodesy held last April, a report was given of the general plan for the readjustment of the first‐order triangulation in the western part of the United States. This plan was conceived by Major Bowie and formulated by him in a general way early in 1924. We shall now give some account of the practical application of this Bowie method to the extensive scheme of triangulation west of the 98th meridian, inclusive of the arc along this meridian.The first step in the general scheme is to adjust a figure at the junction of two arcs, so that a length and azimuth of a line may be determined that is to be held fixed in the adjustment of the section ending with this line. In the ideal junction figure, a measured base should be found and an observed Laplace azimuth. In some cases, where such conditions are found, the junction figure may consist of a couple of quadrilaterals; in other cases, a more extensive figure has to be used, because of the rather involved figures in the triangulatio

ISSN:0002-8606    

DOI:10.1029/TR007i001p00051

年代:1926

数据来源: WILEY