The realm of nature : an outline of physiography

Front matter

22102380124

Med

UNIVERSITY EXTENSION MANUALS

Contents

CHAP.

Definition and scope of Physiography . §§ 1-23, p. 1

Properties of matter and measurement of space §§ 24-48^. 15

Chapter I The Study Of Nature

1. Physiography means literally the description of Nature. In order to describe anything we must know something about it, and in order to know something about anything we must study it. Knowledge obtained by the best method of study is science, and it differs from knowledge otherwise obtained in being so clear and definite that every step leading to the final result may be recalled and tested, if any doubt should arise as to its trustworthiness. Hence description based on science is clear and full, and this is the kind of description required in Physiography.

2. Nature means all creation ; not only all created

things but also all the changes they undergo. The scope of Physiography is thus immense but not unlimited. It includes everything of which we can gain knowledge in the Earth and beyond it, and every change now happening or of which a record has been left, together with the causes of all these changes. It is, however, customary to exclude the First Cause of all from consideration in connection with the account of facts and immediate causes. Theology — the

study of the Creator — is in itself an immense field of science, and although it accounts for the origin of Nature, it may be readily separated from the study of natural facts and phenomena. The chief reason for separating Theology from Physiography is that authorities are greatly divided as to the right means of studying the former science, while every one js agreed as to the right method of studying Nature.

A description of the steam-engine which did not refer to Watt and other inventors and give something of their biography would not be held satisfactory unless some explanation of the omission were given, such as the desire to avoid controversy. For the same reason in a general description of Nature it is necessary to insist on the relation of Nature to God, and explain why this relation is not more fully dealt with.

3. Science is organised and accurate knowledge, and consequently its range has no limits ; it is necessary in order to understand Nature and to define the limits of the known. Science deals with everything, and its first duty is to classify by observing resemblances and differences.

4. Comparison and Description. — Suppose that we were comparing the tastes of different kinds of fruit in a garden. It is not enough to pluck bunches of red currants, black currants, gooseberries, and raspberries off the bushes and eat them. Each bunch must be classified into berries and leaves or stems ; the former are to be tasted, the latter to be thrown away and thought no more of. Without this precaution the taste of gooseberries might be compared with that of black currant leaves, and different tasters would give irreconcilable reports. When we compare the various things around us, a preliminary classification is quite as much required to ensure that we compare things that are comparable. If we were to take into account mountains , pain, rivers, happiness , air , beauty , and motio7i , the description would be very confused and puzzling. When several people who have had the same opportunity of seeing, describe an event, the descriptions are almost sure to differ among themselves. This is because a different impression is produced on each mind, and the various subjective sensations of interest, or fear, or pleasure, or surprise, are confused to a greater or less degree with the objective facts. A scientific description should be as free as possible from all subjective colouring ; a mountain must not be described vaguely as impressive in its grandeur or beautiful in its colouring, but its height and the nature of its rocks and vegetation must be specified. Nature presents us with so many pheno mena to observe, and these are to all rightly constituted minds so full of wonder, beauty, and charm that we are apt to be dazzled and distracted, and even if our attention is roused it is too often satisfied by the first superficial impressions. It is only by putting aside these and looking at bare facts and abstract principles that we can truly understand our natural surroundings and so fully appreciate “all the wonder and wealth ” of the Universe in its deepest meaning.

5. Real Things. — The first classification of things is into (a) Things that exist only in our own minds ; (b) things that exist outside of us and independent of us. Emotions, feelings, tastes, and beliefs belong to the former class and are termed subjective things. Facts and phenomena which exist whether we know of them and understand them or not, are termed objective or real things. The real things of Nature are the objects of physical science, and they alone fall to be considered here. The one test of reality in Nature is essential permanence notwithstanding changes of form. Only those things are real which can neither be created nor put out of existence by human power. Subjective things, such as pain, happiness, beauty, may be readily produced and destroyed, hence however vivid the impression of them may be they are not real, in our sense of the word, and form no part of Physiography.

6. Definition of Physiography. — Physiography is an account of physical science as a whole. It describes the substance, form, arrangement, and changes of all the real things of Nature in their relations to each other, giving prominence to comprehensive principles rather than to isolated facts. This definition of the term Physiography is simply a definite statement of the meaning of the word Physiography (§§ 1, 12).

7. Use of the Senses. — Our senses are windows of knowledge through which alone information enters the mind, and through which alone we are able to study the things outside us. Instruments and apparatus of various kinds are of value only in making the evidence of the senses more precise or more appropriate to the object of study. All the senses — sight, hearing, touch, and the less used smell and taste — are limited in their scope, and liable to get out of order through disease or neglect. But even when in full health and within their own range they are not quite trustworthy. If an object present different appearances when looked at through different windows, we are justified in supposing that the windows are not equally trustworthy. A few simple experiments show us that this is the case with the windows of knowledge. Every one is familiar with optical illusions proving the imperfection of the sense of sight. A coin spinning quickly looks like a hazy sphere, but we know it to be a flat disc. Strobic circles which seem to whirl rapidly when the card on which they are printed is moved slightly, and designs appearing in their complementary colours on looking at a blank wall have been made familiar by their use as advertisements. Mountains seen in front look steeper than they are ; in a haze on a snowy plain a mouse close at hand has been mistaken for a distant musk-ox, and familiar objects are often passed unrecognised in unusual places. One well-known experr ment shows that touch is as fallacious as sight. When a pea or small ball is rolled on a table by the middle finger crossed over the forefinger of the same hand, so that both fingers touch the object, the impression produced is that there are two peas, not one. Similarly if one hand has been held in hot water and the other in cold water, and then both are plunged into a mixture of hot and cold, the mixture will be pronounced cold by the hand previously heated and hot by the chilled one. The deceitfulness of the senses may impose upon the most acute and practised mind if taken unawares. When Sir Humphry Davy discovered potassium he showed a piece of it to Dr. Wollaston, one of the most accurate observers who ever lived. Wollaston saw the silvery lustre of the new metal, weighed it in his hand and said, “ How ponderous it is ! ” Davy in reply threw the metal into a basin of water, where it floated lightly on the surface. Wollaston’s illusion is the more striking because at that time he was the only man who was in the habit of handling platinum, a metal which, bulk for bulk, is twenty-five times heavier than potassium.

8. Use of Reason. — In spite of such cases of deception, we trust our senses and are rarely deceived by them. Reason, man’s supreme gift, examines, weighs, extends, and judges the evidence of the senses. It requires a course of reasoning to let us know that a tall man far off on a straight road is not a dwarf close at hand, or that the Moon rising behind a wood is not a yellow plate hung in the trees. Long practice has made the operation of reason so swift and smooth that we are seldom conscious of an interval between seeing and understanding. Reason makes the senses satisfactory means for acquiring knowledge, although reason alone can give no information about natural things. Just as the senses maybe greatly aided by instruments and apparatus, reason may be greatly aided by mathematics. And as accurate measurements, on which the value of all scientific observations depend, can only be made by means of suitable apparatus, sometimes of a very elaborate nature, so accurate reasoning, which is essential in all scientific discussions, can only be fully carried out by mathematical processes which are sometimes difficult and complicated.

9. Common Sense is the name which practical people give to the faculty of getting directly at the truth of a question without reference to prejudices, and keeping free from fallacies. Common sense consists of reasoning on the evidence of the senses, but without keeping account of the process. When this common-sense method is made precise and accurate, it becomes the Scientific Method of gaining knowledge. The two guardians of thought in science are Accuracy and Definiteness. The scientific man deals with phenomena as the banker does with money, counting and recording everything with scrupulous exactness. The student should remember that for the practical purposes of life the knowledge of what are called scientific facts is unimportant compared with the power of using the scientific method. It is really more scientific to repeat a quotation from a political speech correctly, or to pass on a story undistorted, than it is to know of the rings of Saturn or the striation of diatoms.

10. Accuracy in observation usually takes the form of

CHAP.

correct measurement of mass, space, or time, by means of suitable instruments. Accuracy is always to be striven for, but it can never be attained. This fact is only fully realised by scientific workers. The banker can be accurate because he only counts or weighs masses of metal which he assumes to be exactly equal. The Master of the Mint knows that two coins are never exactly equal in weight, although he strives by improving machinery and processes to make the differences as small as possible. When the utmost care is taken the finest balances which have been constructed can weigh i lb. of a metal with an uncertainty less than the hundredth part of a grain. In other words, the weight is not accurate but the inaccuracy is very small, and its greatest possible amount is known to less than 7 o CM) oo' Part the mass weighed. In weighing out tea or sugar a grocer is content if the inaccuracy is not more than about of the mass. No person is so stupid as not to feel sure that the height of a man he sees is between 3 ft. and 9 ft. ; some are able by the eye to estimate the height as between 5 ft. 6 in. and 5 ft. 8 in. ; measurement may show it to be between 5 ft. 6| in. and 5 ft. 7 in., but to go closer than that requires many precautions. Training in observation and the use of delicate instruments thus narrow the limits of approximation. Similarly with regard to space and time, there are instruments with which one-millionth of an inch, or of a second, can be measured, but even this approximation, although far closer than is ever practically necessary, is not accuracy. In the statement of measurements there is no meaning in more than six significant figures, and only the most careful observations can be trusted so far. The height of Mount Everest is given as 29,002 ft. ; but here the fifth figure is meaningless, the height of that mountain not being known so accurately that two feet more or less would be detected. Similarly the radius of the Earth is sometimes given as 3963-295833 miles, whereas no observation can get nearer the truth than 3963-30 miles.

11. Definiteness in thought and description does not require perfect accuracy in observation. We must always be definite in order to be clear. If he wishes to be definite in thought the student must never rest content with the dubious “I think” or the vague “about,” but endeavour after the clear “I know” and the precise “with a probable error of.” Vagueness and indecision are utterly foreign to the scientific method. It often happens that there is no definite knowledge concerning some fact ; then all that the scientific method of description permits is to say, “ There is no information,” and to wait until the scientific method of observation has found out something. The difficulty is not overcome by guessing, or by calling the unknown unknowable. There is a place for speculation and imagination in the scientific method (§ 18), but it is a place apart, which must be shut off, for if speculations are not kept in strict quarantine they are certain to infect our conceptions of facts with their own fatal vagueness.

1 2. Scientific Terms. — Definite words are necessary for the expression of definite ideas, hence scientific terms have to be employed. A term has one definite meaning which does not change with time. The rush of affairs drifts words from their original meanings, as ships drag their anchors in a gale, but terms sheltered from common use hold to their moorings for ever. The word let , for example, has drifted in 200 years from meaning hinder until now it means permit ; but the term bisect has remained unaltered in significance for twenty centuries. Many scientific terms are derived from the Greek and have an unfamiliar appearance ; a list of all those employed in this book, together with their derivation, is given in Appendix III.

13. Classification of the facts and processes of Nature is necessary before we can form definite ideas concerning them ; but the definiteness of classification is an artificial restriction. In Nature one thing merges into another by imperceptible degrees, and although, for example, we can readily class typical metals and non-metals, typical igneous and sedimentary rocks, typical plants and animals, there are in each of these pairs of classes many cases which cannot be referred with certainty to either side of the dividing line. Nature is discrete only within certain limits, and its classes are never so definite as to isolate one from another, the unity of Nature being as marked as its diversity.

14. Natural Law is the order in which things have been observed to happen. The fact that there is order and not chance in the way things happen is one of the chief discoveries of science. It is the discovery on which all science depends, because knowledge could never be definite and accurate if it were not based on orderly phenomena. It is impossible that there can be any exception to a law of Nature, or any contradiction of it. Much has been written as to the impossibility of miracles because they would be breaches of the laws of Nature. If there is evidence, however, that a miracle did happen, the law of Nature it appears to contravene must be restated so as to take account of the new phenomenon. It is because the law expands to admit apparent exceptions that we say there can be no exceptions. We have, strictly speaking, no right to assume that things will continue to happen in the order in which they have happened hitherto. Nothing in time past has been more regular and uniform in its recurrence than the appearance of the Sun rising and setting. This regular order is a natural law, yet we cannot say certainly that the Sun will rise to-morrow ; merely that its rising is very highly probable. The law of gravitation, the laws of heat, light, sound, and of all other observed facts, are similarly the summary of observations in the past ; and although each new verification increases the probability that the laws will continue to hold good, that probability never becomes certainty.

15. Probability. — The probability of 7,000,000 to 1 is so great that all but very cautious people think of it as certainty. It represented the chance of a passenger arriving alive at the end of a railway journey in the United Kingdom in the year 1890. The probability that the Sun will rise to-morrow is far greater than this, because no failure has ever been recorded in the past. The laws of Nature, although only expressions of very high probability as regards the future, may be assumed as quite certain for all the practical purposes of life.

16. Cause and Effect. — The relation of Cause and Effect is the fundamental law of Nature. There is no recorded instance of an effect appearing without a previous cause, or of a cause acting without producing its full effect. Every change in Nature is the effect of some previous change and the cause of some change to follow ; just as the movement of each carriage near the middle of a long train is a result of the movement of the one in front and a precursor of the movement of the one behind. Facts or effects are to be seen everywhere, but causes have usually to be sought for. It is the function of science or organised knowledge to observe all effects, or phenomena, and to seek for their causes. This twofold purpose gives richness and dignity to science. The observation and classifying of facts soon become wearisome to all but the specialist actually engaged in the work. But when reasons are assigned, and classification explained, when the number of causes is reduced and the effects begin to crystallise into essential and clearly related parts of one whole, every intelligent student finds interest, and many, more fortunate, even fascination in the study.

1 7- Inductive and Deductive Reasoning. — Reason may be applied to the study of facts in two different ways. Inductive Reasoning is the arduous process of finding the meaning of phenomena by collecting and classifying facts and thinking out their causes. Deductive Reasoning is the shorter operation of finding what effects must result from the operation of a known cause. It is often supposed that since we can observe facts alone the inductive method of reasoning is the only one which can be employed in studying Nature, but the number of facts even in one small department is so great that life is not long enough for the labour of collecting, classing, and discussing them all.

18. The Scientific Method of discovering the causes of phenomena involves the use of both inductive and deductive reasoning linked together by imagination, a mental power which is as essential to the scientific discoverer as it is to the poet. After observing a considerable number of facts the investigator imagines a possible cause or explanation, io The Realm of Nature chap.

and this possible explanation is termed an hypothesis. Then he reasons deductively from the assumed explanation, usually employing mathematics for the purpose, and so arrives at a number of additional facts which must exist if the hypothesis be true. These predicted facts may not be familiar or may not occur naturally at all. In the latter case it is necessary to seek them by making experiments , and so important is this aid in some cases that the expression Experimental Science is often used in the sense of physical science. If the facts predicted to exist in certain circumstances by hypothesis are not found, and if others which the hypothesis could not account for appear, the hypothesis is proved to be erroneous, or, at least, incomplete. Renewed inductive reasoning from the wider basis of ascertained facts must then furnish material for a fresh effort of imagination and a new hypothesis to be similarly tested, and, if necessary, rejected in turn. Should the facts agree with those deduced from the hypothesis there is a probability of its being true, but a great many tests must be thought of, applied, and found realised before the hypothesis is accepted as a true and complete explanation. An explanation of facts found, tested, and proved to be true and complete in this way is called a theory , and when a theory is confirmed by a great number of observations it is accepted as a Law of Nature.

19. Proof of a Theory. — The process of testing an hypothesis requires great caution in order to prevent mistakes. A long time and the labour of many observers are often necessary to perfect a theory or demolish an incorrect hypothesis. When Newton imagined the hypothesis of universal gravitation, according to which the force that causes a stone to fall to the ground also controls the motion of the Moon round the Earth and of the Earth round the Sun, he deduced from the hypothesis that the Moon in its orbit should fall toward the Earth 16 feet in a minute. Careful observation of the Moon’s motion showed that it was only bent toward the Earth 13 feet in a minute, and therefore Newton abandoned his hypothesis as untrue. Thirteen years later Picard’s measurement of the size of the

Earth, and consequently of the distance of the Moon, gave him more accurate data, and applying these to his hypothesis and to the observations, he found that the discrepancy vanished. This assured him of the truth of his hypothesis, which has ever since taken rank as a theory and a law of N ature.

20. Test of a Law of Nature. — A law of Nature has no exceptions (§14); the only test by which a theory can be accepted as of this rank is the successful prediction of future effects. The theory of gravitation enables astronomers to calculate the relative position of the Sun, Moon, planets, and stars as seen from all parts of the Earth’s surface. This is regularly done by a government office in London, and the positions for stated times each day are published three years in advance in the Natitical Alma?iac. From the tables of this work the captains of ocean-going vessels are able to work out their exact place on the ocean by observations of the positions of the heavenly bodies (§ 92). The smallest deviation from truth in the expression of the law of gravitation would throw the results into confusion and lead to almost certain shipwreck. No such confusion has ever occurred, and every successful sea-voyage is one proof more that the law of gravitation was fully understood in the past, and holds in the present. The appointments made for the appearance of the Sun, Moon, and planets amongst special groups of stars at definite times in the Nautical Almanac are analogous to the appointments for the arrival of trains at stations made in official railway time-tables. Observation of the fulfilment of time-table predictions very soon demonstrates that the hypothesis in accordance with which they are framed is not exact, and cannot be depended upon for timing watches or determining our position on the Earth.

21. Magnitude of Nature. — The Scientific Method is applicable to the acquisition of knowledge of any kind, but it has been most used in the study of Nature. It is necessary that each scientific investigator should confine himself to one department of Nature in which he finds the facts and tries to reason out the theories connecting them. Thus we

CHAP.

I 2 are apt to form the impression that Physics, Chemistry, Astronomy, Geology, Geography, Meteorology, Biology are definite sciences, distinct from each other, dealing with different orders of facts which are accounted for by independent theories. These sciences do not completely cover the

Fig. i. — Inter-relation of the Sciences.

field of Nature as the coloured blocks of counties do the map of England. They traverse the field rather like the railway lines which radiate from London. The main line of each science is distinct and easily followed, but the branches interlace with one another in a very complex manner, and though the network is very comprehensive, a mere fraction of the vast surface is after all covered with the lines of definite knowledge. The inter-relations of the sciences are shown in

I

The Study of Nature

T3

Fig. i by representing each as a circle cutting all the others, for on the outskirts of every science there are regions in which another science shares the explanation of phenomena. Chemistry, for example, is called in to aid astronomy in interpreting the spectra of the stars, to aid geology in explaining the composition of rocks, to aid biology in determining the changes of substance in living creatures. Physics or Natural Philosophy in a sense includes every other branch of physical science, although portions of Biology and Geography extend beyond its limits.

22. Physiography and the Special Sciences. — By

division of labour the various parts of a watch are constructed by different workmen, and by the specialisation of science the different realms of Nature are explored by different investigators. In order to have a watch, however, the results of divided labour must be combined, and in order to have a just conception of the Universe the results of specialised research must be fitted harmoniously together. This is the function of Physiography, which has consequently a unique value in mental training, being at once an in troduction to all the sciences and a summing up of their results. It enables a beginner to obtain a quicker insight into any of the special sciences and a fuller grasp of it, while at the same time a student versed in any one special science is enabled to appreciate far more fully than an unversed one its relation to all others and to the system of the Universe.

23. Physiography and Nature. — The natural Universe may be compared to a gorgeous carpet of rich design. In order to understand such a web we might follow out the pattern thread by thread. Selecting first a red thread of the weft, we notice how it passes above and below the threads of the warp, across the fabric and back again, to and fro until the end. Next a blue thread maybe followed in the same way, and so with all the separate colours. The course of each thread has explained something, but the results of all must be brought together to give a complete explanation. In some such way each special science unravels one of the threads of the Universe, but that thread is

14 The Realm of N attire chap, i

so interwoven with the clues of other sciences that a general knowledge of them all is necessary to understand the effect produced by one. Pursuing the simile a step farther, we may note how one observer sees in the rich world-carpet nothing but a number of coloured threads intricately interwoven ; the taste of another is so much gratified by the colour and design that he enjoys the beauty without thinking of the parts or the process ; while a third loses sight of material and beauty alike in admiration of the genius of the designer and the skill of the craftsman. Thus the typical man of science, poet, and theologian look differently on the multiform unity of Nature, which has a true though different meaning for each.

T. H. Huxley, Science Primers — Introductory. Macmillan and

Co.

W. S. Jevons, Principles of Science. Macmillan and Co.

Chapter II The Substance Of Nature

24. Matter. — Diverse and innumerable as the things around us seem to be, the number of kinds is reduced greatly when they are tested by tiying to destroy them. Only what cannot be annihilated is real, according to our definition (§ 5). Tested thus, air, wood, marble, vinegar, to take a few random examples, appear unreal, for they can be produced and destroyed. Closer study shows that though burning destroys both wood and air it produces at the same time other things — ashes, water, carbonic acid, nitrogen — exactly equal in amount though different in properties. Vinegar and marble are both destroyed by mixing them, but other things — calcium acetate, carbonic acid, water — appear in exactly the same amount. So with all the things we see or feel, their properties and appearance can be completely changed, but the amount of substance that exists in them cannot be increased or diminished by any power which man has learned to wield. Substance is thus a real thing, of which air, wood, marble, vinegar and the rest are kinds. The term Matter is applied to everything, however diverse in appearance, which we see and touch, as Man is the term used to include eveiy human being in the world. The difference between some kinds of matter is as slight and superficial as that between soldiers and chimney-sweeps ; between other kinds it may be compared to that which separates Europeans from Negroes.