5 1 w/ji 1 j 9 LIBRARY THE UNIVERSITY OF CALIFORNIA SANTA BARBARA PRESENTED BY RAYMOND WILDER ^n i i / LZlEj 1 SANIA BARBARA L__ I 3 >TTl 8 * AiiSMAJNrt 3*1 c . Tut UNIVcRSITv s rk- 5 % 5 SANS* 9ASAftA s m x*""^ > \ IS'TY ?' " VriTri.t- / iftMTA t.AKBAKA c BI GEOMETKY IN MODERN LIFE. TWO LECTURES AT ETON. iGEOMETRY IN MODERN LIFE^ BEING THE SUBSTANCE OF TWO LECTURES USEFUL GEOMETRY", GIVEN BEFORE C|re Sftterarg j&arietij at tott. J. SCOTT RUSSELL, M.A., F.R.S., ETC. ETC. ETC. ETON: WILLIAMS AND SON. LONDON : SIMPKIN, MARSHALL, AND CO. 1878. LONDON : E. CLAY, SONS, AND TAYI.OP, BREAD STREET HI I.I, E.C. "l8otvaio<; to tyevBo? Kal 6 (pOovos ivri Philolaus, Frag. Kal to pev Br) irpo tovtov irdvra TavT e^etv aXoycos Kal dpeTpcos' ore B' eVe^etpetTo Koapelcrdai to irdv, irvp irp&Tov Kal vBcop Kal ev eypvTa avTcov aTTa, iravTairacri p,r)v BioKeipeva gj 7rav oTav dirfj twos 6Je6?, ovtw Brj totc Tre 777)05 vpd<; BrjXovu. dWd yap iire\ peTe%eT twv Kara iraiBevaiv 6B5)v, oY wv evBeiK- vvoQai Ta Xeyopeva avdyKrj, ^vve^eade. Plato, Timceus, p. 53, B. PREFACE. The two separate views of Education in Science, which are expressed in these pages, will I doubt not be entirely approved by the experienced teachers to whose pupils they are addressed. Geometry, as a pure Science, gives logical training, is a discipline of thought, is an instrument of human culture, and has high educational value. But Geometry is equally the development of a method pervading Nature ; its mastery gives Man a power to govern Matter. The training, which enables him to comprehend the mechanism of the universe, enables him also to make creations of his own in harmony with those greater designs of which his own are but a small portion. These two uses of geometric education, the one purely gymnastic, the other practical and technic, may be so viii PREFACE. combined that each shall aid and not impede the other. The order, number, arid measure which per- vade the universe can be easily brought within the scope of elementary education, and so form the fit preparation for scientific observation and experiment in later life, by means of which the standards of application of abstract truths to matter and events in human life are determined and made familiar. But the one learning cannot be too soon begun, nor the other too long continued, and each is a material aid to the other. Whoever has had experience of the difficulty with which entirely new thoughts are conveyed into the youthful mind, will frankly agree with the author in the absolute necessity of initiating new knowledge in simple words and self-evident forms, and of making meanings plain by repetition and emphasis, in a degree which may seem to the initiated tedious and useless. In this little work there is much, in matter and in manner, open to this just criticism. On the other hand it must not be forgotten that the aim and purpose of preliminary education is "to lead the mind on from simple beginnings to arduous conclusions " ; and for this object and with these PREFACE. ix views the first steps must before all be made secure and unquestionable. In like manner it may be found that while much at the beginning seems too simple, much towards the end will inevitably be too recondite and inaccessible. The highest education of our time will be that which combines the literature and philosophy of the past with the science and arts of the present, and so enables us to forecast, plan out, prepare, and execute skilful, wise, and useful work in the future. CONTENTS. I. THE GREEK PHILOSOPHY AND GREEK GEOMETRY. Antient Philosophy and Modern Science are not antagonistic in Use or Nature, although often so represented in Argument Equally in both, Order, Measure, and Number rule the Universe They applied the Laws of Mind to Matter We seek the Laws of Mind through Matter Page 1 II MODERN SCIENCE AND MODERN GEOMETRY. The Modern Sciences are Methods of questioning Matter for useful Knowledge, and the Modern Geometry contains the Methods of using matter for man's material work in daily life Why is Geometry little known ? Page 8 III. GEOMETRY ANTIENT AND MODERN. Some great Antient Geometers and their works The greatest part of their writings destroyed by fire in the Alexandrian Library Modem Geometers have first tried to restore the lost Ancient Geometry Next to extend it and apply it to Modern Use Geometry, a Study A Science An Art A Tool of the other Sciences .... Page 14 xii CONTENTS. IIII. USEFUL GEOMETRY. Uses of Geometry In Mental Training In Science In Laws of Light and Visible Form In Measuring and Mapping In Ordering, Arranging, Planning, and Building Training for Trades and Professions .... Page 22 V, FIRST STEPS IN GEOMETRY. Here There Yonder Hence Thence Hither Thither Starting Point Stand Point Midway -Measure Distance . . Page 27 VI. FIRST WAYS IN GEOMETRY. Straight On Right Across Forwards and Backwards Right and Left Upwards and Downwards North and South East and West '. Page 35 VII. LAND-MEASURING. Base Line Starting Point Stand Point Stations Chain Measure Off Sets Cross Measures Acres Records Plan Calculations Map Page 44 VIII. THE GEOMETRY OF THREE WAYS. Three Stations Three Ways Three Distances " Trigonometry" On the Square On Ihc Skew Page 56 CONTENTS. xiii Villi. THREE POINT MEASURE. Geometry of Navigation " Trigonometric Surveying " Geometer's Fore- cast " Trigonometric Tables " " Trigonometric Diagrams " Sailors' Trigonometry Page 65 X. MEASURE AND NUMBER. Measures make Numbers The Measure is One Another of the same makes Two The Usefulness of the Number Two In Parting In Cutting In Ways In Navigation In Matter Nature In Music Number Three Number Five Even Numbers Odd Numbers Groups of Numbers Square Numbers Uses of Numbers in Geometry of Place, Order, and Shape, Ordering, Building, Enlarging Shapes by Numbers Movements, in Space by Number .... Page 74 XI. FAMILIES AND PEDIGREES OF NUMBERS. Common Numbers Selected Numbers Choice Number Agreeing Numbers Family Numbers Prime, Patriarchal, Primitive, or Princely Numbers II, III, V, VII, XI Their Families . Page 106 Table of Degrees of the First Five Families Page 116 Pedigrees of the First Numbers \. . Page 123 Table of Sixty -four Family Pedigrees Pages 132, 133 XII. SYMMETRY, HARMONY, MELODY. Symmetry Harmony Melody Page 135 Note Page 141 Table of Melodic Sounds Page 154 Tables of their Numeric Pedigree ........ Pages 133, 156 Symmetry in Work Divine and Human Page 157 Examples of Symmetric Form growing out of the numbers II and V in their Families Page 162 xiv CONTENTS. XIII. SIGHT, LIGHT, SHAPE, AND SHADOW. Light goes Straight We see Straight Light marks out lines for the Geometer An Etonian Geometer in his yacht in Northern Seas finds his place by. Geometry How to shew on paper the shapes of things you see as they seem to eyesight Artists should be Geometers A great Artist Geometer Page 164 XIIII. GEOMETRY, MATTER, FORCE, AND MOTION. Forces and Motions in Worlds of Matter obey the laws and follow the lines of the Geometer The Geometer's Diagrams and Forecasts on pages 70 and 71 are also Diagrams and Measures of the Forces and Motions of Matter in Nature Page 178 XV. ENDING ENDLESS. The Straight The Bent The Crooked The Curved The Infinite The Infinitesimal Page 189 ERRATUM. Page 43, line 3 from bottom, for " October,'' read " September." GEOMETRY IN MODERN LIFE. GEOMETKY MODEEN LIFE THE GREEK PHILOSOPHY AND GREEK GEOMETRY. I hope no Eton Man will think that because I am invited here to speak in favour of Geometry, as a Science of which much Practical Use may be made in Modern Civilized Life, that therefore I undervalue in my own mind or wish to depreciate in yours the Studies of Antient Language, Literature, Politics and Philosophy which form the Classical Education of this famous School of Young Englishmen No ! 1 love Greek Literature, I delight in the Records of Greek Thought I was early a disciple of the School of Plato an early student of Science as taught by Aristotle. If I have learned to think truly and to reason wisely and to follow out principles into acts of life and their due results in human 2 GEOMETRY IN MODERN LIFE. progress, I owe my initiation into right ways of thought and right principles of procedure chiefly to an early training in Greek Thought expressed in the words of the Greek Schools of Philosophy of some 2000 years ago. I therefore love the Literature which is a main subject of your thought and work at Eton aud if I venture to make any suggestion to you, it would be rather that you should carry out your study of Greek Thought and Philosophy to its fit developement, in its due application to our new conditions of Modern Life, Modern Science, and Modern Civilization ; and not at all that you should abandon or curtail any portion of the Mental Gymnastic which you are now going through as a training for life. Allow me to tell you that Modern Chemistry is but a realization and a materialization of the Antient Greek Thought about the Constitution of the Material Universe. Modern Chemistry is the creation of John Dalton John Dalton discovered that all Matter is made up of little Atoms that these atoms, though not alive, have each a little nature of its own, and if not a will, at least a way of its own These atoms are not a confused mass as you might think them when you look at a rude stone or a lump of clay or a sand hill on the sea shore Every rude mass, when you look close into it, is built up of exquisitely made little particles, nicely shaped, neatly fitted GEOMETRY IN MODERN LIFE. 3 together, and all grouped about each other in regular proportions, and although all alike in certain ways, yet so invented contrived and shaped and propor- tioned that out of simple elements you can form endless beautiful combinations. Now, of these pretty little particles, out of which the whole Earth and Heaven, Sea and Air are formed there are about 64 sorts or kinds. Some of these sorts love each other and cling together some hate each other and keep apart. But the strangest thing of all is that each Family or Eace of Atoms, out of these 64 families, has a name or rather a number, which it takes by nature, and it will take no other. By this it rules its conduct, and if forced for a time to group with one it does not like, will break away from it on the first chance and take back to its old companions. Now among these 64 families of elements which make up our World and some of which inhabit the Moon and the Stars also some love the number 3 some love 4 others love 5 or 6 and some take to 7. LOVES OF THE ATOMS. Among the Elements of the World Oxygen loves the number. . 8 Nitrogen loves the number . 7 Carbon loves the number . . 6 Boron loves the number . . 11 B 2 6 GEOMETRY IN MODERN LIFE. also pervades the living mind of Man, made Divine by its divine origin. - -Greek Philosophers then believed in Divine Intention pervading Creation ; in Divine Science Containing The Mysteries of the Thoughts of that Divine Mind. They believed that Humanity is but a Micro- cosm of that Divine Mind They believed that the Thoughts of God, carried out in Creation, are expressed in it in a manner meant to be intelligible to the human mind They believed that the Mind of Man, through the Divine Nature planted within him, has the germs of Divine Truth inherent in his nature, and is able to detect in the Harmony of Man's Nature with Matter Nature, the Harmony of both with the Mind of God ! Now if I am asked which was the Great Antient Science by which the Ancient Philosophers expressed their thoughts concerning the Divine Methods of thinking out the Universe and working out the Matter World I venture to say, that the Method which led them to the Truths of Creation and Com- prehension of God's Truth, was, the Antient Geo- metry. Now do not understand that when I speak of the Antient Geometry I am thinking of Euclid only. The burning cf that glorious treasure house of human and divine thought the Library of Alexandria some 1,200 years ago was an incalcul- able misfortune to modern scholars and to humanity. Euclid's books were a part and but a small part of Antient Geometry, and much of his work was GEOMETRY IN MODERN LIFE. 7 burnt and lost of the fragments saved no one can esteem the value more than I do, as the spark of fire that has rekindled Modern Science. I say then that Euclid's books are to us a valued treasure of Greek Philosophy but only a fragment of the Divine Literature of Greek Philosophy a guide, through the first steps of the exact thinker, groping his way to the Governing Truths of the Universe of Matter and its Divine Mind. GEOMETRY IN MODERN LIFE. II. MODERN SCIENCE AND MODERN GEOMETRY. Modern Life is distinguished from Antient Life mainly by the Developement of Thought and Thinking into Act and Work The Antients thought and sang and philosophised, and it is our delight to read their thoughts in their clear Logic and chant their songs in their living poems They created Deities out of their own heads and built up an Ideal Universe out of their Creative Genius We Moderns owe them much They have taught us to think and reason they did more they taught us to embody thought in Matter Their Sculpture and their Architecture are embodiments of refined thought cut with exquisite skill out of shapeless masses of stone and marble. But Modern Life and their Life have little in common beyond community of thought and feeling The things and works of our life and theirs are radically different We start life in their grooves of thought and we straightway diverge into modern ways of thinking and working. GEOMETRY IN MODERN LIFE. 9 Geometry is one of the links that binds us and them together Euclid has survived as well as Homer The Conic Sections of Apollonius and the Helix of Archimedes, are the staple of modern astronomy and modern mechanics Their thoughts and their ways of thinking are indeed our heritage. But all the uses we make of Thoughts and Thinking are quite different from theirs They created Divinities out of their own fancy We seek Divinity in deeds not fancy "We seek a Deity, in a Power that creates worlds and makes them carry themselves, with no need of a fancied Atlas to carry them on his own shoulders We seek a Deity in a Practical Ruler of the Universe Whose Will gives changeless Law to Matter and to Mind In Whom we live and move and have our Being Who prepared us to live in this World, and Who prepared the World for us to live in. Who put in the World stored for us Stone to build with, Coals to burn, Iron to melt, Brass to mould, Steel to cut, Water to drink, Air to breathe Who covered the Earth with green carpets, and raised noble woods above to shelter us, and dressed lovely flowers up for our joy ; and bade the trees prepare fruits and strew them along our paths and set us in a Paradise. We seek also a Divinity to Whom we have some near affinity Who made us in His own image, so that we too are Divine Who has placed us here in this beautiful Earth to make it more beautiful Who has given us all its treasures that We might show our divine nature by doing 10 MODERN SCIENCE all the work in the world which He left undone in order that we might do it He gave us gardens, trees and flowers, that we may also make gardens, trees and flowers, and make them more beautiful than we found them and we have done so in a measure by modern horticulture and make lands more fertile and fruits more fruitful, which we have done by modern agriculture. He gave us horses to carry our burdens and oxen to draw our ploughs, and left us to make horses much more powerful, and ploughs much more helpful, which we have done by making engines every one as powerful as many horses, and each fleeter than the fleetest racehorse and by setting other engines, instead of oxen, to plough our fields, and dig our mines, and drain our marshes, and spin our yarn, and weave our clothes. Thus we now rejoice, in a nobler Divinity than the Greeks, and we have a nobler vocation than theirs, the vocation of Acts and Deeds and Works which carry out the aims ot the World Maker as far as made known to us little men who try to become worthy of our divine pedigree. Thus then we have thoughts in common with the great thinkers of old But we differ from them in our acts We think that we were set in this world for a purpose That we were destined to work out part of a great plan That our part of that plan is to make perfect all the work for which the materials have been collected, arranged, and stored up for AND MODERN GEOMETRY. 11 us and that work Modern Science enables us to fulfil, that work we are busy doing. Now the Great Instrument the Divinity has used in creating our world is Geometry. The Tool He has given to us for our work is Geometry. This Instrument we owe to the Antients who told us, " God is the Great Geometer." The Use of this Instrument they commended to us when they wrote over the Schools of Greece, " Let no Ignoramus in Geometry enter here." D MHAEIS AfEnMETPHTOZ EIZITI2. D If I were asked to define Modern Geometry I should call it the " Science of Shape." Perhaps I should add to its fulness by adding also Size as well as Shape ; but we might consider Size as an Element of Shape. If I were asked to extend and explain my Definition, I should say that Geometry Compre- hended all Knowledge of Space and Place Distance and Measure Direction and Way Shape and Size Bulk and Extent ; I should further define Geometry 12 MODERN SCIENCE as an Art as well as a Science. The Antients called it Earth Measuring But we Moderns use it for Sea Measuring as well as Land Measuring, and for Sky and Star Measuring equally. But it is much more than this It comprehends the whole of the Arts of Shape Design Shape Drawing Shape Cutting Shape Building Shape Creating. But Science and Skill in Shape Making is really the Essence of most of the important Arts of common life We take shapeless clay and shape it into bricks we take shapeless piles of bricks and shape them into shapely Queen Anne's palaces we quarry masses of stone and our masons hew them into columns, arches, palaces and churches we give a block of marble to the sculptor and he gives it us back a Venus de Medicis or an Apollo Belvidere we give a shipwright great trees and he shapes them into sea-going ships we give the goldsmith an iu sot of cold and some stones and he gives back a princely crown our potters and glassblowers give shapes to marvellous dreams and produce triumphs of Art in form and varied hue. All modern work is but the transformation of some mass of Matter out of one shape into a better shape. Geometry is of the Essence of Modern Life If Geometry thus pervades everything round about us were it not well that We should all of us know something about it \ If most Work done in the world of Matter is merely trans- formation of Shape, should not each of us make himself more useful to the world if he knew how to AND MODERN GEOMETRY. 13 transform things out of the shapes one doesn't want into the shapes we need ? The best answer to all this is given by the Antient Greek " God is the Great Geometer." Let us be little ones ! But if Geometry be thus the One Universal Science of the Nature of all the Material World all round about us If it is necessary, in order to explain to us the difference between Things Created and Matter in Chaos before Creation If Creation was merely the Giving Shape and Substance to Things which were formerly without Form and Void it is plain that the chief work of the Matter world comes under the Science of Geometry ! Why then is Geometry to the greatest number of human beings The Unknown, both as Science and Art ? The answer to this is not difficult Geometry is and was always an Exact Precise and Hard Study. Geometry is hard to learn and hard to practice Geometry requires of the learner, self-sacrifice. Geometry requires of the worker, dexterity, exact- ness, Forethought. Thus the nature of Geometry makes it hard to get and hard to use. I will now try to make it more easy for you to learn and more convenient for you to use, by helping you to avoid the crooked paths that confuse the learner, and the clumsy ways that lead him to do bad work. 14 GEOMETRY IN MODERN LIFE. III. GEOMETRY ANTIENT AND MODERN. Geometry as we now have it, is almost wholly the Antient Geometry. But the aims of Modern Life and the uses to which we put the knowledge the Antients have left us are new and manifold. Geometry as a study is now twofold, a Science and an Art. As a Science we have little more to learn than what the Greeks knew and taught. As an Art, useful in modern life, we have done much and have still more yet left to do. Unluckily for us, we have only fragments of their knowledge. The work of Modern Geometers has been mainly to seek, gather, and join these fragments, to fill the void spaces, to recover and restore their lost Geometry to its original completeness. That Geometry was the result of 1,000 years of Antient work : and ours is the result of 300 of modern research and restoration. GEOMETRY ANTIENT AND' MODERN. 15 Foremost among the great Antient Geometers were : OAAHZ. 560 546 B.C. Milesian of Phoenician origin. Founder of the Ionic School. ANAZIMANAPOI. 547 B.C. Milesian. Father of Geography. First Map. Dissertation on Magnitude of Stars. nYGATOPAZ. 539472 B.C. Native of Samos. Migrated to Croton in Italy. Founder of the Pythagoreans. nAPMENIAHZ. 502455 B.C. Native of Elea. Chief of the Eleatic School. Author of Terrestrial Spheric Geometry. 16 GEOMETRY IN MODERN LIFE. nAATnisi. 429 347 B.C. Athenian, born in iEgina. Founder of the Academy. APIZTOTEAHZ. 384323 B.C. Native of Stageira in Chalcidice. Founder of Peripatetic School. EYKAEIAHI. Of Alexandria, b.c. 323. Founder of the Mathematical School of Alexandria. APXIMHAHZ. Of Syracuse, b.c. 287212. Geometer Astronomer Engineer. euprjKa. i o AnOAAHNIOZ Of Perga. b.c. 222. Conic Sections. GEOMETRY ANTIENT AND MODERN. 17 nTOAEMAIOZ. Of Pelusium. a.d. 139. Lived at Alexandria. Geometer Geographer Astronomer Musician. 0EOAOZIOZ. Of Tripoli, a.d. 96 (?). Master of Spherical Geometry. nPOKAOZ. A Lycian. Born at Byzantium, 412 485 a.d. Studied at Alexandria. Taught at Athens. Treatise on the Sphere. ALEXANDRIAN LIBRARY DESTROYED. By order of Khali f Omar. a.d. 640. The Library of Alexandria, said to have contained 400,000 volumes, was divided into two parts. One in the Brucheium, the other in the temple of Serapis. The Library in the Brucheium was destroyed during the blockade of Julius Caesar, B.C. 47. The Serapeion was partly destroyed by Christian fanatics in the fourth century, a.d. It was finally destroyed by the Khalif Omar in 640, a.d. 18 GEOMETRY IN MODERN LIFE. The great Modern Geometers have been GALILEO GALILEI. 1564, a.d. 1642. JOHN KEPLER. 1571, a.d. 1630. RENE DES CARTES. 1596, a.d. 1650. ISAAC NEWTON. 1642, a.d. 1726. G. W. DE LEIBNITZ. 1646, a.d. 1716. BERNOUILLIS. JAMES. JOHN. DANIEL. 1655, a.d. 1782. LEONHARD EULER. 1707, a.d. 1783. GEOMETRY ANTIE NT AND MODERN". 19 During the present century some eminent geo- meters have lived, whose works will form part of the history of our century. I trust also that more eminent geometers may still come forth with great discoveries, some of which may set in order the chaotic accumulations of material facts by special records of minute observations. But it is not our duty here to anticipate the great achievements which may still be left for the young geometers of the nineteenth century. The great codes of Geometric Truth given us by the Antients, and recovered for us by Modern Philosophers, are one of the most important sources of Modern Education. Geometry is a Study. It feeds Thought, with Changeless Truths. It trains Minds to, Methods in Thought. It disciplines character to Precision in Fact, Method in Eeason, Modesty in Opinion. Geometry is a Science, Giving Universal Law to all Space, and to All Matter Filling Space. C 2 20 GEOMETRY IN MODERN LIFE. The essence of Geometry in Matter is to give it Place, Order, and Symmetry out of Chaos, Disorder, Confusion. Geometry is an Art, For practical use in daily life and common things. It teaches, Measuring, Shaping, Planning, Moulding, Drawing, Cutting Out, Mapping, Building Up. Geometry is a Tool of Science. It helps us to measure truly, Lands, Moon, Seas, Stars, Continents, Heavens. The methods of Geometry Explain, the Principles of the Universe. Express, the Laws of Matter, as laid down bv The Great Geometer. GEOMETRY ANTTENT AND MODERN. 21 The Study of Geometry teaching us, the Nature of the Universe, Methods of Construction, Organization of the Matter World, teaches us also, the Nature of the World in which we have to do each his own work : and shews the methods, by following which man may imitate God in giving like perfection to his work. 22 GEOMETRY IN MODERN LIFE. IIII. USEFUL GEOMETRY. We now understand That Geometry is the gift of the Greek Geometers to us, for use in our life That it is the great instrument of Modern Science That without it no man can do good work in the world of Matter in which we each occupy a responsible place. I. Use of Geometry in Mental Training. Teaching to Think Exactly, Word Thoughts Precisely, Reason Truly. Training to Submit Opinion to Fact, Bend Will to Rule, Enforce Law, Maintain Truth. USEFUL GEOMETRY. 23 II. Use of Geometry in Science. Giving Exact Knowledge of P1 aces, Shapes, Distances, Sizes, Directions, Extents, Wa y s > Contents, of all the things round about us, the world at large, the Universe of Space, under the divisions of Surveying, Navigation, Geography, Astronomy. III. Use of Geometry. In teaching Laws of Sight and Visible Forms- Lines of Sight, Lines of Light, Images of Things as Seen, Images of Great and Small, Images of Far and Near. Visible Forms and Tangible Forms. 24 GEOMETRY IN MODERN LIFE. IIII. Use of Geometry. It teaches Measuring and Mapping the Near and Afar- Gardens, Seas, Fields, Islands, Lakes, Continents. V. Use of Geometry. It teaches the Placing of Things Aright, Setting Things in Order, Shaping Things Aright, Fitting Things to Each Other. Forming truly the Straight and the Bend, Square and the Skew, Upright and the Slope, Flat and the Round. It teaches Building up the Great out of the Little, Outtino- down the Great into the Many ; USEFUL GEOMETRY. 25 How the Great grows into the Infinite, and the Small dwindles down into the Infinitely Little. VI. Use of Geometry. It teaches Geometric Laws of Force. Geometry of Balance, Geometry of Movement, Persistence of Force in Line, Persistence of Motion in Line, Deviation of Line by Deflection of Force, Compounding of Motions and Forces, Stored Force, Spent Force, Growing Speed, Steady Speed, Waning Speed, Paths of Projectiles, Pendulums, Planets. 26 GEOMETRY IN MODERN LIFE. VII. Use of Geometry. Geometry gives useful training in the following Professions, Occupations, and Trades. Philosopher Master Professor Teacher. Sailor Soldier Engineer Mason. Architect Builder Plasterer Plumber. Farmer Ploughman Hedger Ditcher. Miner Smelter Mould er Fou n der. Woodman Sawyer Carpenter Joiner. Spinn er Warper Weaver Tailor. Potter Glass-blower Glass-cutter Glazier. Goldsmith Coppersmith Tinsmith Blacksmith. Sculptor Carver Decorator Painter. FIRST STEPS IN GEOMETRY. 27 V. FIRST STEPS IN GEOMETRY. The first Thoughts in Geometry arise in Your Mind and in Mine, when You and I standing apart ask How far asunder are We ? The first Words of Geometry arise when we want to tell each other what we think, about our Places and our Distance I stand Here You stand There. I call the place where I stand " Here," You call the place where I stand " There," I call the place where You stand "There," You call the place where You stand "Here." Thus when we both mean the same thing we two express our thought in opposite words. 28 GEOMETRY IN MODERN LIFE. The Words of Geometry have therefore different meanings and even opposite, according to the place of the Speaker or the place of the Listener at the time the words are spoken. Our first work as Geometers is to give clear meaning to each of the simple words we use. Here ! There ! ! Yonder ! ! ! are the words I use for the Places we two speak of. Here means My Place, Where I stand, My Stand -point ; There means Your Place, Where you stand, Your Stand-point ; Yonder means The other Place, Where the other stands, His Stand -point. Geometers mark these Places thus : My 1 You | Your Stand I Q Q Stand- point I Hero. There I point. FIRST STEPS IN GEOMETRY. 29 Geometric Ways. Hence, Thence, Hither, Thither, are the words for the Ways we think of. We mark these Ways and show them thus : I f Going Coming^ You Q 1 ^_> Thither Hither < & \ Q Here I Hence. Thence There. Thus When I go " Thither," you call it " Hither," When You come "Hither" you call it "Thither." Thus, once more, meaning the same ways, we use opposite words, I calling that way "Hither" which You standing opposite call "Thither." Thus the meanings of Words about Place and Way change with the Speaker or the Listener or their place or attitude. To make words about Place and Way clear and exact, the Geometer first settles one place which he calls the Starting-point, another which he calls a Stand-point, and any or many others which he calls Stations or Marks. 30 GEOMETRY IN MODERN LIFE. His first work is to learn or fix how far the Starting- point and Stand-point are asunder from each. This he sometimes calls his Base Line sometimes he calls it his Standard (stand-hard) of di-stare (di = dwy = two and so apart) or Distance (di-stantia) sometimes it is a very long distance or a short one, a Standard Mile or a Standard Yard or a Standard Inch. Having settled my Starting-point here and your Stand-point there, let us take the first steps to get accurate measure of Far and Near. You standing There, I standing Here, Let us agree to Meet (Mete). Starting Hence I take 1 1 steps your way, Starting Thence you take 1 1 steps my way. We Meet. We call our Meeting Place " Midway." "Midway" between Starting-point and Stand- point is now a settled Station. We call this Midway Station, the same distance from your Place and mine. If our steps agree our Midway is equidistant from our two stations. FIRST STEPS IN GEOMETRY. 31 We must therefore agree our steps. I therefore walk from Midway to your Station and find it 11 of my steps ; you walk from Midway to my Station ; if you find it 1 1 of your steps : we are at one. It is agreed that Midway is 11 steps away from both stations. Whence it comes that Start-point and Stand-point are 22 steps asunder. Start- _ Stand- . O ... ii ...+... ii ... o . point v -^ ^-^ point x <-22-> x An agreed Step is commonly called a Pace. An agreed Standard among English Geometers is called the Yard Measure. An agreed Standard among English sailors is called the Fathom Measure. The Yard Measure measures half-way of the Fathom ; " Two Yards " mean the same distance as " One Fathom." The Basis of all Geometry is therefore a Settled Start-point, and Settled Standard of Distance. 32 GEOMETRY IN MODERN LIFE. England has settled her Start-point, from which she has measured England, Europe, the World, and the Heavens. England's Start -point lies in Greenwich Park. There it is preserved in a national building, in care of the Geometers of the nation. From this Start- point in Greenwich Park all England is measured all English maps are measured and made from this Start-point Maps or Charts of all Seas round the World are measured and made from it, and printed for the use of all English ships and sailors. Wherever an English sailor in an English ship has to find his way across the sea, an English map shows him how he should go showing him how far he now is to the East or to the West of this Start-point in Greenwich Park. On his map this Start-point is marked Q and the other stations are marked & c -> as they go Eastward from Greenwich round the World. 1 England has also settled her Standard of Distance as well as her Standard of Place One English Yard has long been safely preserved by the English nation as the Standard of all English Measure. The English Yard is the Standard of Distance o on Land. 1 These marks show '' Meridians " and give " Longitudes " on Maps and Charts. FIRST STEPS IN GEOMETRY. 33 The Fathom double the Standard Yard is the Standard of Distance at Sea. The English Standard Measure is as carefully kept for the service of the English nation as the English Start-point. The necessity for the establishment of a national Standard of Measure is very plain We cannot all step alike we all want to measure truly, not to take distance as mere guess work, or matter of personal fancy. As men's strides differ in stretch, the English nation found that they must take one man's measure, instead of leaving his own measure to each man's choice. So they took the measure of the King's arm's-length, and agreed that should be Standard English measure. Both his arms out- stretched make the English Fathom, and each one a Yard. That King was Henry I. But the French took the length of Charlemagne's foot as their Standard, calling it pied du-roi. It is also on record that the girdle of the Saxon Kings kept at Winchester was ordered by King Edgar to be the Standard "gird" of English measure, and that it was ordered by William the Norman not to be changed. The English Standard was afterwards deposited in the Crypt Chapel of Edward the Confessor in the Cloisters of Westminster Abbey, and was carefully preserved there till recently, when it was trans- ferred into the keeping of the present " Warden of the Standards." 34 GEOMETRY IN MODERN LIFE. It is instructive to find how man's measures of this world and of other worlds grew out of his own person and his own wants. A sailor measures a line or a rope, by unwinding it, holding a length of it out- stretched between his arms, and then shifting the line length after length until he has measured it all by arm's lengths. To tie a knot at each arm's length was an easy way of marking a line, and at every 11 arm's lengths. Of these arms' lengths, or fathoms, 11 are the breadth of one acre, 110 being the length of the acre ; 880 are an English land-mile, 1014 make a sea mile, and 21, GOO sea-miles gird the globe. The foot, once the " pied du roi," is in England somewhat shorter than the foot of Charlemagne, being | of the fathom, or ^ of the yard. Thus man takes himself as the measure of all things round about him. Perhaps also we Finite Beings can only comprehend the Universe about us by the measure of our own little bodies, little ways, and little minds ! FIRST WAYS IN GEOMETRY. 35 VI. FIRST WAYS IN GEOMETRY. The StartiDg-point in our Geometry once settled, our Measures agreed, our Distance taken in Number and Measure we may now proceed to find our way further on and otherwise. You and I standing apart, I Here, You There ; have paced towards each other 11 paces and have met Midway. Let us now each turn aside. You go to your Right, I go to my Right, or as a third person would say, one go to the Right and number two go to the Left. Let us each make 11 paces and take our stand there turning round face to face. We now face each other, 22 paces asunder. Let us next move towards each other and meet Midway. Let us next return, you to your Left, I to my Right, each to our old place. L> 2 36 GEOMETRY IN MODERN LIFE. Your Second Station. O I O Here Meeting m> Meeting You -O There O My Second Station. FIRST WAYS IN GEOMETRY. 37 What have we done ? We have both paced new ways " Eight Across " our former ways. Formerly, we paced Eight Forward and met Now, we went Eight Across, returned and met. This New Way is called the "Eight Across" to mark its difference from the Eight Forward. Sometimes also we say " Eight On " and " Square Across," meaning the same difference of way. But whatever words we chose, Straight On, and Eight Across are the two first clearly distinct w T ays in Geometric Thought and Work. 38 GEOMETRY IN MODERN LIFE. Your Station. O on? My Starting ^-v Returning Point. -< W Returning Your Starting -O Point. M o My Station. FIRST WAYS IN GEOMETRY. 39 The most perfect means of pointing out these two ways, and marking the nature of their difference to the eye is to take a sheet of paper, with no fold in it, then to double it, folding it flat, and opening it out again, when you see a mark right through the paper. Call that mark a "Line." Next, take the two ends of that line and lay them on each other by folding the paper over. Then press the doubled paper quite flat and open it out again. You will now see two marks going right through the paper and going right across each other. These marks in the flat sheet are two marks of the difference of way called Straight On, and Right Across. 40 GEOMETRY IN MODERN LIFE. be < m Square Across. To the Left. 01 Q Square Across. To the Right. tc - FIRST WAYS IN GEOMETRY. 41 This process of folded measures, may assist us in thinking clearly out the matter of " Way and Measure," as distinguished from our former process of "Distance and Measure." Our first folding of our flat sheet gave us one marked track along the paper. We call it straight along or right along, because it shews no turning aside either way. The sheet of paper on either side seems the same, shewing no difference between one side of the line and the other side of the line. Both sides in the overfold agree and are at one, there is no dif- ference between the right side and left ; and the line continues always right on one way without turning. This therefore we call the Eight Forward or Straight Onward way and line. Our second folding of our flat sheet gave us a second marked track across the former marked track. We call it Straight Across or Right Across or Square Across, because it shews no leaning to either side. Each side covers the other side and so measures it exactly by itself. The two are one they agree. Right Across is the middle way between the two opposite ways. Thus, then, when we call the one way Right Forward we call the second or middle way Right Across Or if we called the one way Right Backward, this same middle way would still be right across the one way, whether you called it forwards or backwards. When we face each other, forwards from you is backwards from me, when ways cross us both, Right Across to you and Loft Across to mo are one. 42 GEOMETRY IN MODERN LIFE. j. a w - E O O 03 P4 fc < O O fz FIRST WAYS IN GEOMETRY. 43 Thus the language of Way becomes settled and clear. And we next ask ourselves Can we have a starting way, just as we had a starting point 1 Can we have a Standard Measure of Difference of Way, just as we made a Standard Measure of Dif- ference of Distance ? The North Pole Star the Eising and Setting Sun, give us our Leading Ways or Starting Directions for our sailing voyages, for our land travels, and for our Geometric Surveys. The Pole Star and the Mariner's Compass shew us the one way of North and South. The rising sun and the setting sun on the 21st March and 21st October, shew us the other way of East and West. And these two ways go Right Across. 44 GEOMETRY IN MODERN LIFE. VII. LAND MEASURING. The ways of the Land Measurer and of other " Geometers/' are reckoned by the methods and guided by the principles we have initiated in our last two Sections. Suppose I want to make the plan of a field ? I first walk round it, and make a sketch on a page of paper shewing the shape it seems to me ; one side may be on the bends of a stream, the other on a road with trees and cottages, that may give it an irregular shape difficult to measure. But I get over the difficulties by the use of the two kinds of line, " Straight Forward " and " Right Across." I take first my stand at a point whence 1 see right through to the farthest off point of the field. I then walk my own measured pace along this line, keeping count as J go, and marking in figures any objects I pass -a tree a stream a fence a path. LAND MEASURING. 45 46 GEOMETRY IN MODERN LIFE. This first measured straight way I may call my Base Line. My Starting-point being at one end and my Stand-point at the other. My measure of this is, say 330 of my paces or yards. That I mark on my plan. Start Bush Oak Station o -o o o 70 60 230 Base. When I have reached my Stand-point at the far end of the field and recorded my distance ; I take that as my Base line. I next proceed to take measures Right Across my base line. These measures taken right across the base line, Land Surveyors sometimes call "Offsets." I take my measures right across as follows. Standing at my far station, I return along my base line. Returning I measure 22 paces backwards. Here I stop. Turning to the right, I walk Straight Across, to the boundary, pacing as I go, and pacing as I return to the base line as a check on my accurate pacing. I mark the measure of this on my sketch, and this I measure off exactly on my plan across the base line to the right. Next I turn to the left of the base line ; I walk straight to the boundary, pacing as I go, mark my measure on the sketch, and check it by pacing as I return. Thus I have measured my first pair of offsets right and left at my first halting-point on my way back along the base line. LAND MEASURING. 47 48 GEOMETRY IN MODERN LIFE. The Second process is like the first. I return along the base line a second stage of 22 paces, stopping at 44 yards from the far Stand-point. Here I pace my second offset to the right and my second offset to the left, and I check both and record them on my sketch. Thus I continue my work without change of method, to a Third, Fourth . . . and Fifteenth Stopping place, recording a pair of offsets at each. I am now at the original Start-point. My work of measure is done. My work of making a plan of the work done still remains. I take a flat board, and a flat sheet of paper stretched on it. I draw a Base Line, I measure 330 equal parts on it ; I call each part a pace, I mark every 22nd pace, and draw a line right across at each mark, going off to Right and Left, and I mark on each and measure on each its recorded length. I place a mark on the end of every offset at its place of measured length. Then I see plainly the outline of the Field truly " marked out " or " set off" by this line of marks. Thus I have a Plan of my Field, recording its measures. But J want to know more. I want to know how many acres my measured field encloses 1 What is an acre ? An acre means the day's work of a plough. What does a plough do in a day ? A good plough covers with a day's work a stripe of land 22 yards wide and 220 yards long, which on water LAND MEASURING. 49 50 GEOMETRY IN MODERN LIFE. would be called 11 fathoms wide and 110 fathoms long. Or if turned into feet it would be 66 feet wide and 660 feet long. That is an Acre. Now in measuring the field, we stopped every 22 yards and took an offset. We cut the land right across by our offsets, into stripes, each 22 feet wide. If then we had 15 stripes of 22 yards wide, and if the average length of each stripe were 220 yards, then our field was exactly 15 acres, and so our work is done. Now the simple result would be quite correct if the offsets had been all alike long, as they would be in a field everywhere the same breadth. But if they varied in length, we have only to add all the lengths together, and we should get the same result, as the longer offsets would make good the defects of the shorter offsets. LAND MEASURING. 51 Record of Measurements. Base line 15 stations of 22 yards = 330. Across Start-point Across. Eight o Left 11 22 13 22 44 23 33 66 34 44 88 59 55 + 110 + 88 66 132 82 84 154 86 90 176 121 73 198 165 63 + 220 + 196 50 242 157 37 264 116 26 286 80 14 300 39 O + 330 + o E 2 52 GEOMETRY IN MODERN LIFE. Calculation of Acres. On the Right of the Base Line. On the Left of the Base Line. I | Completed Stripes. 11 13 24 I 22 23 45 II 33 34 67 III 44 59 103 mi 55 + 88 + 143 + V 66 82 148 VI 84 86 170 VII 90 121 211 VIII 73 165 238 vim 63 + 196 + 259 + X 50 157 207 XI 37 116 153 XII 26 80 106 XIII 14 39 53 XIII1 668 1259 1927 On the Right 668 yards length of Stripe 22 yards wide. On the Left 1259 yards. On the whole 1927 yards length, or 8 acres and | [8.759]. LAND MEASURING. 53 Thus to measure a field, to tell how many acres it covers, you merely cut it into stripes 22 yards broad, and you measure the length of each of the stripes, and you add these lengths all together, and you see how many lengths there are of 220 yards each, and that number of lengths is the number of acres, which gives the following scale of acres. 22 yards Broad. SSL* MHe. Ten Miles. Length of Stripes . 220 440 660 880 1760 17600. Number of Acres . One Two Three Four Eight Eighty Acres. Hence we see that a railway passing through land and taking a breadth, for fences, works and way, of 22 yards, would require eight acres of land per mile of railway. Where the works were small half that would do. This measure of acres of plough fields, and the small measures of cloth, are done the same way. A web of cloth may be one yard wide measured right across its length, and may be 33 yards long. This we call one piece of cloth. We also call it 33 square yards of cloth. A wall we should measure the same way. A 6 feet wall, might measure two yards upright and one mile long. That we should call twice 1760 yards, or 3520 square yards of wall. A window having panes of 54 GEOMETRY IN MODERN LIFE. glass, each 1 foot wide and 18 inches long, of 12 panes in number, would make one stripe of glass, 18 feet long of 1 foot wide measured square across. We should call that an extent of 18 square feet. In like manner a piece of silk ribbon 2 inches wide and 33 inches long would be said to contain 66 square inches, and laid on a piece of cloth that ribbon would be said to cover 66 square inches of cloth. In like manner a stream, canal, or river, might be half a mile wide and 66 miles long : and that water we might say covered an extent of 66 miles long, half a mile wide or 33 miles long of 1 mile wide, or 33 square miles in extent. Thus, the thoughts of " Distance " and " Measure/' " Straight Forward," and " Right Across," correctly warded and properly worked out, give all the knowledge necessary to enable you to do the Geometry of Field and Land and Flood Measuring. All this simple Geometry of the two Elementary ways Straight Forward and Right Across is good for all measures, easily within reach. But when you have to take larger and longer measures, than our own paces can roach, where you have to measure impassable streams, wide lakes, steep cliffs, high mountains, broad sens and distant stars : you luive to seek the aid of LAND MEASURING. 55 instruments of direction and distance, which the Practical Geometer has made, which enable your sight to see afar and to measure afar, distances which your own senses and your personal measures, cannot compass without their aid. Such methods and in- . . , . ( Topographic struments are explained in < ~ I Geometry. 56 GEOMETRY IN MODERN LIFE. VIII. THE GEOMETRY OF THREE WAYS. We have now seen how the Geometry of " The Two ways," The Straight Forward and Right Across enables us to take the shapes and draw the plans and measure the acreage and tell the extent of Fields and Walls, and Stuffs. We have next to study a Third Way the intro- duction of which leads us to another branch of Science. The Geometry of Three Ways. When You and I met face to face I here, You There : when we met midway and measured our distance asunder, we called that the Way from Stand- point to Stand-point. We called it the Right For- ward Way and the Straight Forward Way. When next we Two met Midway, and you turned to the Left while I turned to the Right, and then turned and faced each other, and then returning met each other Midway ; We called that Second Way Right Across or Square Across the former way. THE GEOMETRY OF THREE WAYS. 57 But we may now introduce a third person into our group. We must give him his own Stand-point. This third Stand-point introduces new relations of Place and Way, as Elements of our Geometry. I Here. You There. He Yonder. My Your His Stand-point. Stand-point. Stand-point I. II. III. Now the first question is, where shall we place him ? shall we first give him a Stand-point ? and next let him choose one ? Let us first give him one of our Stand-points, say at the end of our way Right Across. Then he stands where one of us stood, and we three face the same Middle Point. He facing Right Across us. The Three Stations. in o i ii 58 GEOMETRY IN MODERN LIFE. Suppose now we wish to meet. We have only each to march as formerly towards the common Middle-point and we meet and return each to his own Station. Next he may wish to come to me. For this our two ways suffice. He has only to march to the Mid- point, face to the right and he reaches my station, or to face to the left and reach yours. This he does and returns back the ways he came. The Three Distances. m o o < m 1 m > X -< m 10 m > ii o Thus the two ways Right Across suffice for the communication between our three places, until a new question occurs to him. THE GEOMETRY OF THREE WAYS. 59 May / not come Straight from III to I ? May / not come Straight from III to II ? Might you not come Straight from I to me ? Might not he come Straight from II to me ? The answer is " Certainly." It is now plain, that between each couple of us three there is now one Straight Forward way, which makes it unnecessary for either of us to go round by the Midway and then turn right across a second way before reaching the other's Stand-point. Between you li and me I, there lies One Straight unbroken Way. Between you II and him III, there lies One Straight unbroken Way. Between him III and me I, there lies One Straight unbroken Way. 60 GEOMETRY IN MODERN LIFE. Thus these three places, give rise to three Straight Ways. The Three Ways. hi o N* 'r / X [ I The study of These Three Places, and These Three Ways gives rise to what is called, "Trigonometric Geometry." Trigonometric Geometry is the basis of Navigation, and Topography, and our National Trigonometric THE GEOMETRY OF THREE WAYS. 61 Surveys and Maps are conducted by its laws. It is therefore most worthy of study. The Geometry of the Three Ways, starts from the same modes of thought and action, which gave us to understand the Geometry of the Two Ways. When we were only Two, You and I stood apart. We marched and met Midway, measuring as we met. We returned to our former station checking our way as we went back. Now that we are Three, let us do the same thing. Let us two, I and II, repeat our measure. Let us two, I and III, measure our distance asunder, meet and return. You two, II and III, measure your distance asunder, meet and return. We three have now met and measured our Three Ways. Let us now compare together, our original Two Ways, with our new Three Ways. Our original Two Ways made a complete system of communication between the same Three Places as the Three Ways now do. Thus the question arises. Which is the better 1 The Three Ways or the Two ? What are the uses of the one and the other system ? These two systems of Geometric Thought and Work are distinguished by the names the Square and the Skew. We ask, shall we go on the Square or go Askew ? Shall we work on the Square or on 62 GEOMETRY IN MODERN LIFE. the Skew ? Sometimes the system of the Square or Working and Measuring Right Across, is called the System of Rectangular Co-ordinates, and tle other is called Oblique Triangulation. But the meaning is much simpler than these words. It means, shall we measure lengthways and right across ? or shall we go on the slope and measure askew, in short, shall we take " Square Measure or Skew Measure " ? Let us go back to our original plan. Let us place III on his station at the same distance Midway as ourselves. We meet and part the nearest way, all three going together to the Mid-point. But a new- question arises. How far apart are He and We on the skew ? This is the great question of Trigonometry. It is the question of The Three Places, The Three Ways, The Three Measures. To answer these questions, w T e have to proceed systematically and compare and measure the difference between The Square and The Skew. For this end, place I and II in line, 20 yards asunder ; place III right across 10 yards from Mid-point. We are all three 10 yards from Mid-point. THE GEOMETRY OF THREE WAYS. Ill 63 O V t 4- / \ O * & 10 b > o < S 10 ^ > o i II The first Question of Trigonometry is, How far are we two from him ? To this question there are two answers. The first is, 20 yards on the Square. Second, 14 yards on the Skew. The Second question is, How far are we two from each other ? Answer, 20 yards on the Square. 28 yards on the Skew. There is yet a third answer, which is, "Nobody can exactly tell!" 64 GEOMETRY IN MODERN LIFE. The reason of this particular answer is, that at 20 yards asunder between I and II, and 10 yards off to III on the square from Mid-point, the way from I to III is 14 and on to II is 14 more, making 28 in all. But these numbers in measure have a slight inaccuracy, which we cannot conquer ; and which makes us call them " discords " or " incom- mensurables." But the inaccuracy is so slight as to be of no practical value and easily corrected for use, by adding the decimal fraction, viz. 1 4. 142136 The great object of the Geometry of the Three Ways, is to tell in all cases, the exact measured distance from station to station, in any three ways, for every degree of Skew, and to compare it with the distances on the Square or Eight Across. These measures are treasured in books made at great cost, at Government cost, for the Public Good, and called Trigonometric Tables. By the use of these Tables, Travellers, Sailors, Astronomers, and Geometers of all sorts are saved a life-time of calculation and trouble, by having placed at their disposal the invaluable results of whole lives of many other able men, spent in calculations for our good. THREE-POINT MEASURE. 65 Villi THREE-POINT MEASURE. Three-point Measure grows out of the Geometry of Three Ways, and is one of the parts of Geometric Science of most use in the World of Thought and Work. It is commonly called Trigonometry or Trigo- nometrical Calculation ; and is best known as the Geometry of Navigation, the Geometry of the Globe, and is employed in Britain for the Trigonometrical Survey. It is the basis of our calculations of the places and distances of the stars. My Start-point, your Stand-point, and our Distance Apart, are the basis of all further measures. This we call our Base Line. By means of these we proceed to settle the Place and Distance of all round about us. For this purpose we send another to his station, and ask him to measure as he goes, and mark his F 66 GEOMETRY IN MODERN LIFE. Stand-point. Thus, we choose a Third Station, and he measures a Second Line of Distance, and takes his stand. Thus we stand o Here Yonder III O II o There I Here You There He Yonder. Let us agree to make our Base Line 10, 100, or 1,000 inches long, on paper ; or feet long, on a floor ; or yards long, on the field : or chains long, across the country ; or miles long, in world measure THREE-POINT MEASURE. 67 Let us agree with him that he shall make his Line Right Across from your Station of the same measure. Now comes the important question Can we foretell this Third New Distance from him to me, without measuring ? Answer We can ! How ? By Three-point Measure ! By Antient Geometry ! But why need we calculate, when we have simply to measure it by walking over the ground 1 Because a lake, or sea, or chasm, or precipice, or void, may come between and render your step- ping or measuring inexact or impossible ! Or in war that space might be occupied by the enemy, and you want to take the measure and get round him without his knowing it. Your 3 stations and 2 lines might lie outside a fortress. f 2 68 GEOMETRY IN MODERN LIFE. Returning now to our question, we ask, How far is Station I from Station III ? Answer given by Geometry. If I to II is measured exactly 100 Chains, Base Line. If II to III is measured exactly 100 Chains, Right Across. Then the Third Distance, from 1 to III, on the Skew, Must Measure 141 Chains, and 42 Links. And this the Geometer tells you without ever having made the measure. If you test it by trying you will find his estimate correct. This Three-point Geometry is of the most simple and useful character it implies very few simple elements Two Points in Measured Line. A Third Point, in a Second Measured Line, Right Across. The Third Distance foretold without Measure. THREE-POINT MEASURE. 69 The Geometer's Forecast of the Third Distance. Just as the common Almanac tells you the days of the week, and year, and school- days, and holidays, so the Geometer's guide book tells us the measures of ways for our guidance. Out of the Geometer's book of the Three Ways, I give you the following table and diagrams GEOMETRY IN MODERN LIFE. Geometer's Forecast. Base Line Line Run Skew Line Measured. Right Across. Foretold. Chains of 22 Yards. Chains of 22 Yards. Note The big Figur are Chains, the Small ones are Links. 100 Chains. 10 Chains. 100. 49 100 33 20 13 101. 98 100 33 30 33 104. 40 100 33 40 ,, 107. 70 100 33 50 33 111-80 100 35 60 33 H6. 100 33 70 33 1 22. 06 100 33 80 3 3 128.06 100 33 90 33 134. 53 100 33 100 3 1 141.40 100 35 110 33 148.oo 100 33 120 33 156.20 100 33 130 33 164. 01 100 33 140 > 1 72. 04 100 33 1 50 - i 80. , 7 100 33 160 3 1 188. 67 100 3< 170 3 3 197. 23 100 3) 180 3 205. 91 100 33 1.00 3 3 1 1 - ' 4 -70 100 200 33 '-co THREE-POINT MEASURE. 71 Diagrams of Distances as Forecast by the Table. 100 /.*' /# loo IOC If I 100 Forecast. JOl'M loo 100 ,'1 72 GEOMETRY IN MODERN LIFE. Let us now see how this forecast of figures helps us in life. At sea, under sail, the question arises I want to go due North in the wind's eye. My sailing craft has made good her course N.W. on the starboard tack, 50 knots, and is now on the port tack, N.E., doing other 50 knots. How much due Northing shall I have made out of these 100 knots tacking? Answer 70 knots to the good. This answer is got from the line of figures in the Table 100 100 141. We halve each figure and get 50 50 70 70 On board a ship you propose to have a foremast square up 100 feet high, and 50 feet abaft the stem. How long must the forestay be ? exclusive of the ends to make fast. Answer from the Table Close on 112 feet. And how long must the forestay of the bowsprit be which runs out 50 feet further ? Answer from the Table Close on 142 feet. On land you may ask this question If I go round the corner of the fence 100 paces, and then turn square to the right 150 paces more, how much should 1 save by avoiding the corner, and going aslant through the field ? Answer from the Table 180 feet across. instead of 250 feet round the corner, saving 70 feel of distance. THREE-POINT MEASURE. 73 74 GEOMETRY IN MODERN LIFE. X. MEASURE AND NUMBER. We have already watched the first steps of the Geometer as he leaves his Starting-point, and paces his way to his intended first Station. Arrived there he has measured his first distance. This distance he may call one mile, or two half miles, or four quarters of a mile, or eight eighths of a mile, or eighty chains, or 8,000 links. All these numbers equally represent the one distance from Start to Station. Thus, One measured distance may have Many representative numbers. In this case there are 1, f, i, f, 80, 8,000; also 1760 and 5280 represent the same distance in yard and foot measure. Tims the invention of Standard Measure converts Distances into Numbers. Numbers from that moment become integral parts of Geometry parts that can be kept and studied quite apart but which are MEASURE AND NUMBER. 75 closely allied, and which in modern life render great practical aid, each to the other. One of the most simple and convenient numbers for use in Antient Geometry was the Number 2, and its family. The Number 10 now contests its supremacy in what moderns have widely adopted as the Decimal system. Each has its advantages and disadvantages. TWO. Two and its family have the advantage of pro- ducing a great multitude of Number in Measure, with great simplicity in thought and in work. The consequence of this is that in antient measures we find it generally used. 76 GEOMETRY IN MODERN LIFE. Example. Take i_ A Standard Measure. Cut that in Two. Two. Cut each of these in Two. Four. Cut each of these in Two. Eight. Cut each of these in Two. Sixteen. Cut each of these in Two. Thirty-two. Cut each of these in Two. Sixty- four. MEASURE AND NUMBER. 77 Now "Cutting in Two" is one of the simplest operatioDS. If your measure is a fine thread, or string, or rope, you merely fold it so that one half exactly fits over the other, and the folding point marks the division of Two ; and this you repeat as you choose. This process of cutting in Two may be carried on as far as you choose, and it amounts to a division into more than a thousand minute measures in the tenth operation of cutting. Thus- First cutting makes Second cutting Third cutting Fourth cutting Fifth cutting Sixth cutting Seventh cutting- Eighth cutting Ninth cutting Tenth cutting 2 4 8 16 32 64 128 256 512 1024 Therefore, if you want to divide any measure into very minute parts, in the simplest, quickest, easiest way, the young geometer has no easier way than using the process of repeated division in Two. 78 GEOMETRY IN MODERN LIFE. The antient mariner made a similar use of the Number Two and its family, in Points of the Compass. He first divided the sea all round about him into Two Ways East and West. Next into Two more Ways North and South. MEASURE AND NUMBER. 79 Next, these Four Ways were divided each in two by Four new Ways. These Eight Ways, divided in two, give other Eight Ways, making Sixteen. 80 GEOMETRY IN MODERN LIFE. And each of the Sixteen, parted in two, showed Thirty-Two Ways. Thus the antient mariner settled his Thirty-Two Ways by the same Numbers which gave him his antient Measures of Distance. While we moderns have abandoned the antient measure of 2, 4, 8, 16, and 32, in Measure of Distance, we still adhere to the antient division of ways into 2, 4, 8, 16, and 32, according to the Points of the Compass. My own opinion also is that the antient Knot, or Nautic Mile, used in sea measure, was the length MEASURE AND NUMBER. 81 of B-V of a degree of the earth's girth, which by division into 2, 4, 8, &c, ten times over, became 1,024 fathoms. This differs in the number of fathoms from the modern Admiralty rule, which gives 1,014 English fathoms of two yards as measure of the Sea Mile. This would make a difference of ^ between the length of the Antient and Modern fathom. This example shows clearly the great value of well- chosen numbers. The English Admiralty Fathom and Mile of 1,014, when halved, gives 507. When quartered it gives 2531, or a "broken number;" an eighth gives 126f, another broken number; a sixteenth gives 63f, a number still more broken ; and so on, worse and worse. Whereas, by adopting for Fathom Measure 1,024 to one Nautic Mile, that would still be as true as now, to a man's arm's-length, and 1,024 would be halved 10 times without a single broken number. G 82 GEOMETRY IK MODERN LIFE. Halving a Theoretic Nautic Mile of 1,024 Fathoms. Halvings. Fathoms. Once gives 512 Twice 256 Thrice 128 Four times 64 Five 32 Six 16 Seven 8 Eight 4 Nine ........ 2 Ten 1 Thus Measure and Number, wisely chosen, go together, and help each other. Well chosen Numbers also give aid to clear Thought. These numbers 1 have given as growing out of " Two," are numbers never to be forgotten by thoughtful men who desire to understand nature, creation, and common life. To show that matter and nature in creation "Feel these Numbers," even if they do not understand them, may be gathered from one simple illustration. Sounds composed each of some of those numbers would be all in harmony with each other, and each would sound a perfect octave, to the one below and to the one above it. A string stopped at parts whose length fits these numbers, would give a series of MEASURE AND NUMBER. 83 octaves in j)erfect tune. A series of organ pipes, whose lengths were measured to fit those numbers, would sound a series of octaves all in har- mony. Thus in Nature Order, Measure, and Number rule. As in antient philosophy, so in modern science, Numbers enter into Geometry, in the First Steps of that science. My Stand-point and my Start- point are marked in Geometry by a mark about each, and this mark we commonly call Zero Q or Starting Point. And next, when I have completed One Measure, say a Yard, a Fathom, a Mile, or a Knot, I call that One " Standard" "Unit" "Measure," and I mark it thus .Zero One G Standard Length. ^. Unit; ~~ ^ Starting Measure. Point. In Numbers, in like manner, we have a starting Thought and a starting Mark, which precedes Measure or Number, and which means neither Measure nor Number. It means Nothing Zero a Cypher G 2 84 GEOMETRY IN MODERN LIFE. Ought or Nought. It is the starting place of Number, and is marked thus Zero Ought Nought. In Arithmetic, as in Geometry, there must be a Standard, or Unit, or Constant, or Measure, or One, or Something, in order to give meaning to Numbers, and to give meaning to marks of Numbers. This Standard Mark is called Unity 1, or I, or the Unit One. A Starting Point we call Zero, and a Standard or Unit we call One, for the foundation from which spring together the sciences of measure and number. It is most desirable both for the Student of Geometry, and the Student of Arithmetic, that they should cultivate early the study of numbers, the nature, characteristics, classes, and special uses of each number. Each number has a special nature, a common nature, a pedigree, and a peculiarity. Clear thought and exact work depend mainly on selection of fit Numbers and risht use of each Number. Whether is a number or not is a moot question. In our Decimal Arithmetic it occupies the same place as the other numbers, and fills a similar place, and MEASURE AND NUMBER. 85 sometimes means even much more than they do. Still, it is best to say that " Zero, 0, is no number," and is only the " Starting Point of Number." The same question arises about 1, or I. Is " One " a number ? Some people say " Yes ! it is the First Number, the First of the Numbers. It is No. I ! " But others say, " No ! Two is the smallest Number." One is One, and is not a Number. Perhaps it is wisest to say " One, I, is not itself Number, but is only " The Standard or Measure of Number." If we agree on this mode of speaking, we shall make 2 our first Number. Alone is One. Two together is a Pair, a Couple, a Brace, and may be marked several ways " Two, II. One more than One alone. " One Pair, I Couple, 1 Brace, 2 Uuits." Two alike therefore make a Couple or Pair, in Geometry. In Geometry, if you pace a Chain to meet me, and I pace a Chain to meet you, we call our distance 2 Chains. But we have to make sure beforehand, that our paces are alike. And if we 86 GEOMETRY IN MODERN LIFE. take a string and double it, and cut it in two, we must take care they are alike before we call them 2 Halves. Two therefore, is in exact ways of thought and word, the First Number. It requires exact measure before we admit that the word and mark Two, II, 2, are correctly applied. It applies equally to an increase of I to I making Two Units ; and to a division of I into Two Halves, provided the two parts are duplicates, or alike. One then is our Standard both in Geometry and Arithmetic, and One, and One Alike taken together, give us our First Number in both Sciences, viz., " Two alike without difference," II, 2. THREE. Three is the next Number. We call it a "Perfect Number," and it is sometimes called the " Perfect Number" because it combines the fewest elements with closest ties. Three has a Starting Point and a Stand Point, as No. I has. Three has a eouple of its parts alike, as No. II has. But Three has what the others have not, it has a Centre and Two Sides, it has a middle body and a pair of wings, it is composed out of One and Two together, and therefore includes the qualities of both ! MEASUKE AND NUMBER 87 Three consists of I and II, of I and I and I, and may be represented thus One and One and One, or I and I and I, or I I I or ill or Whether in geometry, in architecture, or in nature, the Number III and its family lead to symmetry, beauty, and perfection. Number Four has little to distinguish it beyond other numbers. It is Two Twos a Pair of Pairs a Couple of Couples. It is merely Two repeated. 88 GEOMETRY IN MODERN LIFE. It is merely the same over again. Four of the same together have little variety, and mere monotony or repetition. FIVE. Number Five has variety with uniformity. First, it has One Unit, and Two Couples, as its elements. In Geometry it has One in a Central Place, and One Pair on either hand. Next, it adds to the Number Three, a repetition of Two. Five consists of I I II I One and Two and other Two. II I I I One and a Pair of Twos. Mill One and Two and Two. .ill. i, Li Two and Three together. MEASURE AND NUMBER. 89 Five consists of the following groups of place ooooo oo oo o oo oo o o o o oo oo By the same process we find that Six is merely a Pair of Threes repeated. That Seven is a Centre, with Six surroundings, or a Central Unit, with Two Threes. That Eight is merely a repetition of Couples, and that Nine is only a repetition of Threes. Thus we gradually come to see Numbers in dif- ferent groups, each with a special character. Know- 90 GEOMETRY IN MODERN LIFE. ledge of the nature of Number is therefore part of the Science of Place, Order, and Measure ; and I have taken the Number Two as a first example of the value of Numbers, and of the special value which belongs to one number, and distinguishes it from others. The first question worth knowing about any number is this Is the number " Even or Odd ? " "Even" means that it belongs to the Number Two. " Odd " means that it disagrees with the Number Two. We thus get the following Classes Even Numbers. 2 4 6 8 10 12 14 16 18 20 Odd Numbers. 1 3 5 7 9 11 13 15 17 19 21 Looking at these we soon see that the " Even " Numbers are each "A Pair of the same." Thus, 4 is a Pair of Twos, is a Couple of Threes, 10 is a Pair of Fives. MEASURE AND NUMBER, 91 Even Numbers are all therefore compounds of a couple of another Number. The ' ' Odd " ones, on the contrary, cannot be parted in Pairs, except by leaving out the Odd One. Thus 3 is a Pair of Ones, with One left out. 5 is a Pair of Twos, with One left out, 7 is a Pair of Threes, with One over. 11 is a Pair of Fives, with One more. Perhaps the best form in which the fitness of Number to place, order and shape may be shewn, is by setting out Places in order. Take Geometer's marks for places, and arrange them in Order and Number I. II. III. IIII. O GO ooo oooo v. VI. ooooo oooooo We soon notice that the Odd One is a middle mark, and that the Even One has no one in the centre. 92 GEOMETRY IN MODERN LIFE. Let us next analyse them by ordering in Couples thus o o o oo oo oo oo oo oo o o oo oo oo oo oo oo oo oo oo oo oo oo oo oo The Odd Numbers are at once detected by the eye from the exceptional place of the Odd One. In this form the Odd One is offensive to the eye, and occupies an exceptional place, and at first sight, perhaps, an inferior place. But when arranged in single lines the Odd One may be set in the most distinguished place, and so have given to it the greatest importance. Thus, among Three, the Centre One is made most important o o MEASURE AND NUMBER. 93 Among Five the Centre One is dominant oo oo Among Seven the Central One is eminent - ooo ooo Among Eleven there may be Two dominant, and One predominant oo oo oo oo The reason of this plainly is, that because Eleven is made up of a Pair of Fives, each Five may have its own dominant centre, and one remains over to dominate the Pair of Side Centres. The Odd Numbers thus admit of an order which is symmetric about a Centre, and the Even Numbers do not. Thus we may range the Odd Numbers in the fol- lowing orderly group 94 GEOMETRY IN MODERN LIFE. O o o o o o o o rf o o o o o o o o o s ooosooo OO0OOOO0 O0OO09OO0 oooooooo 000 ooooooooo O0OO000O0 OO0OOOO0 OOO0OOO s o o o o o O o o o o o o o o o o o p o o o I I P3 MEASURE AND NUMBER. 95 It is plain from this ordering of the Odd Numbers round their Centres, that the Odd Numbers are Aristocrats, and the Even Numbers are Democratic. It will also become plain how the ordering of Atoms, of Matter in Nature, may out of the same matter give strange varieties of groups, according to the wise selection of Number set in order. Out of due ordering of Number in place grows a " Third Order " of numbers, of a quite other nature from Odd or Even numbers. They are commonly called " Square Numbers," and they may be either Odd or Even. Take the Geometer's marks for places, and let us arrange them side by side, but agreeing to limit our- selves to having only as many side by side as we have in one row. We get this Form. OO OO 4 ooo s OO OO OO 2 ooo OO OO O 1 1 oo 4 ooo y OO OO 16 90 GEOMETRY IN MODERN LIFE. OOO OOO' ooooo* OOO OOO ooooo OOO OOO 00000 OOO OOO OOOOO OOO OOO OOOOO OOO OOO 25 36 OOOOOOO 7 OOO0OOO ooooooo OOO0OOO oooo OOO0OOO 49 OOOOOOOO' ooooooo oooooooo oooooooo oooooooo oooooooo oooooooo oooooooo 64 MEASURE AND NUMBER. 97 Thus each Number has a quality which fits it for some special use, and unfits it for some other; and each Number belongs to some family of like Number : and when we know the family to which each belongs, and its place in that family, we can tell its usefulness in Geometry, the part it plays in Nature, and its fitness or unfitness for the uses of common life. In Geometry. If I take a simple element of three-cornered form, and set it out in rows in Odd Numbers, it will grow into larger figures of like form Element b, One. Addition S\ Three. Sum Four. Whole H 98 GEOMETRY IN MODERN LIFE. Addition f\f\K FlvE - Sum Nine, Whole Addition Sum Seven. Sixteen. Whole Addition HSktSJ\ ^ INE - Sum ia Twenty-Five. Whole MEASURE AND NUMBER. 99 In these figures, the first row has 1 the second row has 3 the third row has 5 the fourth row has 7 the fifth row has 9. The whole number of Elements in each is 1, 4, 9, 16, 25. If I take simple elements of Square form, and group them in like manner, by Odd numbers around the first element, I shall have symmetric growth of large out of little, all of like form. ] Take one square add around one corner of j j it three squares Together o these four make one square of four | Take a square of 4' add around one corner I of it five squares 100 GEOMETRY IN MODERN LIFE. Addition Sum Whole h 9 Five. Nine. Addition Seven. Sum 1 1 1 Sixteen. Whole MEASURE AND NUMBER. q u Addition Li Nine. 101 Sum tr Twenty-Five. Whole Even if I next pass to Kound forms, which cannot be built up by numbers of like elements, but which grow by transformation from small to great, by additions of parts unlike the whole, I still find that the same laws of Odd Number rule the growth and the same Square Numbers represent the resulting extent. When we go further into circles, the same reason still holds true A Circle of One, with a belt of 3 rolled round, it becomes doubled in diameter and in size four fold. 102 GEOMETRY IN MODERN LIFE. SEPARATE. Circle Bolt Circle Belt Circle Belt Circle ONE THREE FOUR FIVE NINE SEVEN Belt NINE MEASURE AND NUMBER. 103 JOINED. RESULT. Circle FOUR Circle NINE Circle SIXTEEN Circle TWENTY FIVE 104 GEOMETRY IN MODERN LIFE. When we pass from Forms in Space to Laws of Matter, we find that the same laws of Number rule Moving Mass. The Apple falling from the Tree falls thus : In the 1st quarter second it falls 1 foot 2nd 3 feet 3rd 5 4th 7 5th 9. Thus the speed of the falling apple grows gently but evenly with the time of fall, according to the Odd Numbers, and we can thus sum up the total heights fallen at the end of each period of fall. In One Quarter Second 1 foot is the whole fall. In Two Quarters or Half a Second 1 + 3 feet gives a whole fall of 4 feet. In Three Quarters 1 + 3 + 5 gives 9 feet fall. In Four Quarters 1 + 3 + 5 + 7 gives 16 feet fall. In One and a Quarter Second 1+3 + 5 + 7 + 9 gives 25 feet fall. MEASURE AND NUMBER. 105 And this law of Odd numbers for each quarter, and of Square numbers for the whole time, is the Law of Falling Bodies, equally for Apples from the Tree, Shot from the Gun, Planets Round the Sun. Such Laws of Numbers, Order, Reason, as 1, 3, 5, 7, 9, 11, 13 . . . and 1, 4, 9, 16, 25, 36, 49 pervading Forms, Shapes, Quantities of Things, ruling Geometry, Men ; s Acts, Earth's Phenomena, Orbits of Heaven, lead to the thought, that Number, Measure, Order, Reason, Pervade Equally, the Thinking Mind, Nature of Matter, Forms of Space, Force, Shapes of Things, Motion, throughout the Earth and the Heavens. 10G GEOMETRY IN MODERN LIFE. XI. FAMILIES AND PEDIGREES OF NUMBERS. Between Chaos and Creation, we find this striking difference, that in one all things seem thrown together without purpose, plan or method, while in the other all things are set out systematically in settled place, order and number. Ordered Place means Shape ; Ordered Number means Symmetry. Together they give Symmetric Form. Place without Order means Disorder ; Place without Number means Confusion. Together they give shapeless crowd or Chaos. FAMILIES AND PEDIGREES OF NUMBERS. 107 The first step towards Symmetric Form is giving to each element, Settled Place, giving precise meaning and measure to the thoughts and words Here, There, Yonder. Close, Wide, Afar, Beside, Between, Beyond. The next step towards Symmetric Form is ordering each element into Clear and Exact Relation to each other, as In Line The Same Way. In Lines Parting Ways. In Lines Like Ways. In Groups Round Centres. Thus Order and Rule displace Disorder and Confusion. The third step towards Symmetric Creation is the settlement of a Standard of Unity, or group, or model or measure, out of which all things round about shall grow in proportioned bond or relation, measured by Number. This gives birth to the One, or the Unity, or the Root, or the Base, or the Parent or the ancestor of the rest who follow, surround, or grow out of the Primitive One. In our thoughts of things we have therefore Our Starting Point or Place, which is not a thing nor 108 GEOMETRY IN MODERN LIFE. a measure, nor a number ; though it is the place of one, and though it is often spoken of and thought of as if were a number. It is called Ought, Nought, or Zero. It is marked o, 0> or o. We shall call it in our Geometry, " The Starting Point of Number." The First Number in the common list of numbers is commonly called Number One. But it is not a number in the strict sense of the word, when we take " a number " to mean several or some, or part of many. Nevertheless, we may with due precaution call it the Beginning of Number, the Root of Number, the Foundation of Number, the Unit or Standard by the repetition of which we get, " two," " several," " more " and " many." Number Two Is in reality the First Number, as of use in ex- pressing the connection of one thing with another, FAMILIES AND PEDIGREES OF NUMBERS. 109 or of one thought with another thought, or of one person with another. "Two of the Same" express what we may consider the earliest stage of Genesis of Number. "Two" and "Twin" and "Twain," "A pair" "A Couple" "A Brace," All express this primitive thought of number, or radical beginning of measured thought- It may be called The Elementary Number, and the study of it gives most knowledge most exactly with least pains. But the Number Three is " the typical " and to many the most " perfect " of numbers. It is the first in the whole series of odd numbers, and is only second in the series of families of numbers. The families of numbers, are the various series of numbers, which flow from or grow out of, or are created by some single primitive number, or parent number, or ancestor. 110 GEOMETRY IN MODERN LIFE. Two Has a large family of numbers, all growing up out of it as their root, or descending down from it as their parent. Each of these is the twin family of the parent pair. Family follows family multi- plying by Two, and each family is known by its order, and the number of its descent is called its pedigree. The parent of each family, of pure and unmixed number, is sometimes called the Prime Number, which means the same thing as Princely Pedigree. The following are the most distinguished Prime or Primitive or Princely Numbers + . - I, U, III, V, VII, XI, XIII. It may seem strange at first sight that these numbers should belong to higher rank than the omitted numbers IIII, VI, VIII and Villi; but it will soon appear that those belong to the second or next lower degree of numbers. FAMILIES AND PEDIGREES OF NUMBERS. Ill The Family of The Number Two Has the following series of generations and degrees First Generation II Marked 2 ] Second Generation II and II Marked 2 2 Third Generation ( II II i ii ii Marked 2 3 Fourth Generation II II II II II II II II Marked 2 4 Fifth Generation II II II II II II II II ii II II II II II II II Marked 2 5 . Thus the numbers 2, 4, 8, 16, 32, are the first members of the family, and are technically called "the 1st, 2nd, 3rd, 4th, and 5th Degrees, from the Koot II." 112 GEOMETRY IN MODERN LIFE. The Family of the Number Three Has the following series of generations or degrees First Generation III Marked 3 1 III Second Generation T rr ryr Marked 3 2 III Third Generation IH IH Marked 3 3 III III III III III III 9 9 9 Fourth Generation Marked 3 4 9 9 9 9 9 9 9 9 9 9 9 Fifth Generation 9 9 Marked 3 5 . 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 Thus the Numbers 3, 9, 27, 81, 243, are the first members of the family and are technically called, "the 1st, 2nd, 3rd, 4th and 5th Degrees from the Root TIT." FAMILIES AND PEDIGREES OF NUMBERS. 113 The Family of the Number Five Has the following Members and Degrees First Generation V. Marked 5 1 V, Second Generation v V V V Marked 5 2 (25) 25 25 Third Generation 25 Marked 5 3 (125) 25 25 125 125 Fourth Generation 125 Marked 5 4 (625) 125 125 625 625 Fifth Generation 625 Marked 5 5 (3125). 625 625 Thus the Numbers, 5, 25, 125, 625, 3125, are the First Numbers of the Family, and are technically called " the 1st, 2nd, 3rd, 4th and 5th Degrees from the Root V." 114 GEOMETRY IN MODERN LIFE. The Family of the Number Seven Has the following Members and Degrees First Generation Marked 7 1 VII Second Generation Marked 7 2 (49) VII VII VII VII VII VII VII Third Generation Marked 7 3 (343) 49 49 49 49 49 49 49 Fourth Generation Marked 7 4 (2401) 343 343 343 343 343 343 343 Fifth Generation Marked T (16807). 2401 2401 2401 2401 2401 2401 2401 Thus the Numbers 7, 49, 343, 2401, 16807, are the First Numbers of the Family, and are technically called "the 1st, 2nd, 3rd, 4th and 5th Degrees from the Root VII." FAMILIES AND PEDIGREES OF NUMBERS. 115 The Family of the Number Eleven. First Generation Marked ll 1 XI Second Generation Marked ll 2 (121) XI XI XI XI XI XI XI XI XI XI XI Third Generation Marked ll 3 (1331) 121 121 121 121 121 121 121 121 121 121 121 Fourth Generation Marked ll 4 (14641) 1331 1331 1331 1331 1331 1331 1331 1331 1331 1331 1331 Fifth Generation- Marked ll 5 (161051) 14641 14641 14641 14641 14641 14641 14641 14641 14641 14641 14641 i 2 116 GEOMETRY IN MODERN LIFE. 0000)0 ooooo ooppo ooooo " bp bp bo bp bo t bo bo bo bo QQftQP QQQPQ CO P3 W 09 s D ^ >< GO J H a >-J t <5 Ch dn w ti a o H no O H C O &c P^ pa Ed ps< o H > w i i J fe CQ < H H CO PR w a c 8 (XJ CO CO i I CO fc> C5 CO I 1 1^ ^ -* o o CO -* CO (M CO > m o o >o cq CI cq C ^ ^ ^ -3 OlCO-^iO CD t^ CO C5 ^H o CO r^ GO CTi o O o o i i CO co CD "<* 1 1 1 1 r^ GO f^ -=* i i o r^ CO iO -+ Ol I 1 i^ *# C^ C5 -*+ i t en ^ r^ r^ i i r < C3 o CO cq CO iO CM Ci CO 11 Jt^ "* Tj< o o o iO CO co Jt^ CO ^ CO 11 Ol co o r 1 oo 1^ CO o o cq -* CO CO Cq CO CD Ol UO . ' S oi co ^ >o co i^ go cr. C5 CM O CI CO CO o m O o o OT cq OT cq - i CO C5 cq CO T* cq co co co Tf CO r^ i i o CO o cq CO 1 1 C5 CI o 2^ FAMILIES AND PEDIGREES OF NUMBERS. 117 When we have made ourselves familiar with these Princely Families of Numbers, so as to single them out readily from among crowds of common numbers, we have the great advantage of knowing all about them with perfect certainty of accuracy and with least trouble in calculation. We can also see beforehand the many consequences to which combinations of them may lead. Thus if you look at the family of II, and ask " what number would be the result if I multiply 16 by 64 ? " the family table of II at once leads you to the answer. You see there that 16 is the 4th Degree and that 64 is the 6th Degree the 4th Degree with the 6th Degree, make the 10th Degree. The 10th Degree in the Table of II is " 1024," and that is the answer to your question. In like manner, the numbers 81 and 729, belong to the family Table III. 81 is the 4th Degree, 729 is the 6th Degree combined they yield the 10th Degree whence we learn that "the product of 81 by 729 yields" the number found in the Table of III in the 10th Degree, we find there the result already foreshown, " 59049." But the reverse process of calculation is in common Arithmetic much more tedious. If I wished to know " how often I could take 625 out of 15625 V I seek in the Table of Degrees, and in the Family of V I find 625 in the 4th Degree 118 GEOMETRY IN MODERN LIFE. and 15265 in the 6th Degree. There are 2 Degrees of difference. If I look to the 2nd Degree I find 25 is the 2nd Degree of the Family V. "25 times " is the answer to my question. This relationship flows all through these Families of Princely Numbers, so that a man who has mastered them becomes nearly an intuitive omnis- cient calculator. Such men spend their lives in making calculations for us, and giving us the note-books of their Life's Work. Napier, Babbage, De Morgan, and many such men, have stored up all their work in millions of figures and multitudes of pages. What you have to learn at College, is the skill to understand and use their work, so as in after life to spare your labour by utilising theirs. To do work wisely by using only the right numbers, you must know thoroughly the nature of the numbers you put your trust in, for many men have made the greatest blunders in Life's Work by putting trust in the wrong number. I have seen the Water Works of a great City ruined by an Engineer who was not master of the right figures taking the wronoj ones, and when the works were ready (as he counted) the water came in and the works broke down ! He had chosen the wrong familv ! FAMILIES AND PEDIGREES OE NUMBERS. 119 If you will look down the columns of the Families of the Prime Numbers, you will see some curious characteristics of each, which may be of great use to you in life, and may often keep you from being deceived. Look down the family of III and ask yourself if you see any likeness, visible to the eye, on the face of all the members of that family ? because if you see any one number wanting that mark, that number is a blunder, and is not one of the family. The mark seen on the face of the Family III is this mark The figures each member of the family consists of, all make "nine." The Second Degree is 9 ; the Third Degree is 27 ; and these two figures 2 and 7 together make 9. The Fourth Degree is 81, and these two figures 8 and 1 together make 9. The Fifth Degree is 243 and these three figures 2, 3 and 4, together make 9, and so on all the figures in each member of this family when added together, make nine, or two nines, or three nines or more nines, and any others show error. On the face of the Family V is this mark, that the two last figures in each member are " two and five." The Second Degree is 25 ; the Third Degree is 125 ; the Fourth Degree is 625, and the Fifth 3125, all ending in 25. The Family VII end successively in 9, 3, 1, 7, 9, 3, 1, 7, &c. &c. All the Family of XI end in 1 . Thus the Third Degree 120 GEOMETRY IN MODERN LIFE. is 1331 and the Sixth Degree is 1771561, quite unlike excepting this ending in 1. Besides these characteristics of each Princely Family of Numbers, there are a multitude of others which grow up in our minds as we become more intimate with each of them and more familiar with the uses to which they may conduct us. But the most important results of these Numbers of High Pedigree flow from their powerful influence over other Numbers, which mingle with the vast crowd of Vulgar Numbers and as it were give organisation of Rank and Degree to large classes of Ordinary Numbers. Each Family of Prime Numbers, may enter into alliance with other Families of Prime Numbers, and so give rise to New Families of Aristocratic Pedigree but of Mixed Family. Thus the Family of (2 2 ) Two in the 2nd Degree may unite with the Family of (3 2 ) Three in the 2nd Degree and the product of the two will be a mixed breed of Number (2 2 , 3 2 ) or (2, 3) 2 and the resulting Number 36, becomes a Number of great practical Value in all Matters which concern equally Matters compounded of Twos and Threes. We say therefore of the Number 3G, that it conies of the united Families Two and Three in the Second Degree ; and hence we at once know many of its qualities, and can predict many of their consequences. FAMILIES AND PEDIGREES OF NUMBERS. 121 We may next go a step onward and in a following generation of Two, we may introduce a family con- nection with Five. Take the Family of Two in the Third Degree (2 3 ) already connected with (3 2 ) in family bond (36) and let a .new member be taken from the Family Five. The product of the Family 2 3 and 3 2 when united with 5 1 , or the First Degree of the Family Five, gives us the Number 360. The great value of this Number has been well known and much used during many centuries of time in many nations. It represents nearly, but not exactly, the number of days in a year. But it is so useful that we all divide the Circle of the Globe, and the Heavens, and our own Little Circles, into 360 Little Degrees, or small parts of a Circle. Some people have tried to find a better Number than 360, but they have failed. The Number 352 is a favourite number of mine ; and if I had lived at the time wdien the Family 360 was first installed into Governing Power over the territory of the Circle, I might perhaps have fought a battle in favour of 352 ; but it is too late ! 360 dominates the Circle for all time ! And there are good reasons in favour of 360. If [ want to halve it, it yields an unbroken number, 180. If I want to quarter it, it gives me 90, and if f want eight equal parts it gives me 45, being 122 GEOMETRY IN MODERN LIFE. three unbroken numbers. But if I asked it to go further, it would break down, and a sixteenth part of 360 would be the very vulgar fraction or broken number 22^. But in compensation for this defect, 360 allows me to part it in three parts of 120 each, into six parts of 60 each, into twelve parts of 30 each, and into twenty-four parts of 15 each all free of broken numbers or vulgar fractions. I can also divide a circle into five parts of 72 each, or ten parts of 36 each, or twenty parts of 18 each, or forty parts of 9 each. All without breaking a number or producing a vulgar fraction. Now all this convenience, a skilled man can fore- see and foretell, by mere inspection of the Pedigree of the Number 360. Its Pedigree being (2 3 , 3 2 , 5 1 ) he foretells that you can divide by 2 three times over, by 3 twice over, by 5 once ; and by 2 with 3, by 3 with 5, by 5 with 2. Thus orderly unbroken groups of Division and Subdivision grow out of the wise choice for Daily Universal Use, of a number having a varied and mixed but Primary Pedigree of the Princely Numbers, II, III, and V, in the Degrees [2 :! , 3 2 , 5 1 ]. It thus becomes plain, how much knowledge grows out of the Pedigree of Numbers and how much FAMILIES AND PEDIGREES OF NUMBERS. 123 use comes from the wise selection of fitting numbers for each given purpose in life. It is therefore worth while to study the Pedigree of all Common Numbers, in order to judge which to choose and which to reject. The following Table of Pedigrees of the First Sixty-Four Ordinary Numbers has therefore been prepared in order to assist in the study of the characteristics of each and their con- nections with each other. It may be worth notice that the Ordinary Numbers in their usual succession form the First Eow on the Left without Distinction. Along the top are the Five Prime Numbers of Highest Distinction, the Roots of the Largest Families, and below each Head of the Family are ranged the successive Members of the Family marked each by his respective order or degree. On a line with each member of a Family is the title and Degree of any Second Family with which he is allied and of a Third or a Fourth Family with whom he is allied. On the extreme Right of this Table will be found a Row of Numbers of No Pedigree. They may be called, if we like, Ancestors themselves, as they 124 GEOMETRY IN MODERN LIFE. do produce families " few and far between " : but they do not come in any way from any of the Princely Families, although they may form connections with them farther down. We sometimes call them " Prime," but not Princely Numbers. Availing ourselves of the information in this Table let us see what we can gather from it, about the common Numbers with which we are familiar. At the top of Ordinary Number stands ? Zero is no Number it is Nought. But it marks a Place and is the Starting Point of All Number. I? is not a "Number" it is not "some" or "any" or "many." But it is the Standard of Number the Measure of Number ; it forms the Standard Unit by the repetition of which Numbers are made. Two therefore is our First Number, II. One and another, of the same make Two. FAMILIES AND PEDIGREES OF NUMBERS. 125 Two therefore implies a " Pair," " Measured/' " Alike." It is the first result of Measure, the first step in Number it is the Ancestor of the First Family of Number ; and its product is a multitude of Even Numbers, into all of which the Family of Two enters in a lower or higher degree. All Numbers which have any alliance with Two, will find a portion of their pedigree in the column of the Table headed II. III. Number Three takes its place next to Two, at the Head of the Family of 3 ; and all numbers allied to it, find their representative in the column of the Table headed III. Four is a most important valuable Number and in some ways is a perfect number but it is not the Head of a Family. It is the second member of the Family of Two and under the head of Two it takes rank in the Second Degree as 2 2 . V. Five is the head of a Family next in rank after Three. There are few r er members of the Family of 126 GEOMETRY IN MODERN LIFE. Five in the Table, than of Two or Three. But there are many numbers of high value which have their Pedigree in the Family of Five. Thus 10 is formed by the union of 2 1 with 5 1 . Again, 20 or a " Score " is formed by the union of 2 2 with 5 1 , and 100 is derived from the union of 2 2 with 5 2 . Five is the Patriarch of most important Families in modern calculation, although the Family of Two had higher prestige in Olden Time. <;. Six has little distinction among numbers, except as half-a-dozen. It is the simple union of Two in the first degree with 3 in the same. VIT. Seven is a Prime Number, next in importance after Five, and the head of a family of which still fewer members will be found in the Table. Nevertheless all its progeny have interesting and valuable characteristics. Is a distinguished and most valuable number, and is the first which attains the distinction of the Third Degree. It is the Third Degree of the Family Two, 2''. FAMILIES AND PEDIGREES OF NUMBERS. 127 9. Nine is a most distinguished and interesting number. It has all the good qualities of the parent number Three : it is 3 2 , and is sometimes considered as having all the qualities of Three intensified. Three threes is a sort of perfection in the Second Degree. 10. Ten is the Type or Standard or Model Number of Modern Measure and Modern Calculation. The whole French Nation have become slaves to its rule, and we are fast following. The temptation to give Number Ten the sole absolute rule of all Measure and all Number is so great, that few of modern Nations have been able to resist it. Logically it seems perfect. In fact it is a painful tyranny to which Englishmen have a natural antipathy, and against the compulsory and universal adoption of which in English Rule Measure, Money, and Thought, we continue to rebel. Perhaps the true wisdom in such cases is a compromise. Let us take the Number Ten at what it is good for ; but accept it thus far and no farther. It is good for our intercourse with most 128 GEOMETRY IN MODERN LIFE. continental nations ; it is the basis of our own common arithmetic. But our own measures of Distance have Eleven as their unit ; our own measures of Weight have Seven as their unit ; our own measures of Value have Twelve and Twenty as their units, combining the primitive numbers Two, Three, and Five. Let us preserve our own measures for our own ways of thought but let us learn the Decimal System of Weights, Measures and Money, just as we learn foreign tongues, for convenience of foreign intercourse and foreign travel. Ten therefore must hold its high place as the Standard of Decimal Counting and Decimal Measure although it is not a Prime Number but a combination of Five with Two, or 2 1 with 5 1 . It results from the union of Two First Families of Number in the First Degree. It is also useful to remember that 10 being 10 1 or Ten in the First Degree 100 is 10 2 or Ten in the Second Degree. 1000 is 10 3 or Ten in the Third Degree. 10000 is 10 4 or Ten in the Fourth Degree 1,000,000 is 10 6 or a million. 1,000,000,000 is 10 or a thousand millions. 1,000,000,000,000 10 12 or a million millions. FAMILIES AND PEDIGREES OF NUMBERS. 129 But it may also be useful to remember that 2 10 exceeds 1,000. 2 20 exceeds 1,000,000. 2 30 exceeds 1,000,000,000. 2 40 exceeds 1,000,000,000,000. XL Eleven, which follows Ten in our ordinary numbers, is the parent of a large family of interesting Numbers, by union with other Families. It is marked by the repetition of the other numbers on the face of the product. Thus 22, 33, 44, 55, 66, 77, 88, and 99, are merely the product of Eleven united with 2, 3, 4, 5, &c. Eleven thus leaves its distinguishing mark on all the early members of its family connections. 12. Twelve, though not a primitive number, is yet one of the most useful and convenient of early Numbers. It is the union in One Number, of the early numbers 2, 3, 4, and 6. Twelve consists of- a Pair of Sixes, of Three Fours, of Four Threes, and of Six Couples. This makes it the most con- venient in the handling of Common Numbers in daily Merchandize. K 130 GEOMETRY IN MODERN LIFE. XIII or 13. Is a Transition Number, from the Highest Pedigree to Numbers without Pedigree. The fault of Thirteen is, that its family are few, and their relations to other Numbers very rare. Compared with the family connections of its next neighbour Twelve, it really has little or no connection, and is little and rarely seen in union with other families. It may be seen two or three times in our Table in connection with 2 and 3. 14. Fourteen has no particular quality except as the double of Seven or 2 with 7. 15. Fifteen is the first result of the union of Five with Three, or 3 1 with 5 1 . 16. Sixteen is a distinguished, important and useful number of High Pedigree. It is Two raised to the Fourth Degree. It comprehends in its pedigree the lower numbers of Eight, Four and Two or 2 1 , 2 2 , 2 3 . Its practical convenience is that you can halve it, FAMILIES AND PEDIGREES OF NUMBERS. 131 then quarter it, then split each quarter in two, and that again in two ; and do this without breaking the number or splitting it up into fragments or making vulgar fractions of it, which is so often disagreeable. Sixteen is a most convenient number and is found in the Family Table II and is marked 2 4 . 17. Is a Number of no Pedigree and very little use. Only a few scattered numbers come of it. Still it is a Prime Number. Eighteen is a convenient and useful number. It is half-way between 12 and 24, or between One Dozen and Two Dozen, and it is the half of Three Dozen. It is the outcome of Two with Three, or 2 1 with 3 2 and its family is intimately allied with all theirs. 19. Nineteen has no Pedigree, little connection, very rare family and very little use, excepting to fill up the void between the very useful numbers Eighteen and Twenty. It is a Prime Number. k 2 132 GEOMETRY IN MODERN LIFE. FAMILY PEDIGREE OF THE FIRST SIXTY-FOUR ORDINARY NUMBERS. O H H U o W H i i w m i i P O W H THE FIVE FIRST PRINCELY NUMBERS OR PRIMES. II III V VII XI 2 ... 2 1 3 4 ... 2 2 5 6 ... 2 1 ... 7 8 ... 2 3 9 3* 10 2i ... 11 II 1 12 ... 22 ... 13 13 14 ... 2^ ... 15 3 1 ... 5 1 16 2* 17 17 18 2i ... 19 19 20 2 2 ... 21 22 2 1 IP 23 23 24 ... 2 3 ... 3i 25 5' 26 ... 21 13 27 3' 28 ... 2 2 V 29 29 30 ... 21 ... 3 1 ... 51 31 31 32 V a 5 GC Q O o Q fcg Q f o w 7 T Ao i 1 d r i +-> -M +J +- fl wj o O 0> o Ci O) .&> ,v o 5yD ^ ^-1 <4-H -* I t+_ M-l t+=l J^ V DPh CJ CO r 1 00 -* oo 00 CO p > GO 00 <4_, O O T I co CO o X cq 05 CO X & -d 03 CO go X CO X ** X CO CD CO as X O oq 3 x CO CO a. a> .a * CC of SP d > o rt 00 GO ce oo cq _, d ,-h o Oco C7i [V, -* SYMMETRY, HARMONY, AND MELODY. 155 Now each of these groups is melodious with the others, because each group of 8, 9, and 10 is in near alliance with the next, and because 7, 8, 9, and 10 is a like series of steps in Dumber and sound. And these same notes have harmonic relations to each other, by the union in the same measure of time, of like numbers of groups ; and by the fact that when sounded together the tones are harmonious in the exact degree in which numbers belonging to one family bring about agreement. Thus we see by the eye that E must harmonise with B because their family numbers are 2 3 5 1 and 2 2 3 1 5 1 Groups of 5 waves being given out in one case in pairs, and in the other in triples, per second, or in perfect harmony. In like manner we may foresee that D must harmonise with A, because their family numbers are 2 2 3 2 and 2 1 3 s 156 GEOMETRY IN MODERN LIFE. Groups of nine waves being given out in both cases, in the one 4 groups fitting in with 6 groups in the other, in each second, a perfect harmony of 3 and 2. All these tonic relations of sound, are therefore, the embodiment in matter, and the development into symmetric wave motion, of the harmonic numbers given in our table on page 133, from which the fol- lowing: has been taken. II II 32 . 2 5 36 2 2 . 3 2 40 2 3 42 2 . 3 48 2 4 3 54 2 . 3 3 60 . 2 2 . . 3 64 . 2 6 VII XI c D E 7 F G A B C Thus I have tried to show you that numbers of high family pedigree, when they go out into the world of material phenomena, rule the ways in which matter works, that they express and explain the phenomena of agreement and disagreement in the air waves that carry sound into our ears, that they are felt by our nature and accepted by our minds, as agreeable and disagreeable even when we are not familiar with their nature ; and that education in the family nature and individual pedigree of number enables us to give a rational explanation of the SYMMETRY, HARMONY, AND MELODY. 157 phenomena of concord and discord, and may materially aid us in gaining mastery over the mysteries of melodious succession and harmonious symphony. But I should fail in rewarding you for the pains of this study, if I did not point out to you the many gains it gives to wider knowledge of modern science, and higher skill in Art and Life. Harmonic and melodious number rule many of the marvellous w T orks of God, as well as the occupations of man. God has told the atmosphere in which we live, to carry far and wide, sweet sounds, but to refuse to carry discordant noise ; or rather to favour the transit of sweet sounds and to hinder that of harsh ones. When you are far away from sounding instruments and from the voice of song, you will notice that its effect on your ear and mind is much sweeter, than when you were near. Why is this ? It is because it is a law of creation, that Sounds in Harmony shall be carried by waves that assist each other, while Discords are dropped out and left behind. It might be difficult to explain this discriminative faculty of the carrier wave of sound, but it is so. Not merely the carrier wave has this natural bias against transporting disagreeable sound ; but Tlw 158 GEOMETRY IN MODERN LIFE. Matters which cause sounds, and send forth the sound waves to us, have an innate antipathy to discords. The Eolian Harp is a simple set of stretched strings, left to itself in an air-current. The breath of the wind blowing on the strings produces in the ear of the listener wild melody and exquisite harmony : why not discord ? We only know that each string, struck by the wind, produces only the tones which belong to the harmonic series, which we have selected from our table of family pedigree. It refuses to sound any other. All the numbers in our last column are left out. Hence inanimate nature loves Order, Measure, and Number as we do. Perhaps it is the mind of God which moves both it and us. If I were to settle the right proportions for an ordinary drawing room, in which the music of song was to be well heard and which should at the same time be seemly to the eye, I should give to it the proportions of harmonic sound. Say 30 feet for the length. Take 12 feet for the height. And 18 feet for the width. Thus we have, Length 5 times 6. Breadth 3 times 6. Reiefht '1 times (>. SYMMETRY, HARMONY, AND MELODY. 159 Therefore the families 2, 3, and 5, the prime numbers of perfect harmony, are all represented here, and are united by the common bond of 6, which is itself the outcome of 2 with 3. The physical consequence of this will be that all three dimensions of the room will agree in favouring these harmonic sounds and in suppressing discords. The sound waves will also travel three ways ; along the room, across the room, and up and down. The waves of sound in these three sets, will form groups of six, of which groups, every 2, 3, 5, will exactly time each with the other, and so each will help all, and there will be no hindrance to continuance and perfection of harmony. A room of 29 feet, by 17 feet by 13 feet, would be nearly the same size, and to the eye nearly the same proportion, but to the air and the sound wave and the voice of the singer and the ear of the listener, would be impracticable and intolerable. Every room has a key tone and a harmony or discord of its own, and a speaker or singer is heard ill or well and gives voice with ease or pain, according as his voice and the room's dimensions agree or disagree. o In a beautiful work of the sculptor, like proportions rule the human form. Harmonic Form has like number with Harmonic Sound. " The works of God are made in Order, Measure, and Number." 160 GEOMETRY IN MODERN LIFE. Take a well-proportioned man, say of six feet. The following are his measures and numbers Inches. Height 72 Outstretched arms 72 Arms' length from centre of body . . 36 Length of hand 8 Length of face 8 Length of head and neck from collar bone to crown 16 Breadth from shoulder joint to shoulder joint 16 Length from elbow to finger point. . 18 Length from shoulder joint to hip joint Length from hip joint to knee joint . Length from knee joint to ankle joint. Length of foot 10 Length from shoulder joint to elbow joint 10 Height of ankle joint above heel . . 2 Yards- 2 2 1 Now all these numbers are our harmonic numbers 2, 3, and 5 and none other. 2 3 with 3 2 make 8x9 2' J with 3' make 4x0 2' with 3 2 make 2 x 9 2 1 2- x 2- SYMMETRY, HARMONY, AND MELODY. 161 2 1 with 5 1 makes 2x5 10 inches 2 3 makes 8 2 1 is 2 Hence all grow out of the Prime Families of Number and Harmony 2, 3, 5. The total height is Head and neck 16 Body 18 Upper leg 18 Lower leg 18 Heel 2 72 In like manner, when we go into the vegetable kingdom, we see everywhere developments of form and number, symmetric and harmonious. The following are two examples of symmetric form growing from the Koots II and V in conformity with the Family Degrees of these two prime numbers> already given in pages 162 and 163. M 162 GEOMETRY IN MODERN LIFE. Example of Symmetric Form growing from the Number II. (See page 111.) SYMMETRY, HARMONY, AND MELODY. 163 ^* Example of Symmetric Form growing from the Number V. (See page 113.) m 2 164 GEOMETRY IN MODERN LIFE. XIII. SIGHT, LIGHT, SHAPE, AND SHADOW. Shapes of things as they are in themselves, shapes of things as they seem to my eye, shapes of things as they are in my mind, may be and often are strangely different. One of the arts of life is to shape things out of matter to shape lovely forms out of lumps of clay, to hew marble columns out of limestone rocks, to shape graceful ships out of forest trees, to rear comely mansions out of common bricks, to carve groups of men out of blocks of stone, to paint a lovely scene of forest, mountain, lake, and stream, to draw on paper an interesting object so as to show it exactly as we saw it, to draw on paper the shape of some new thing with precision, so that another shall see it in the mind's eye exactly as it will be seen by them after it has come to exist ; these are some of the practical works of common life, and all these are merely Geometry. SIGHT, LIGHT, SHAPE, AND SHADOW. 165 Light is one of the most useful instruments of human life, and one of the most useful tools of the Geometer. Light shows shape, Light shows distance, Light throws shadow, Light is the food of life, and is also the food of the eye and the mind. To the Geometer, Light going straight from far to near, marks out straight lines in space ; striking on masses of matter, it marks out shape by shadow and shade ; coming into his eye it tells him place and direction, and enables him to measure size, tell distance, and mark out shape. Light therefore deserves the study of the young Geometer. It shines out of a light-sending body in straight lines. It strikes on dark bodies and makes them shine by its own shine, and makes them seem to shine by a light of their own. Shining light makes other bodies throw their shine off from them- selves also in straight lines, and these straight lines of light entering our eyes make us see the bodies which sent them to us ; and when we look at a near flower or a distant star, the coloured light of the one and the clear light of the other enable us to see them along the line of light which came to us, in the near distance or far away. Hence we see straight because light comes to us straight from the form seen. It is by the Geometry of lines of Light that an astronomer tells the place of a fixed star or of a 166 GEOMETRY IN MODERN LIFE. moving planet ; that he foretells the aspect of Saturn's rings ; that he tells from Jupiter's satellites the hours in the heavens, in the same way as we do the hours of the clock from the place of its hands; that he foresees the moment when the moon will enter the shadow of the earth, which shadow will be cast off by straight lines of light coming from the sun and stopping on the earth, while others escape past the earth and carry light all around. On the earth's surface, it is the lines of light coming from the lighthouse that enable the mariner to keep clear of rocks and sands, and steer his ship safe home to her destined port. It is by "taking sights " of sun, and moon, and satellites and stars that the sailor is able to tell his latitude and longitude and know his exact place in the wide ocean, when there is nought in sight but sky and sea, and so Geometry of lines of Light and Sight becomes essential to the art of modern navigation, and is part of a seaman's skill and sailor's education. In like manner, on land, it is by a series of optical instruments, called telescopes, sights, theodolites, reflecting circles, sextants, quad- rants, altitude and azimuth circles, and such like geometric tools for measure by lines of light, that the Geometer performs all the operations of place- fixing, time-marking, and way-finding through the heavens and over land and sea. A single example will show how much a skilful SIGHT, LIGHT, SHAPE, AND SHADOW. 167 Geometer may learn out of a single sight of one phenomenon of light in the heavens. A skilled yachtsman, an Etonian, was very lately making researches in matters of science in his own yacht, which he navigates himself, and had gone far to the north in somewhat hazy weather, and wanted much to know his " whereabouts." Luckily, near midnight the weather was clear ; and just then and there our yachtsman saw the sun, not in the act of setting, but in the act of just touching the sea and then rising up again, as it does only in summer " very far north." This single sight carefully noted, told him his yacht's exact place on our round world. The sight was easy and simple, the calcula- tion somewhat long and complex, and I have great pleasure in presenting it to you as a sample of one use of an Etonian's Geometry. 168 GEOMETRY IN MODERN LIFE. OUR ETONIAN'S OBSERVATION AND CALCULATION OF HIS YACHT'S PLACE IN THE NORTH SEA. 1877, July 23, Midnight ; in Longitude 21 55' E. The observed Altitude of the Sun's upper limb (the lower limb being obscured by cloud) when on the Meridian below the Pole was 1 T 40". Index Error, Nil ; Height of Observer's Eye, 10 ft. The Latitude was found as follows : h. m. s. o ' Astronomical apparent time at J July 23 J2 Q Q L(mg> 21 5g Long, in time E 1 27 40 ,, 4 Astronomical apparent time at Greenwich 23 10 32 20 Sun's Declination at apparent ) July 23 N. 20 1 19*5- Noon at Greenwich \ Change in 24 hours . Greenwich Time h. m. s. Change in 10 32 20 . Sun's Declination as above Reduced Declination . Sun's Codeclination or Polar distance Observed Altitude Dip 10 feet Refraction .... Parallax .... Sun's Semidiameter . True Altitude of Sun's Centre . Sun's Codeclination or Polar distance Latitude .... 24 19 48 467 90 70 4 11 N. 1 7 40 - 3 10 1 4 30 - 23 58 40 32 + 09 40 41 - 15 47 24 54 + 70 4 11 70 29 5 N h. m. s. 1 27 40 12 32*8 Log. 2817 h. m. s. 10 32 20 Log. 3574 .-05 30-5 Log. 6391 20 1 19*5 19 55 49- SIGHT, LIGHT, SHAPE, AND SHADOW. 169 Thus we learn that lines of light are the Geometer's guides in the use of his instruments and tools, for the finding of places, the measuring of distances, the drawing of shapes and ways on paper, and the laying out of lines of railway, lines of road, boundaries of estates, courses of ships, shores of seas, outlines of lakes, and paths of planets. How to show on flat paper the shapes of things you see round about you, some far off, some near at hand ; how to show them truly as they are, and also as they seem to your sight; to make true plans, drawings, outlines, shades, shadows, and pictures with absolute truth and perfect exactness that is a hard problem and requires a Master- Geometer. And to a sound Geometer, the problem is de- lightful and beautifully simple. First, you have to fix your own stand-point, which we call the place of the seer. Second, you have to settle the way the thing lies from yourself, or the way you must look to see what you want ; that we call the line of sight. Third you must know how far off each thing lies from yourself. Next, how far it lies to the right or the left from your line of sight. 170 GEOMETRY IN MODERN LIFE. Thus you learn, or settle the place of each thing you mean to place in your plan or picture. This you must do before you begin, and it is called plotting out or preparing or placing your objects. This placing each thing in its right place is mere plain Geometry. You Take your stand-point. Settle your line of sight. Mark off distances from your stand-point. Mark off places to the right. Mark off places to the left. Having marked off places and distances as they are in fact, you have next to mark them off as they seem. 1 Now the fundamental principle about placing things as they seem instead of as they are is this Things on the right of the seer, seem at less and less distance from the line of sight, or the mid-line, in exact proportion as they are further off from the seer. Thus a nearer thing seems more to the right than a further off thing which is exactly the same distance off on the right from mid-line. Therefore, if a row of trees are all equi-distant from a mid-line, and each at distances of 1, 2, 4, 8, 16, 32, chains SIGHT, LIGHT, SHAPE, AND SHADOW. 171 from me ; their distances from the mid-line will seem to me 1, i, t, 1, rV of the true distance. What happens in distance of place to the eye happens also in seeing size. Each tree of the same size at distances from me of 1, 2, 4, 8, and 16 chains, will seem to me successively as of the diminishing sizes 1, h t, I, tV. Thus the arrangement of place, the settling of distance, and the measure of size, are all quite different to the eye from what they are in fact ; and if a picture or a plan is to show truly to the eye what the eye has seen or is to see, the Geometer and the Artist must draw them on paper, not as they are but as they should seem and Geometry alone can do that true and exact. What I have said of place to the right and of place to the left of the sight-seer is equally true of place above his own level or below his own level. Heights above his eye and his line of sight grow less and less on the plan, and seem less and less to the eye, as they are further and further from the seer, and exactly in the same proportions of 1 I, t, I, tf, heights, to 1, 2, 4, 8, 16 distances. And what is true of heights above the eye is equally true of depths below the eye. The right placing of all things to be seen in a plan or picture is a mere carrying out of the same system 172 GEOMETRY IN MODERN LIEE. of Geometric stand-point, measured way off, and distance square across, which we have already studied among the First Steps of the Geometer ; and is equally applied to right and left distance and to distance up or down ; and this law of seeming diminu- tion of size and distance, with increasing way off as measured from the seer, is the addition wanted to carry it into use. One of the most interesting and one of the most common uses of the Geometer's art is the laying down on a sheet of paper, or on a flat board, or on a sheet of canvas stretched out flat, the Shape, Outline, Form, or Appearance, of The things he sees. This art of showing things in shape as they seem to our eyes, by lines and shades and lights and shadows, is a modern art of great interest and every day use. It is commonly called " The Art of Projection." " Descriptive Geometry." " The Science of Perspective." In plain English it is How to show the Shapes you see. SIGHT, LIGHT, SHAPE, AND SHADOW. 173 How to show to another on a flat sheet, the shapes of things you have seen, so truly that he shall see them, or seem to see them, just as truly as you did see them in reality. That is the high art of the modern painter ; it is the humbler art of the modern draughtsman and engraver ; it is an art which must be founded upon a profound and thorough knowledge of the laws of light and sight. The first Geometric law of light is that light comes straight from light-giving bodies or sources of light, and enters into or strikes on all other bodies round about them. The second Geometric law is that light comes straight from visible forms to the seer's eye. Next we have to take into account The shape of the body in reality. Its attitude as we see it. Its seeming shape in that attitude. Its seeming size in distance. Its exact place from line of sight. Take one example of Simplest shape, Say A Common Square Box. 174 GEOMETRY IN MODERN LIFE. The Geometer's technical term for this simple form is a "rectangular parallelopipedon," but the words "square box " are equally plain. A common square box, if set straight in line with the seer's eye, on the same level, will seem a common square flat front, and he will only see that face of the box, and no other. Now the box has six faces Top and Bottom. Front and Back. Two ends Right and Left. Let us distinguish these six faces by colour : Top, Yellow. Front, Red. Bottom, Blue. Back, Black. Right end, Orange. Left end, Green. When the box stands on our level straight in front, we see a square Red shape only. If raised higher, we see the Red front and a Blue bottom joined on. If set lower, we see the Red front and the Yellow top together. SIGHT, LIGHT, SHAPE, AND SHADOW. 175 If set on the level to our right, we see the Red front with a Green end on its left. If set on our level to our left, we see the Red front with an Orange end on its right. Then follow four more attitudes : The box may stand Below us on the Right. Below us on the Left. Above us on the Right. Above us on the Left. In four cases we see four sights 1. Yellow, Red, and Green. 2. Yellow, Red, and Orange. 3. Red, Blue, and Green. 4. Red, Blue, and Orange. In these four last not only are the faces changed in colour, they are all changed in visible shape. They were all square, now all seem skew. There is still another series of semblances, of the same box shape, according to attitude. Fancy the same box shape suspended in the air ; by a string from one corner, it 176 GEOMETRY IN MODERN LIFE. would present to the eye a new series of pictures as it was spun round the axis or string. Now in that box you have only to fancy there is contained a statue or a work of art of any kind, and it is plain that in each of these positions and attitudes of the box the statue within takes a like attitude. And if you fancy the box made of glass, the statue would be visible to the seer's eye, but each sight of the statue would be a different picture. This serves to show you the chief difficulty of the painter, planner, and designer. He has 1st, to know exactly the things as they are ; 2nd, to know exactly how they will seem. This art of showing shapes on the flat as they are seen in fact, or as they are intended to seem when seen, requires the exercise of many faculties and much precise knowledge. But of all these faculties the most essential is the art of the Geometer. That the great old painters were great Geometers, their life and works indisputably show. Eubens, Michael Angelo, and Leonardo da Vinci, were accom- plished Geometers. When I was investigating this question in the Low Countries, I had a curious illustration of the union of Geometric w^ith Artistic craft. An ancient town was hefeditary owner of extensive lands. The town corporation held a meeting SIGHT, LIGHT, SHAPE, AND SHADOW. 177 at which, a councillor proposed that an exact Geo- metric Survey of the town-lands should be made. It was thought " worth while/' and it was agreed that the survey should be paid for at so much per acre- The question who should be the Geometer, or lands surveyor, was decided by one councillor assuring the members that there was only one good Geometer in the town, and he named their greatest painter, one whose fame still stands high. The painter accepted the order. He carefully measured all the lands of the corporation, including streams, trees, fences, gates, farm -buildings and dwelling-houses. I had the great pleasure of examining his work, then some hundred years old, and carefully preserved in the town-hall. He not merely laid down his plans exactly on parchment, but also gave a plan, painted in oil, and representing all the lands, trees, and buildings, in one single view, in exquisite Geometric perspective, showing everything true as on a picture. This Geometric projection of land-surveying is really a beautiful oil painting, and I should never have fancied it other than a mere landscape, had I not found this curious history in the well-kept record of proceedings of the old town corporation. The truthfulness of all this painter's pictures was quite explained to me by his mastery of the mystery of representing visible form by exact Geometric method. 178 GEOMETRY IN MODERN LIFE. XIV. GEOMETRY, MATTER, FORCE, AND MOTION. The machinery of mechanical forces and motions which constitute the main elements and powers employed in the Engines, Engineering, Arts, Manu- factures and Industries of Modern Life, are matters mainly of modern civilization and scarcely at all of tradition. Our great mechanical inventions have come to us mainly from the great discoveries of the laws of the universe of matter by Galileo, Huyghens, Kepler, and Newton. The discoveries of modern science and the development of modern invention have gone hand in hand ; and have created the present marvellous navigation of the ocean and the travelling over continents and around seas ; which give to us little human beings a power of going everywhere in small portions of our short lives, as well as being nearly omnipresent in mind and thought by electric telegraph ; while our steam-engines are doing the work of thousands of horses and millions of men. GEOMETRY, MATTER, FORCE, AND MOTION. 179 All this has grown out of the modern discoveries of the laws of force, mass, and motion. Happily for us, these modern laws were found to be at one with the antient laws of Geometry. It is quite conceivable that Geometry of void space might have had one set of rules, and that the massive, moving matter of the universe might have had new laws of its own, quite inconsistent with the laws laid down by the mere Geometer. All this is conceivable, and has been conceived : and has led many men to spend their lives in inventions and discoveries which seemed mathematically perfect and which are materially impossible. Modern discoveries tested by experience have taught us that masses of matter, still or moving, starting from rest, stopping from motion, move as accurately, stop as exactly, change their speeds and alter their ways with as perfect precision as if they were celestial beings moving to music of the spheres, and mapping out a Geometer s Forecast of their ways and distance. A planet, a cricket-ball, and a swing, all describe Geometric paths in precise measure, time, and distance, as foretold in the Geometer's Forecast. Matter moving free, goes on straight and even. That is the first law of Matter Nature. Matter in motion changes not, it neither goes faster nor slower ; it neither turns to right nor left nor changes N 2 180 GEOMETRY IN MODERN LIFE. upwards nor down. Ever onward, changeless. That is the law and nature of Dead Matter. But hindered matter takes heed of hindrance, and yields. Helped matter accepts help and turns it to use. One moving mass lends help to another moving mass, directs its course, turns it back, or increases its speed. But all this it does by settled way and measured number. In all its ways matter follows the settled rules of the Antient Geometry. Matter moving free goes on straight. Matter moving goes in measured distance. Matter moving free keeps true time. Matter yields by measured way to force. Matter turns aside by measured degree yielding to measured force. Matter goes faster yielding by measure to measured force. Matter goes slower yielding by measure to measured force. GEOMETRY, MATTER, FORCE, AND MOTION. 181 How force turns moving matter aside ? is an interesting, instructive, useful question. You row a boat across a lake, going straight. You move the water out of your way, that takes force. But you next row across a stream already going straight another way. What happens % Which way do you go ? Not the way you row ! Where do you land ? Not where you direct your boat ! The law of the matter is this Each force does its own work as if the other did not exist ! If you row 4 miles an hour your way, you do your 4 miles just the same in the stream as in the still. While you do your 4 miles, the stream does its 3 miles in the hour. The double result is this 1. You have gone your 4 miles with neither more nor less effort than in the still. 182 GEOMETRY IN MODERN LIFE. 2. The stream has taken you its 3 miles without other effort than if you had lain still. 3. But the joint' result is A new way. On which third way The boat and load have gone 5 miles ; While you were going 4 and the stream going 3. The result then is A new way and a new speed. This resulting way and speed arising from boat and stream combined is identical with the pure Geometer's Forecast of Three Points and Three Ways, as given in Tables and Diagrams on pages 70, 71. The general law of combined motions, forces, and masses is, that each does its own work its own way, and that any two forces and motions do make one third force and motion exactly as the Three Ways of the Geometer foretell. Thus taking the Diagrams on page 71, which are here repeated, we find GEOMETRY, MATTER, FORCE, AND MOTION. 183 Diagrams of Distances as Forecast by the Table. 100 /(? 100 .J Forecast. IQI'M loo ^tyf--"' 100 184 GEOMETRY IN MODERN LIFE. Thus in the first figure, if 200 tons were a force acting upright, 100 tons a second force acting horizon- tally, the result of the two would be a strain of 223*60 tons on the slope. If altered to the form of the next figure, there would only be a strain of 180 tons on the upright, and 205*91 on the slope. If in the third figure, the length of two roof rafters were represented by 100, and of the tie-beam by the sloping side, we should conclude that each strain of 100 lbs. on a rafter would produce a strain of 141*41 lbs. on the tie. From the fourth figure we may learn that if a ship were moved by tide along 100 fathoms, while moving by wind 150 fathoms as shown, the result of the two would move that ship 180 fathoms along the third side, and this third side will show the true course of the ship. The two last figures show that a weight of 101*98 tons may be pulled up one slope by a force of 20 tons, while a weight of 111*80 tons drawn up the other slope will require a force of 50 tons. It is with the heavenly bodies as it is with earth masses. A comet may be rushing past the earth at a thousand miles an hour. The earth attracts the comet as it does the apple. It pulls it towards the earth's centre. The Geometer knows GEOMETRY, MATTER, FORCE, AND MOTION. 185 the comet's speed. He knows the speed the earth can give to the comet in a different course. He makes out his diagram of the three ways, and this third way tells him the new way and the new speed of the comet. Thus Geometry w T ith laws of matter mark out a new and formerly unknown w r ay of this comet through the distant heavens. Thus out of two ways of force and speed grows a third way which is the result of their joint action. But in this third way our moving mass might have a new influence brought on it. This new force with its new w T ay the Geometer would treat just as before and out of the third way combined with a fourth he would get a fifth. Therefore we now know that all calculation of force, mass, way, and speed, is merely an application of Geometry to the grand law revealed to us by experience of nature ; that the laws of Way, Measure, and Number have been laid upon the matter universe so as to be quite intelligible to those students who know the ways of the Great Geometer. The science of mass, motion, and force is an application of the principles of the Geometer to the laws of matter by measures of length, distance, and direction ; which represent space, speed, and way. 186 GEOMETRY IN MODERN LIFE. When two motions go one way, we add their speeds, and double the distance done. When two motions are contrary, we deduct the less from the greater, the difference being the resulting motion. When two motions go different ways, each does its own distance ; we take the common starting-point and the two separate arriving-points of the two independent motions, and we join all three. The first two lines measure the two independent ways, and the third line measures the third way resulting from the two. And this process of the three ways will not only resolve two forces into a third, but will find a fourth force growing out of three, and a fifth force growing out of four ; and will truly represent and measure any number of forces continually changing the result of any number of forces, successive or simultaneous. Thus Geometry makes plain to our minds the laws of matter, motion, and speed. But this same Geo- metric solution of the problems of moving bodies, by a diagram of three ivays, gives us the solution of a multitude of other questions which are not questions of motion, but questions of stedfastness. We want a locomotive engine and a train to move over a bridge, but we do not want the bridge to move with them, GEOMETRY, MATTER, FORCE, AND MOTION. 187 and therefore the bridge- maker has to learn how to make his bridge stand stedfast, and not to suffer itself to be induced to participate in the motions of the train. This requires skill in the art of securing rest, and preventing motion. Sound Geometers do this, but clever men who are not skilled, build bridges which cannot resist temptation to move, and so are sent into the abyss of chaos. The ancient Roman viaducts still standing are noble examples of Geometric skill, and it is interesting to know that they were designed and built by Greek Geometers for Roman masters. The art of bridge building, the skill of setting work stedfast, consists mainly in knowing how to stop two forces by one, and how to oppose one destructive force by two others, which do not seem directly opposed to it. A train on a viaduct weighs down the top of an arch, a prop direct from below might keep the bridge from falling ; but that is not the purpose of the bridge, which has to keep the train in the air, by support taken from two distant piers, one before and the other behind the train. How to hold up the train, with no support beneath, by stedfast support brought from two distant places, is the problem to be met. We have here three points. We have here three ways. The Geometer draws three lines from point to point. He groups 188 GEOMETRY IN MODERN LIFE. them together, and measures their length. One length he takes to measure the weight of the train say for each ton of train an inch of length. He next measures the two remaining sides of his diagram, when he finds that every ton weight of train produces two tons, or three tons, or one ton and a half of strain on the material of the bridge. Experience tells him if his bridge can stand this strain or not, and if so, for how long? Modern science tells us that trains take some of the life out of a bridge every time they cross it with a heavy load. The builder of a modern viaduct is either therefore a good Geometer, or he is good for nothing, and his bridges give way because he does not know the Geometric method of preventing motion, because he does not know that one force prevents two, and two forces prevent one, according as three points, three distances, and three ways, are ill chosen or well and so his work is foolish or wise, or wasteful, useful, dangerous or enduring. All youths who wish to become distinguished designers, builders, engineers, architects, or sculptors, must first become good Geometers. ENDING ENDLESS. 189 XV. ENDING ENDLESS. What I have shown you of Geometry is only the first flight of a few steps upwards towards that great temple of knowledge, where you may find stored for you by the antient Geometers, and completed by the modern philosophers, the great system of divine thought and human knowledge, which constitutes the laws of space and matter, of shape and substance, of force and motion ; and by means of which you may, in after life, foresee distant events, provide for difficult undertakings, calculate ways and means, foretell dis- tances, courses, and time, and do all your work in the material world in order, measure, and number. But I have merely shown you the threshold of that vast system of truth, revealed to us in the works of the Great Geometer. I have only tried to assist you in selecting a few first steps of solid ground, on which you could firmly set foot, and so placed in line that you should see clearly which way they lead you 190 GEOMETRY IN MODERN LTFE. through the difficulties of the unknown, towards those great heights of thought and those wide ex- panses of knowledge which lie beyond. It is not for me to conduct you onward through this journey of school study, and of life's work. For that I leave you in the w r orthy hands of your able masters, with whom I am proud, in this small degree, to co-operate in directing your ways towards the acquisition of knowledge, wisdom, and usefulness. I have only a few concluding words to say, for the purpose of giving you some idea of that Geometry of which hitherto I have said nothing. Of the Geometry of Place and Distance, and of Points and Lines, I have tried to give you some precise thoughts and exact expressions, and practical uses. But of the whole theory of curve lines [ have scarcely said one word, though I have said some things which are meant to lead you that way, and prepare you for these after studies. Of Circles I have said nothing, except where 1 showed you how they grew by additions, following the laws of Odd Numbers ; and in like manner, as Squares and Triangles grow, though in different fashion. But I must now tell you that when men come to make long journeys inland, over wide con- tinents, and when men make voyages across wide oceans, those ways that we call " straight," are not so. The straight ways of every day life become ENDING ENDLESS. 191 great circles, when we wander wide over the ocean, and the Geometer who surveys the globe, and the navigator who sails the ocean, have to be well aware that a line which seems straight is no longer so, and that what seems a straight course is only Part of a Geeat Circle of the Globe. When you go further on in Geometry you will find that the able seaman has to master the science of " Spherical Trigonometry," instead of Plane Trigo- nometry, and that instead of finding the shortest way in the world is to go straight, he finds that the art of navigation teaches him great circle sailing as the art of " slow, sure, and quick." "Great circle sailing" round the world teaches us many truths, and also requires of us much skill. When we turn to the right or the left, as we must often do, to avoid an island, a rock, or a shoal, or when driven aside by stream or storm, we have to find our way back into our circle again, and verify our place and distance. This tests the adept's skill in Spheric Geometry. Also, it teaches us much we on land have small chance to notice. As we go on sailing in our great circle round the earth, we find the sea "rounding" under our ship. Every mile of distance forward on one course, the sea rounds downwards under our feet ! The measure of this rounding is 8 inches. 192 ' GEOMETRY IN MODERN LIFE. Having found that 8 inches is the measure of the earth's rounding, we may take this as our standard unit of deviation from the straight, when we go round the earth on a "great circle." And when we have taken this measure of 8, and called it our standard I or unit, we can find other larger devia- tions by the nature of the circle and our old law of Odd Numbers. Thus The earth bends round downwards in the Together. First Mile I. Unit. Second III. 4 Third V. 9 Fourth VII. 16 Fifth Villi. 25 Sixth XL 36 Summing up any of these we choose, we find that in 3 miles we have nine measures of deviation, or 9 X units of 8 inches. Making 9 X 8, or 72 inches, or 6 feet. Whence we learn that in 3 miles over sea, on a great circle, we go downwards 6 feet. In like manner, by summing any other descents, we find that in 4 miles we have gone down 16 units ENDING ENDLESS. 193 of 8 inches or 10 feet, in 5 miles 25 units, or lGf feet, and so on. These deviations from the straight on the circles of the globe, lead us on to the knowledge of all the characters of the circle. But the circle is not the only curve in nature, although the most common in our ways of working and thinking. Knowledge of the characteristics of the circle leads us forward to many other ways of Deviation from the straight. After you have learned the Geometry of great circle, circle sailing, and the Geometry of the globe, com- monly called Spherical Trigonometry, you will then merely have been introduced to the first member of The Great Family of Curve Lines. " The crow Hies straight ! " " The arrow goes straight ! " These are common sayings, but when you go beyond common opinion, and get a little nearer the truth, you find that the arrow does not go straight, that like the ship it drops downwards as it goes. When you study the path of the arrow closely, you find that it droops, so as to form a curve that " looks like " a great circle, or a bit of one. o 194 GEOMETRY IN MODERN LIFE. At first it seems as though the arrow followed exactly the great circle of the earth, in the rate of drooping by gravity as it goes, only with a different unit, differing according to the different speeds with which the arrow leaves the bow ; but with wider experience we find it not so. They are like, but not alike. The arrow from the bow droops by a New path of descent, which forms A new curve line, commonly called "The Parabola." This parabolic path deviates from the straight path and forms a new path, and leads to new principles of Geometry, gives new modes of calculation, and teaches us new methods of work. The parabolic curve shows us the paths of The arrow from^the bow. The bullet from the pistol. The bolt from the rifle. The shell from the cannon. The comet from far away. ENDING ENDLESS. 195 The next curve which we meet in nature, and of which Geometry "tells the tale," is The Elliptic Curve. It is the path of a planet round the sun, of our earth through space, of the moon round about us, and of Jupiter's satellites round about him. The Geometer of the heavens has therefore to master the elliptic curves, and to make the elliptic calculations belonging to the paths of each, and all of the heavenly bodies, before he can foresee and foretell for us all the facts that will appear in the heavens, as they will appear to the eyes of any sailor in any part of the ocean, for years to come. All this he does for you and me, and stores up for us for years before they are wanted, in a plain book, for the guidance of all sailors along their great circles round the globe, and this you buy in a common sea- man's shop for a few shillings, and it is called the Nautical Almanack ! The next curve we have to study is called The Hyperbola. It is a wilder and stranger curve than the circle, ellipse, or parabola, and was thought to be " the prodigal son " of the family, from his eccentricity and 196 GEOMETRY IN MODERN LIFE. his endless wanderings from which it seemed as though he would never return. At last the hyperbolic path was found amenable to rule and order, and made of use in the work of modern life. The Hyperbolic Curve tells us the true theory of the rebellions among atoms of water in steam boilers, and how they strive against the unwise intrusion of undue heat into the wrong place, or at the wrong time, and when the right principles of boiler-making and of boiler-heating are not carried out or wrongly timed ; then the atoms following the nature of the Hyperbola, break all bounds, burst their iron bonds, tear in pieces all about them who would control or cross them, and disperse and dis- appear into infinite space ! These are merely the first few families of curve lines ; after which there follow generations and families in multitudes of order and degree ; deeply interesting in nature, and highly useful in application ; like the Families of Numbers of which you already know the degrees, the appli- cations, and the use. And now in leaving off I have to make an end of a real pleasure : but I feel deeply that I have reached a conclusion in which nothing is concluded. Geometry has beginnings. It has no bounds. It is endless, for its last steps arc the knowledge of the endless and the boundless. ENDING ENDLESS. 197 The highest Geometry is The Geometry of the infinite and The Geometry of the infinitesimal. But even there the human geometer's mind is in some degree permitted to compass divine thought, and he finds at every step of the progress of man's thought towards the analysis of the infinitely great and towards the integration of the infinitesimal, that his thought of limits and measures becomes clearer and clearer as his view stretches wider and farther, and also goes narrower and deeper. He finds further that as his mind comprehends more and more the marvels of infinite space, and penetrates more and more into the mysteries of the infinitely minute : by so much the more does he become able to appreciate the marvels of the creations, of earth and heaven, and the more does he find his own mind filled with the thoughts that pervade all the works of the Great Geometer. 1 0EOZ 6 MEfAZ TEHMETPHZ LONDON : R (LAY, SONS, AND TAYLOR, BREAD STREET I1II.L, E C. b f -3 * \\03fy M"DP A^nili THE LIBRARY UNIVERSITY OF CALIFORNIA Santa Barbara THIS BOOK IS DIE ON THE LAST DATE STAMPED BELOW. I00M II 86 Series 9482