Chapter 27

5. If the Earth consisted of a thin solid shell upon a liquid interior there would be tides in the liquid interior, the crust would yield to these tides almost as if it were composed of rubber, and the ocean tides would be only an insignificant amount larger than the land tides. As a result we should not see the ocean tides; their visibility depends upon the contrast between the ocean tides and the land tides. If the Earth were absolutely unyielding from surface to center the ocean tides would be relatively 50 per cent. higher than we now see them. The conclusion from these facts is that the Earth yields to the tidal forces a little less than if it were a solid ball of steel, supposing that the well-known rigidity and density existed from surface to center of the ball. This result is established by Darwin's and Schweydar's studies of ocean tides, by studies of the tides in the Earth's surface strata made by Hecker, Paschwitz and others, and by Michelson's recent extremely accurate comparison of land and water tides. Michelson's results establish further that the Earth is highly elastic: though distortion is resisted, there is yielding, but the original form is recovered quickly, almost as quickly as a perfectly elastic body would recover.

6. Some 25 years ago it was discovered by Kustner that the latitudes of points on the Earth's surface are changing slowly. Chandler proved that these variations pass through their principal cycle in a period of 427 days. The entire Earth oscillates slightly in this period. The earlier researches of Euler had shown that the Earth would have a natural oscillation period of 305 days provided it were an absolutely rigid body. Newcomb showed that the period of oscillation would be 441 days if the Earth had the rigidity of steel. As the observed oscillation requires 427 days, Newcomb concluded that the Earth is slightly more rigid than steel.

7. The first waves from a very distant earthquake come to us directly through the Earth. The observed speeds of transmission are the greater, in general, the more nearly the earthquake origin is exactly on the opposite side of the Earth from the observer; that is, the speeds of transmission are greater the nearer the center of the Earth the waves pass. Now, we know that the speeds are functions of the rigidity and density of the materials traversed. The observed speeds require for their explanation, so far as we can now see, that the rigidity of the Earth's central volume be much greater than that of steel, and the rigidity of the Earth's outer strata considerably less than that of steel. Wiechert has shown that a core of radius 4,900 km. whose rigidity is somewhat greater than that of steel and whose average density is 8.3, overlaid by an outer stony shell of thickness 1,500 km. and average density 3.2, would satisfy the observed facts as to the average density of the Earth, as to the speeds of earthquake waves, as to the flattening of the Earth,--assuming the concentric strata to be homogeneous in themselves,--and as to the relative strengths of gravity at the Poles and at the Equator. The dividing line, 1,500 km. below the surface--1,600 km. would be just one fourth of the way from the surface to the center--places a little over half the volume in the outer shell and a little less than half in the core. Wiechert did not mean that there must be a sudden change of density at the depth of 1,500 km., with uniform density 8.3 below that surface and uniform density 3.2 above that surface. The change of density is probably fairly continuous. It was necessary in such a preliminary investigation to simplify the assumptions. The observational data are not yet sufficiently accurate to let us say what the law of increase in density and rigidity is as we pass from the surface to the center.

8. The phenomena of terrestrial magnetism indicate that the distribution of magnetic materials in the Earth is far from uniform or symmetrical; the magnetic poles are distant from the Earth's poles of rotation; the magnetic poles are not opposite each other; the lines of equal intensity as to all the magnetic components involved run very irregularly over the Earth's surface. There is reason to believe that iron in the deep interior of the Earth, in view of its high temperature, is devoid of magnetic properties, but we must not state this as a fact. We know that iron is very widely, but very irregularly spread throughout the Earth's outer strata. Whatever may be the main factors in making the Earth a great magnet, to whatever extent the rotation factor may be important, the Earth's magnetic properties point strongly to a very irregular distribution of magnetic materials in the outer strata where the temperatures are below that at which magnetic materials commonly lose their polarity.

9. Irregularities in the direction of the plumb-line and in the force of gravity as observed widely and accurately over the Earth's surface indicate that the surface strata are very irregular as to density. To harmonize the observed facts Hayford has shown the need of assuming that the heterogeneous conditions extend down to a depth of 122 km. from the surface. Below that level the Earth's concentric strata seem to be of approximately uniform densities.

10. The radio active elements have been found by Strutt and others in practically all kinds of rock accessible to the geologists, but they are not found in significant quantities in the so-called metals which exist in a pure state. These radioactive elements are liberating heat. Strutt has shown that if they existed down to the Earth's center in the same proportion that he finds in the surface strata they would liberate a great deal more heat than the body of the Earth is now radiating to outer space. The conclusion is that they are restricted to the strata relatively near the Earth's surface, and are not in combination with the materials composing the Earth's core. They have apparently found some way of coming to the higher levels. Chamberlin suggests that as they liberate heat they would raise surrounding materials to temperatures above the normals for their strata, and that these expanded materials would embrace every opportunity to approach the surface of the Earth, carrying the radioactive substances with them.

The evidence is exceedingly strong, and perhaps irresistible, to the effect that the Earth is now solid, or acts like a solid, from surface to center, with possibly local, but on the whole negligible, pockets of molten matter here and there; and further, that the Earth existed in a molten, or at the least a thickly plastic, state throughout a long part of its life. The nucleus, whether gaseous or meteoric, from which I believe it has grown, may have been fairly hot or quite cold, and the materials which were successively drawn into the nucleus may have been hot or cold: heat would be generated by the impacts of the incoming materials; and as the attraction toward the center of the mass became strong, additional heat would be generated in the contraction process. The denser materials have been able, on the whole, to gravitate to the center of the structure, and the lighter elements have been able, on the whole, to rise to and float upon the surface very much as the lighter impurities in an iron furnace find their way to the surface and form the slag upon the molten metal. The lighter materials which in general form the surface strata are solid under the conditions of solids known to us in every-day life. The interior is solid or at least acts as a solid, because the materials, though at high temperatures, are under stupendous pressures. If the pressures were removed the deep-lying materials would quickly liquefy, and probably even vaporize.

If the Earth grew from a small nucleus to its present size by the extremely gradual drawing-in of innumerable small masses in its neighborhood, the process would always be slow; much slower at first when the small nucleus had low gravitating powers, more rapid when the body was of good size and the store of materials to draw upon plentiful,and gradually slower and slower as the supply of building materials was depleted. Meteoric matter still falls upon and builds up the Earth, but at so slow a rate as to increase the Earth's diameter an inch only after the passage of hundreds of millions of years. If the Earth grew in this manner, the growth may now be said to be essentially complete, through the substantial exhaustion of the supply of materials.

Whether the Earth of its present size was ever completely liquefied, that is, from center to surface, at one and the same time, is doubtful. The lack of homogeneity, as indicated by the plumb-line, gravity, terrestrial magnetism and radiaoctive matter, extending in a perceptible degree down to 122 km., and quite probably in lesser and imperceptible degree to a much greater depth, is opposed to the idea.

Solidification would respond to the fall of temperature down to the point required under the existing high pressures, and it is probable that the solidification began at the center and proceeded outwards. It is natural that the plastic state should have developed and existed especially during the age of most rapid growth, for this would be the age of most rapid generation of heat. Later, while the rate of growth was declining, the body could probably have solidified slowly and successively from center out to surface. In later slow depositions of materials, the denser substance would not be able to sink down to the deepest strata: they must lie within a limited depth and horizontal distance from where they fell, and the outer stratum of the Earth would be heterogeneous in density.

The simplest hypothesis we can make concerning the Earth's deep interior is that the chief ingredient is iron; perhaps a full half of the volume is iron. The normal density of iron is 7.8, and of rock formations about 2.8. If these are mixed, half and half, the average density is 5.3. Pressures in the Earth should increase the density and the heat in the Earth should decrease the density. The known density of the Earth is 5.5. We know that iron is plentiful in the Earth's crust, and that iron is still falling upon the Earth in the form of meteorites. The composition of the Earth as a whole, on this assumption, is very similar to the composition of the meteorites in general. They include many of the metals, but especially iron, and they include a large proportion of stony matter. Iron is plentiful in the Sun and throughout the stellar universe. Why should it not be equally plentiful in the materials which have coalesced to form the Earth? It is difficult to explain the Earth's constitution on any other hypothesis.

The Earth's form is that which its rotation period demands. Undoubtedly if the period has changed, the form has changed. Given a little time, solids under great pressure flow quite readily into new forms. Now any great slowing-down of the Earth's rotation period within geological times would be expected to show in the surface features. The strata should have wrinkled, so to speak, in the equatorial regions and stretched in the polar regions, if the Earth changed from a spheroid that was considerably flatter than it now is, to its present form. Mountains, as evidence of the folding of the rock strata, should exist in profusion in the torrid zone, and be scarce in or absent from the higher latitudes of the Earth. Such differential effects do not exist, and it seems to follow that changes in the Earth's rotation period and in its form could have been only slight while the stratification of our rocks was in progress.

Geologists estimate from the deposition of salt in the oceans, and from the rates of denudation and sedimentation, that the formation of the rock strata has consumed from 60,000,000 to 100,000,000 years. If the Earth had substantially its present form 80,000,000 years ago we are safe in saying that the period of time represented in the building up of the Earth from a small nucleus to its present dimensions has been vastly longer, probably reckoned in the thousands of millions of years.

For more than a century past the problem of the evolution of the stars, including the solar system and the Earth, has occupied the central place in astronomical thought. No one is bold enough to say that the problem has been solved. The chief difficulty proceeds from the fact that we have only one Earth, one solar system and one stellar system available for tests of the hypotheses proposed; we should like to test them on many systems, but this privilege is denied us. However, the search for the truth will undoubtedly proceed at an ever increasing pace, partly because of man's desire to know the truth, but chiefly, as Lessing suggested, because the investigator finds an irresistible satisfaction in the process. There is always with him the certainty that the truth is going to be incomparably stranger and more interesting than fiction.

A METRICAL TRAGEDY

BY DR. JOS. V. COLLINS

STEVENS POINT, WIS.

THE war in Europe has opened up a large field of trade in South America. Three things especially stand in the way of its development, viz., the absence of a proper credit system, the failure to make goods of the kind demanded and third, the use of our antiquated system of weights and measures, all the South American countries employing the metric system. Of these three obstructing influences, the first two are in a fair way to be obviated soon; not so the last.

It is the use by our modern progressive country of an ancient system of weights and measures which it is here proposed to discuss and show up as an absurdity. Our present system is organized and set forth in arithmetics under some fifteen so-called "tables." These tables are all different and there is no uniformity in any one table. Only one unit suggests convenience in reductions, viz., hundredweight. It is easy to reduce from pounds to hundredweight and vice versa. Some fifty ratio numbers have to be memorized or calculated from other memorized numbers to make the common needed reductions. History shows that ancient Babylonia had tables superior to those now in use, and ancient Britain a decimal scale which was crowded out by our present system.

The metric system of weights and measures was developed in France about 1800 and has come to be employed over all the civilized world except in the United States, Great Britain and Russia. The system was legalized in the United States in 1866 but not made mandatory and here we are fifty years later using the old system, with most of the civilized world looking on us with more or less scorn because of our belatedness.

In this age everywhere the cry is efficiency, always more efficiency. Ten thousand improvements and labor-saving devices are introduced every day. But here is an improvement and labor-saving device which would affect the life of every person in the land and in many instances greatly affect such persons' lives, and yet almost no one really knows anything about the matter.

So let us now consider the good points in the metric system (each implying corresponding elements of great weakness in the common system), and then study briefly what stands in the way of its adoption in this country. These good points are:

First, the metric units have uniform self-defining names (cent, mill, meter and five more out of the eleven terms used already familiar to us in English words), are always the same in all lands, known everywhere, and fixed with scientific accuracy.

Second, every REDUCTION is made almost instantaneously by merely moving the decimal point. There are no reductions performed by multiplying by 1,728 or 5,280, etc., or dividing by 5 1/2, 30 1/4 or 31 1/2, etc., and hence there is A GREAT SAVING in the labor and time of making necessary calculations.

Third, there are but FIVE tables in the metric system proper, these taking the place of from twelve to fifteen in our system (or lack of it). These are linear, square, cubic, capacity and weight.

Fourth, any one table is about as easy to learn as our United States money table, and after one is learned, it is much easier to learn the others, since the same prefixes with the same meanings are used in all.

Fifth, the weights of all objects are either known directly from their size, or can be very quickly found from their specific gravities.

Sixth, the subject is made so much easier for children in school that a conservative expert estimate of the saving is two thirds of a year in a child's school life. The rule in this country is eight years of arithmetic, the arithmetic occupying about one fourth of the child's activity. With metric arithmetic substituted for ours, what it now takes two years to prepare for, could be easily done in 1 1/3 years. This involves an enormous waste of money and energy every twelvemonth.

Seventh, only ONE set of measures and ONE set of weights are needed to measure and weigh everything, and ONE set of machines to make things for the world's use. There would be no duplication of costly machinery to enter the foreign trade field, thus securing enormous saving. It is well known that the United States and Great Britain have lost a vast amount of foreign commerce in competition with Germany and France, because of their non-use of the metric units. Britain realizes this and is greatly concerned over the situation.

Eighth, every ordinary practical problem can be solved conveniently on an adding machine. Our adding machines are used almost solely for United States money problems.

Ninth, no valuable time is lost in making reductions from common to metric units, or vice versa, either by ourselves or foreigners. To make our sizes in manufactured goods concrete to them foreign customers have to reduce our measures to theirs and this is a weariness to the flesh.

Tenth, the metric system is wonderfully simple. All the tables with a rule to make all possible reductions can be put on a postal card.[1]

[1] See article by the writer in Education (Boston), Dec., 1894.

The metric weights and measures constitute a SCIENTIFIC SYSTEM; our weights and measures are a DISORGANIZATION. Naturally one can expect a GREAT SAVING OF TIME, THOUGHT AND LABOR from the use of a system, and this is the fact. If one dared introduce ordinary arithmetical problems into an article like this, it would be easy to show by examples how a person has to be something of a master of common fractions in order to solve in our system common every-day problems, whereas in the metric system nearly everything is done very simply with decimals. In our system a mechanic after making a complicated calculation with common fractions is as likely as not to get his result in sixths, or ninths, etc., of an inch, whereas his rule reads to eighths, or sixteenths, and he must reduce his sixths, or ninths, to eighths, or sixteenths, before he can measure off his result. In the metric system results always come out in units of the scale used. The metric system measures to millimeters or to a unit a trifle larger than a thirty-second of an inch. In our system one is likely to avoid sixteenths or thirty-seconds on account of the labor of calculation. Then, besides, the amount of figuring is so much less in the metric system. Take the case of a certain problem to find the cubical contents of a box. Our solution calls for 80 figures and the metric for 35, and this is a typical case, not one specially selected. Thus, metric calculations, while only from one third to two thirds as long, are likely to be two or three times as accurate, are far easier to understand, and the results can be immediately measured off. Hence, we waste time in these four ways. Shakespeare in Hamlet says: "Thus conscience does make cowards of us all." In like vein it might be said: Thus custom (in weights and measures) doth make April fools of us all. It is no exaggeration to say that counting grown-ups solving actual problems and children solving problems in school we are sent on much more than a billion such April fool errands round Robin Hood's barn every year.

Noting how much time is saved in making simple every-day calculations by using the metric system, suppose that we assume of the 60 or more millions of adults in active life in this country, on the average only one in 60 makes such calculations daily and that only twenty minutes' time is saved each day. Let us suppose that the value of the time of the users is put at $2.40 per day or 10 cents for 20 minutes. Then 1,000,000 users would save $100,000 per day or $30,000,000 per year. But perhaps some one is saying that much of this time is not really saved, since many persons are paid for their time and can just as well do this work as not. The answer to this is that in many instances such calculations take the time of OTHERS as well as the person making the calculation. Occasionally a contractor might hold back, or work to a disadvantage a gang of a score of workmen while trying to solve a problem that came up unexpectedly.

An estimate of the value of all weighing and measuring instruments places the sum at $150,000,000. Thus, we see that in five years, merely by a saving in TIME--for time is money--all metric measuring and weighing instruments could be got NEW at no extra expense. This estimate of the cost of replacing our weighing and measuring instruments by new metric ones and of saving time has been made by others with a similar result.

A matter of very much more importance than that just discussed is the extra unnecessary expense put upon education, viz., two thirds of a year for every child in the land. Presumably if the metric system were in use with us, all our children would stay in school as long as they now do, thus getting two thirds of a year farther along in the course of study. Actually, if arithmetic were made more simple, vast numbers would; stay longer, since they would not be driven out of school by the terrible inroads on their interest in school work by dull and to them impossible arithmetic. If metric arithmetic texts were substituted for our present texts, it is safe to say children would average one full year more of education. What the increased earning power would be from this it would be hard to estimate, but clearly it would be a huge sum.

Consider also how much more life would be worth living for children, teachers and parents if a very large portion of arithmetical puzzles inserted to qualify the children to understand our crazy weights and measures were cut out of our text-books. If we were to adopt the metric system, literally millions of parents would be spared worry, and shame, and fear lest Johnny fail and drop out of school, or Mary show unexpected weakness and have to take a grade over again; uncounted thousands of teachers would be saved much gnashing of teeth and uttering of mild feminine imprecations under their breath; and, best of all, the children themselves would be saved from pencil-biting, tears, worries, heartburns, arrested development, shame and loss of education!

A committee of the National Educational Association has recently reported that Germany and France are each two full years ahead of us in educational achievement, that is, children in those countries of a certain age have as good an education as our children which are two years the foreign childrens' seniors. Surely one of these years is fully accounted for by the inferiority of our American ARITHMETIC and SPELLING. This much, at least, of the difference is neither in the children themselves, nor in the lack of preparation of our teachers, nor in educational methods.