MATHEMATICAL MEMORIES: NEWTON'S BINOMIAL THEOREM


The spider's web is a glorious mathematical problem. I should

enjoy working it out in all its details, were I not afraid of

wearying the reader's attention. Perhaps I have even gone too far

in the little that I have said, in which case I owe him some

compensation: 'Would you like me,' I will ask him, 'would you like

me to tell you how I acquired sufficient algebra to master the

logarithmic systems and how I became a
urveyor of Spiders' webs?

Would you? It will give us a rest from natural history.'



I seem to catch a sign of acquiescence. The story of my village

school, visited by the chicks and the porkers, has been received

with some indulgence; why should not my harsh school of solitude

possess its interest as well? Let us try to describe it. And who

knows? Perhaps, in doing so, I shall revive the courage of some

other poor derelict hungering after knowledge.



I was denied the privilege of learning with a master. I should be

wrong to complain. Solitary study has its advantages: it does not

cast you in the official mould; it leaves you all your originality.

Wild fruit, when it ripens, has a different taste from hothouse

produce: it leaves on a discriminating palate a bittersweet flavor

whose virtue is all the greater for the contrast. Yes, if it were

in my power, I would start afresh, face to face with my only

counselor, the book itself, not always a very lucid one; I would

gladly resume my lonely watches, my struggles with the darkness

whence, at last, a glimmer appears as I continue to explore it; I

should retraverse the irksome stages of yore, stimulated by the one

desire that has never failed me, the desire of learning and of

afterwards bestowing my mite of knowledge on others.



When I left the normal school, my stock of mathematics was of the

scantiest. How to extract a square root, how to calculate and

prove the surface of a sphere: these represented to me the

culminating points of the subject. Those terrible logarithms, when

I happened to open a table of them, made my head swim, with their

columns of figures; actual fright, not unmixed with respect,

overwhelmed me on the very threshold of that arithmetical cave. Of

algebra I had no knowledge whatever. I had heard the name; and the

syllables represented to my poor brain the whole whirling legion of

the abstruse.



Besides, I felt no inclination to decipher the alarming

hieroglyphics. They made one of those indigestible dishes which we

confidently extol without touching them. I greatly preferred a

fine line of Virgil, whom I was now beginning to understand; and I

should have been surprised indeed had any one told me that, for

long years to come, I should be an enthusiastic student of the

formidable science. Good fortune procured me my first lesson in

algebra, a lesson given and not received, of course.



A young man of about my own age came to me and asked me to teach

him algebra. He was preparing for his examination as a civil

engineer; and he came to me because, ingenuous youth that he was,

he took me for a well of learning. The guileless applicant was

very far out in his reckoning.



His request gave me a shock of surprise, which was forthwith

repressed on reflection: 'I give algebra lessons? ' said I to

myself. 'It would be madness: I don't know anything about the

subject!'



And I left it at that for a moment or two, thinking hard, drawn now

this way, now that with indecision: 'Shall I accept? Shall I

refuse? ' continued the inner voice.



Pooh, let's accept! An heroic method of learning to swim is to leap

boldly into the sea. Let us hurl ourselves head first into the

algebraical gulf; and perhaps the imminent danger of drowning will

call forth efforts capable of bringing me to land. I know nothing

of what he wants. It makes no difference: let's go ahead and

plunge into the mystery. I shall learn by teaching.



It was a fine courage that drove me full tilt into a province which

I had not yet thought of entering. My twenty-year-old confidence

was an incomparable lever.



'Very well,' I replied. 'Come the day after tomorrow, at five, and

we'll begin.'



This twenty-four hours' delay concealed a plan. It secured me the

respite of a day, the blessed Thursday, which would give me time to

collect my forces.



Thursday comes. The sky is gray and cold. In this horrid weather,

a grate well filled with coke has its charms. Let's warm ourselves

and think.



Well, my boy, you've landed yourself in a nice predicament! How

will you manage tomorrow? With a book, plodding all through the

night, if necessary, you might scrape up something resembling a

lesson, just enough to fill the dread hour more or less. Then you

could see about the next: sufficient for the day is the evil

thereof. But you haven't the book. And it's no use running out to

the bookshop. Algebraical treatises are not current wares. You'll

have to send for one, which will take a fortnight at least. And

I've promised for tomorrow, for tomorrow certain! Another argument

and one that admits of no reply: funds are low; my last pecuniary

resources lie in the corner of a drawer. I count the money: it

amounts to twelve sous, which is not enough.



Must I cry off? Rather not! One resource suggests itself: a highly

improper one, I admit, not far removed indeed from larceny. O

quiet paths of algebra, you are my excuse for this venial sin! Let

me confess the temporary embezzlement.



Life at my college is more or less cloistered. In return for a

modest payment, most of us masters are lodged in the building; and

we take our meals at the principal's table. The science master,

who is the big gun of the staff and lives in the town, has

nevertheless, like ourselves, his own two cells, in addition to a

balcony, or leads, where the chemical preparations give forth their

suffocating gases in the open air. For this reason, he finds it

more convenient to hold his class here during the greater part of

the year. The boys come to these rooms in winter, in front of a

grate stuffed full of coke, like mine, and there find a blackboard,

a pneumatic trough, a mantelpiece covered with glass receivers,

panoplies of bent tubes on the walls, and, lastly, a certain

cupboard in which I remember seeing a row of books, the oracles

consulted by the master in the course of his lessons.



'Among those books,' said I to myself, 'there is sure to be one on

algebra. To ask the owner for the loan of it does not appeal to

me. My amiable colleague would receive me superciliously and laugh

at my ambitious aims. I am sure he would refuse my request.'



The future was to show that my distrust was justified. Narrow

mindedness and petty jealousy prevail everywhere alike.



I decide to help myself to this book, which I should never get by

asking. This is the half-holiday. The science master will not put

in an appearance today; and the key of my room is practically the

same as his. I go, with eyes and ears on the alert. My key does

not quite fit; it sticks a little, then goes in; and an extra

effort makes it turn in the lock. The door opens. I inspect the

cupboard and find that it does contain an algebra book, one of the

big, fat books which men used to write in those days, a book nearly

half a foot thick. My legs give way beneath me. You poor specimen

of a housebreaker, suppose you were caught at it! However, all goes

well. Quick, let's lock the door again and go back to our own

quarters with the pilfered volume.



And now we are together, O mysterious tome, whose Arab name

breathes a strange mustiness of occult lore and claims kindred with

the sciences of almagest and alchemy. What will you show me? Let

us turn the leaves at random. Before fixing one's eyes on a

definite point in the landscape, it is well to take a summary view

of the whole. Page follows swiftly upon page, telling me nothing.

A chapter catches my attention in the middle of the volume; it is

headed, Newton's Binomial Theorem.



The title allures me. What can a binomial theorem be, especially

one whose author is Newton, the great English mathematician who

weighed the worlds? What has the mechanism of the sky to do with

this? Let us read and seek for enlightenment. With my elbows on

the table and my thumbs behind my ears, I concentrate all my

attention.



I am seized with astonishment, for I understand! There are a

certain number of letters, general symbols which are grouped in all

manner of ways, taking their places here, there and elsewhere by

turns; there are, as the text tells me, arrangements, permutations

and combinations. Pen in hand, I arrange, permute and combine. It

is a very diverting exercise, upon my word, a game in which the

test of the written result confirms the anticipations of logic and

supplements the shortcomings of one's thinking apparatus.



'It will be plain sailing,' said I to myself, 'if algebra is no

more difficult than this.'



I was to recover from the illusion later, when the binomial

theorem, that light, crisp biscuit, was followed by heavier and

less digestible fare. But, for the moment, I had no foretaste of

the future difficulties, of the pitfall in which one becomes more

and more entangled, the longer one persists in struggling. What a

delightful afternoon that was, before my grate, amid my

permutations and combinations! By the evening, I had nearly

mastered my subject. When the bell rang, at seven, to summon us to

the common meal at the principal's table, I went downstairs puffed

up with the joys of the newly initiated neophyte. I was escorted

on my way by a, b and c, intertwined in cunning garlands.



Next day, my pupil is there. Blackboard and chalk, everything is

ready. Not quite so ready is the master. I bravely broach my

binomial theorem. My hearer becomes interested in the combinations

of letters. Not for a moment does he suspect that I am putting the

cart before the horse and beginning where we ought to have

finished. I relieve the dryness of my explanations with a few

little problems, so many halts at which the mind takes breath

awhile and gathers strength for fresh flights.



We try together. Discreetly, so as to leave him the merit of the

discovery, I shed a little light on the path. The solution is

found. My pupil triumphs; so do I, but silently, in my inner

consciousness, which says:



'You understand, because you succeed in making another understand.'



The hour passed quickly and very pleasantly for both of us. My

young man was contented when he left me; and I no less so, for I

perceived a new and original way of learning things.



The ingenious and easy arrangement of the binomial gave me time to

tackle my algebra book from the proper commencement. In three or

four days, I had rubbed up my weapons. There was nothing to be

said about addition and subtraction: they were so simple as to

force themselves upon one at first sight. Multiplication spoilt

things. There was a certain rule of signs which declared that

minus multiplied by minus made plus. How I toiled over that

wretched paradox! It would seem that the book did not explain this

subject clearly, or rather employed too abstract a method. I read,

reread and meditated in vain: the obscure text retained all its

obscurity. That is the drawback of books in general: they tell you

what is printed in them and nothing more. If you fail to

understand, they never advise you, never suggest an attempt along

another road which might lead you to the light. The merest word

would sometimes be enough to put you on the right track; and that

word the books, hidebound in a regulation phraseology, never give

you.



How greatly preferable is the oral lesson! It goes forward, goes

back, starts afresh, walks around the obstacle and varies the

methods of attack until, at long last, light is shed upon the

darkness. This incomparable beacon of the master's word was what I

lacked; and I went under, without hope of succor, in that

treacherous pool of the rule of signs.



My pupil was bound to suffer the effects. After an attempt at an

explanation in which I made the most of the few gleams that reached

me I asked him:



'Do you understand? '



It was a futile question, but useful for gaining time. Myself not

understanding, I was convinced beforehand that he did not

understand either.



'No,' he replied, accusing himself, perhaps, in his simple mind, of

possessing a brain incapable of taking in those transcendental

verities.



'Let us try another method.'



And I start again this way and that way and yet another way. My

pupil's eyes serve as my thermometer and tell me of the progress of

my efforts. A blink of satisfaction announces my success. I have

struck home, I have found the joint in the armor. The product of

minus multiplied by minus delivers its mysteries to us.



And thus we continued our studies: he, the passive receiver, taking

in the ideas acquired without effort; I, the fierce pioneer,

blasting my rock, the book, with the aid of much sitting up at

night, to extract the diamond, truth. Another and no less arduous

task fell to my share: I had to cut and polish the recondite gem,

to strip it of its ruggedness and present it to my companion's

intelligence under a less forbidding aspect. This diamond cutter's

work, which admitted a little light into the precious stone, was

the favorite occupation of my leisure; and I owe a great deal to

it.



The ultimate result was that my pupil passed his examination. As

for the book borrowed by stealth, I restored it to the shelves and

replaced it by another, which, this time, belonged to me.



At my normal school, I had learnt a little elementary geometry

under a master. From the first few lessons onwards, I rather

enjoyed the subject. I divined in it a guide for one's reasoning

faculties through the thickets of the imagination; I caught a

glimpse of a search after truth that did not involve too much

stumbling on the way, because each step forward rests solidly upon

the step already taken; I suspected geometry to be what it

preeminently is: a school of intellectual fencing.



The truth demonstrated and its application matter little to me;

what rouses my enthusiasm is the process that sets the truth before

us. We start from a brilliantly lighted spot and gradually get

deeper and deeper in the darkness, which, in its turn, becomes

self-illuminated by kindling new lights for a higher ascent. This

progressive march of the known toward the unknown, this

conscientious lantern lighting what follows by the rays of what

comes before: that was my real business.



Geometry was to teach me the logical progression of thought; it was

to tell me how the difficulties are broken up into sections which,

elucidated consecutively, together form a lever capable of moving

the block that resists any direct efforts; lastly, it showed me how

order is engendered, order, the base of clarity. If it has ever

fallen to my lot to write a page or two which the reader has run

over without excessive fatigue, I owe it, in great part, to

geometry, that wonderful teacher of the art of directing one's

thought. True, it does not bestow imagination, a delicate flower

blossoming none knows how and unable to thrive on every soil; but

it arranges what is confused, thins out the dense, calms the

tumultuous, filters the muddy and gives lucidity, a superior

product to all the tropes of rhetoric.



Yes, as a toiler with the pen, I owe much to it. Wherefore my

thoughts readily turn back to those bright hours of my novitiate,

when, retiring to a corner of the garden in recreation time, with a

bit of paper on my knees and a stump of pencil in my fingers, I

used to practice deducing this or that property correctly from an

assemblage of straight lines. The others amused themselves all

around me; I found my delight in the frustum of a pyramid. Perhaps

I should have done better to strengthen the muscles of my thighs by

jumping and leaping, to increase the suppleness of my loins with

gymnastic contortions. I have known some contortionists who have

prospered beyond the thinker.



See me then entering the lists as an instructor of youth, fairly

well acquainted with the elements of geometry. In case of need, I

could handle the land surveyor's stake and chain. There my views

ended. To cube the trunk of a tree, to gauge a cask, to measure

the distance of an inaccessible point appeared to me the highest

pitch to which geometrical knowledge could hope to soar. Were

there loftier flights? I did not even suspect it, when an

unexpected glimpse showed me the puny dimensions of the little

corner which I had cleared in the measureless domain.



At that time, the college in which, two years before, I had made my

first appearance as a teacher, had just halved the size of its

classes and largely increased its staff. The newcomers all lived

in the building, like myself, and we had our meals in common at the

principal's table. We formed a hive where, in our leisure time,

some of us, in our respective cells, worked up the honey of algebra

and geometry, history and physics, Greek and Latin most of all,

sometimes with a view to the class above, sometimes and oftener

with a view to acquiring a degree. The university titles lacked

variety. All my colleagues were bachelors of letters, but nothing

more. They must, if possible, arm themselves a little better to

make their way in the world. We all worked hard and steadily. I

was the youngest of the industrious community and no less eager

than the rest to increase my modest equipment.



Visits between the different rooms were frequent. We would come to

consult one another about a difficulty, or simply to pass the time

of day. I had as a neighbor, in the next cell to mine, a retired

quartermaster who, weary of barrack life, had taken refuge in

education. When in charge of the books of his company he had

become more or less familiar with figures; and it became his

ambition to take a mathematical degree. His cerebrum appears to

have hardened while he was with his regiment. According to my dear

colleagues, those amiable retailers of the misfortunes of others,

he had already twice been plucked. Stubbornly, he returned to his

books and exercises, refusing to be daunted by two reverses.



It was not that he was allured by the beauties of mathematics, far

from it; but the step to which he aspired favored his plans. He

hoped to have his own boarders and dispense butter and vegetables

to lucrative purpose. The lover of study for its own sake and the

persistent trapper hunting a diploma as he would something to put

in his mouth were not made to understand or to see much of each

other. Chance, however, brought us together.



I had often surprised our friend sitting in the evening, by the

light of a candle, with his elbows on the table and his head

between his hands, meditating at great length in front of a big

exercise book crammed with cabalistic signs. From time to time,

when an idea came to him, he would take his pen and hastily put

down a line of writing wherein letters, large and small, were

grouped without any grammatical sense. The letters x and y often

recurred, intermingled with figures. Every row ended with the sign

of equality and a nought. Next came more reflection, with closed

eyes, and a fresh row of letters arranged in a different order and

likewise followed by a nought. Page after page was filled in this

queer fashion, each line winding up with 0.



'What are you doing with all those rows of figures amounting to

zero? ' I asked him one day.



The mathematician gave me a leery look, picked up in barracks. A

sarcastic droop in the corner of his eye showed how he pitied my

ignorance. My colleague of the many noughts did not, however, take

an unfair advantage of his superiority. He told me that he was

working at analytical geometry.



The phrase had a strange effect upon me. I ruminated silently to

this purpose: there was a higher geometry, which you learnt more

particularly with combinations of letters in which x and y played a

prominent part. When my next-door neighbor reflected so long,

clutching his forehead between his hands, he was trying to discover

the hidden meaning of his own hieroglyphics; he saw the ghostly

translation of his sums dancing in space. What did he perceive?

How would the alphabetical signs, arranged first in one and then in

another manner, give an image of the actual things, an image

visible to the eyes of the mind alone? It beat me.



'I shall have to learn analytical geometry some day,' I said.

'Will you help me? '



'I'm quite willing,' he replied, with a smile in which I read his

lack of confidence in my determination.



No matter; we struck a bargain that same evening. We would

together break up the stubble of algebra and analytical geometry,

the foundation of the mathematical degree; we would make common

stock: he would bring long hours of calculation, I my youthful

ardor. We would begin as soon as I had finished with my arts

degree, which was my main preoccupation for the moment.



In those far off days it was the rule to make a little serious

literary study take precedence of science. You were expected to be

familiar with the great minds of antiquity, to converse with Horace

and Virgil, Theocritus and Plato, before touching the poisons of

chemistry or the levers of mechanics. The niceties of thought

could only be the gainers by these preparations. Life's

exigencies, ever harsher as progress afflicts us with its

increasing needs, have changed all that. A fig for correct

language! Business before all!



This modern hurry would have suited my impatience. I confess that

I fumed against the regulation which forced Latin and Greek upon me

before allowing me to open up relations with the sine and cosine.

Today, wiser, ripened by age and experience, I am of a different

opinion. I very much regret that my modest literary studies were

not more carefully conducted and further prolonged. To fill up

this enormous blank a little, I respectfully returned, somewhat

late in life, to those good old books which are usually sold

second-hand with their leaves hardly cut. Venerable pages,

annotated in pencil during the long evenings of my youth, I have

found you again and you are more than ever my friends. You have

taught me that an obligation rests upon whoever wields the pen: he

must have something to say that is capable of interesting us. When

the subject comes within the scope of natural science, the interest

is nearly always assured; the difficulty, the great difficulty, is

to prune it of its thorns and to present it under a prepossessing

aspect. Truth, they say, rises naked from a well. Agreed; but

admit that she is all the better for being decently clothed. She

craves, if not the gaudy furbelows borrowed from rhetoric's

wardrobe, at least a vine leaf. The geometers alone have the right

to refuse her that modest garment; in theorems, plainness suffices.

The others, especially the naturalist, are in duty bound to drape a

gauze tunic more or less elegantly around her waist.



Suppose I say: 'Baptiste, give me my slippers.'



I am expressing myself in plain language, a little poor in

variants. I know exactly what I am saying and my speech is

understood.



Others--and they are numerous--contend that this rudimentary method

is the best in all things. They talk science to their readers as

they might talk slippers to Baptiste. Kaffir syntax does not shock

them. Do not speak to them of the value of a well selected term,

set down in its right place, still less of a lilting construction,

sounding rather well. Childish nonsense they call all that; the

fiddling of a short sighted mind!



Perhaps they are right: the Baptiste idiom is a great economizer of

time and trouble. This advantage does not tempt me; it seems to me

that an idea stands out better if expressed in lucid language, with

sober imagery. A suitable phrase, placed in its correct position

and saying without fuss the things we want to say, necessitates a

choice, an often laborious choice. There are drab words, the

commonplaces of colloquial speech; and there are, so to speak,

colored words, which may be compared with the brushstrokes strewing

patches of light over the gray background of a painting. How are

we to find those picturesque words, those striking features which

arrest the attention? How are we to group them into a language

heedful of syntax and not displeasing to the ear?



I was taught nothing of this art. For that matter, is it ever

taught in the schools? I greatly doubt it. If the fire that runs

through our veins, if inspiration do not come to our aid, we shall

flutter the pages of the thesaurus in vain: the word for which we

seek will refuse to come. Then to what masters shall we have

recourse to quicken and develop the humble germ that is latent

within us? To books.



As a boy, I was always an ardent reader; but the niceties of a

well-balanced style hardly interested me: I did not understand

them. A good deal later, when close upon fifteen, I began vaguely

to see that words have a physiognomy of their own. Some pleased me

better than others by the distinctness of their meaning and the

resonance of their rhythm; they produced a clearer image in my

mind; after their fashion, they gave me a picture of the object

described. Colored by its adjective and vivified by its verb, the

name became a living reality: what it said I saw. And thus,

gradually, was the magic of words revealed to me, when the chances

of, my undirected reading placed a few easy standard pages in my

way.



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