SCIENTIFIC METHOD--GILBERT, GALILEO, HARVEY, DESCARTES
The previous chapter has given some indication of the range of the
material which was demanding scientific investigation at the end of the
sixteenth and the beginning of the seventeenth century. The same period
witnessed a conscious development of the method, or methods, of
investigation. As we have seen, Bacon wrote in 1620 a considerable work,
_The New Logic_ (_Novum Organum_), so called to distinguish it from the
traditional deductive logic. It aimed to furnish the organ or
instrument, to indicate the correct mental procedure, to be employed in
the discovery of natural law. Some seventeen years later, the
illustrious Frenchman René Descartes (1596-1650) published his
_Discourse on the Method of rightly conducting the Reason and seeking
Truth in the Sciences_. Both of these philosophers illustrated by their
own investigations the efficiency of the methods which they advocated.
[Illustration: _Painting by A. Ackland Hunt_
DR. GILBERT SHOWING HIS ELECTRICAL EXPERIMENTS TO QUEEN ELIZABETH AND
HER COURT]
Before 1620, however, the experimental method had already yielded
brilliant results in the hands of other scientists. We pass over
Leonardo da Vinci and many others in Italy and elsewhere, whose names
should be mentioned if we were tracing this method to its origin. By
1600 William Gilbert (1540-1603), physician to Queen Elizabeth, before
whom, as a picture in his birthplace illustrates, he was called to
demonstrate his discoveries, had published his work on the Magnet, the
outcome of about eighteen years of critical research. He may be
considered the founder of electrical science. Galileo, who discovered
the fundamental principles of dynamics and thus laid the basis of modern
physical science, although he did not publish his most important work
till 1638, had even before the close of the sixteenth century prepared
the way for the announcement of his principles by years of strict
experiment. By the year 1616, William Harvey (1578-1657), physician at
the court of James I, and, later, of Charles I, had, as the first modern
experimental physiologist, gained important results through his study of
the circulation of the blood.
It is not without significance that both Gilbert and Harvey had spent
years in Italy, where, as we have implied, the experimental method of
scientific research was early developed. Harvey was at Padua (1598-1602)
within the time of Galileo's popular professoriate, and may well have
been inspired by the physicist to explain on dynamical principles the
flow of blood through arteries and veins. This conjecture is the more
probable, since Galileo, like Harvey and Gilbert, had been trained in
the study of medicine. Bacon in turn had in his youth learned something
of the experimental method on the Continent of Europe, and, later, was
well aware of the studies of Gilbert and Galileo, as well as of Harvey,
who was indeed his personal physician.
Although these facts seem to indicate that method may be transmitted in
a nation or a profession, or through personal association, there still
remains some doubt as to whether anything so intimate as the mental
procedure involved in invention and in the discovery of truth can be
successfully imparted by instruction. The individuality of the man of
genius engaged in investigation must remain a factor difficult to
analyze. Bacon, whose purpose was to hasten man's empire over nature
through increasing the number of inventions and discoveries, recognized
that the method he illustrated is not the sole method of scientific
investigation. In fact, he definitely states that the method set forth
in the _Novum Organum_ is not original, or perfect, or indispensable. He
was aware that his method tended to the ignoring of genius and to the
putting of intelligences on one level. He knew that, although it is
desirable for the investigator to free his mind from prepossessions, and
to avoid premature generalizations, interpretation is the true and
natural work of the mind when free from impediments, and that the
conjecture of the man of genius must at times anticipate the slow
process of painful induction. As we shall see in the nineteenth chapter,
the psychology of to-day does not know enough about the workings of the
mind to prescribe a fixed mental attitude for the investigator.
Nevertheless, Bacon was not wrong in pointing out the virtues of a
method which he and many others turned to good account. Let us first
glance, however, at the activities of those scientists who preceded
Bacon in the employment of the experimental method.
Gilbert relied, in his investigations, on oft-repeated and verifiable
experiments, as can be seen from his work _De Magnete_. He directs the
experimenter, for example, to take a piece of loadstone of convenient
size and turn it on a lathe to the form of a ball. It then may be
called a _terrella_, or earthkin. Place on it a piece of iron wire. The
ends of the wire move round its middle point and suddenly come to a
standstill. Mark with chalk the line along which the wire lies still and
sticks. Then move the wire to other spots on the _terrella_ and repeat
your procedure. The lines thus marked, if produced, will form meridians,
all coming together at the poles. Again, place the magnet in a wooden
vessel, and then set the vessel afloat in a tub or cistern of still
water. The north pole of the stone will seek approximately the direction
of the south pole of the earth, etc. It was on the basis of scores of
experiments of this sort, carried on from about 1582 till 1600, that
Gilbert felt justified in concluding that the terrestrial globe is a
magnet. This theory has since that time been abundantly confirmed by
navigators. The full title of his book is _Concerning the Magnet and
Magnetic Bodies, and concerning the Great Magnet the Earth: A New
Natural History (Physiologia) demonstrated by many Arguments and
Experiments_. It does not detract from the credit of Gilbert's result to
state that his initial purpose was not to discover the nature of
magnetism or electricity, but to determine the true substance of the
earth, the innermost constitution of the globe. He was fully conscious
of his own method and speaks with scorn of certain writers who, having
made no magnetical experiments, constructed ratiocinations on the basis
of mere opinions and old-womanishly dreamed the things that were not.
Galileo (1564-1642) even as a child displayed something of the
inventor's ingenuity, and when he was nineteen, shortly after the
beginning of Gilbert's experiments, his keen perception for the
phenomena of motion led to his making a discovery of great scientific
moment. He observed a lamp swinging by a long chain in the cathedral of
his native city of Pisa, and noticed that, no matter how much the range
of the oscillations might vary, their times were constant. He verified
his first impressions by counting his pulse, the only available
timepiece. Later he invented simple pendulum devices for timing the
pulse of patients, and even made some advances in applying his discovery
in the construction of pendulum clocks.
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In 1589 he was appointed professor of mathematics in the University of
Pisa, and within a year or two established through experiment the
foundations of the science of dynamics. As early as 1590 he put on
record, in a Latin treatise _Concerning Motion_ (_De Motu_), his dissent
from the theories of Aristotle in reference to moving bodies, confuting
the Philosopher both by reason and ocular demonstration. Aristotle had
held that two moving bodies of the same sort and in the same medium have
velocities in proportion to their weights. If a moving body, whose
weight is represented by _b_, be carried through the line _c--e_ which
is divided in the point _d_, if, also, the moving body is divided
according to the same proportion as line _c--e_ is in the point _d_, it
is manifest that in the time taken to carry the whole body through
_c--e_, the part will be moved through _c--d_. Galileo said that it is
as clear as daylight that this view is ridiculous, for who would
believe that when two lead spheres are dropped from a great height, the
one being a hundred times heavier than the other, if the larger took an
hour to reach the earth, the smaller would take a hundred hours? Or,
that if from a high tower two stones, one twice the weight of the other,
should be pushed out at the same moment, the larger would strike the
ground while the smaller was still midway? His biography tells that
Galileo in the presence of professors and students dropped bodies of
different weights from the height of the Leaning Tower of Pisa to
demonstrate the truth of his views. If allowance be made for the
friction of the air, all bodies fall from the same height in equal
times: the final velocities are proportional to the times; the spaces
passed through are proportional to the squares of the times. The
experimental basis of the last two statements was furnished by means of
an inclined plane, down a smooth groove in which a bronze ball was
allowed to pass, the time being ascertained by means of an improvised
water-clock.
Galileo's mature views on dynamics received expression in a work
published in 1638, _Mathematical Discourses and Demonstrations
concerning Two New Sciences relating to Mechanics and Local Movements_.
It treats of cohesion and resistance to fracture (strength of
materials), and uniform, accelerated, and projectile motion (dynamics).
The discussion is in conversation form. The opening sentence shows
Galileo's tendency to base theory on the empirical. It might be freely
translated thus: "Large scope for intellectual speculation, I should
think, would be afforded, gentlemen, by frequent visits to your famous
Venetian Dockyard (_arsenale_), especially that part where mechanics are
in demand; seeing that there every sort of instrument and machine is put
to use by numbers of workmen, among whom, taught both by tradition and
their own observation, there must be some very skillful and also able to
talk." The view of the shipbuilders, that a large galley before being
set afloat is in greater danger of breaking under its own weight than a
small galley, is the starting-point of this most important of Galileo's
contributions to science.
Vesalius (1514-1564) had in his work on the structure of the human body
(_De Humani Corporis Fabrica_, 1543) shaken the authority of Galen's
anatomy; it remained for Harvey on the basis of the new anatomy to
improve upon the Greek physician's experimental physiology. Harvey
professed to learn and teach anatomy, not from books, but from
dissections, not from the dogmas of the philosophers, but from the
fabric of nature.
There have come down to us notes of his lectures on anatomy delivered
first in 1616. A brief extract will show that even at that date he had
already formulated a theory of the circulation of the blood:--
"[Illustration: WH monogram][1] By the structure of the heart it appears
that the blood is continually transfused through the lungs to the
aorta--as by the two clacks of a water-ram for raising water.
"It is shown by ligature that there is continuous motion of the blood
from arteries to veins.
"Whence Δ it is demonstrated that there is a continuous motion of the
blood in a circle, affected by the beat of the heart."
It was not till 1628 that Harvey published his _Anatomical Disquisition
on the Motion of the Heart and Blood in Animals_. It gives the
experimental basis of his conclusions. If a live snake be laid open, the
heart will be seen pulsating and propelling its contents. Compress the
large vein entering the heart, and the part intervening between the
point of constriction and the heart becomes empty and the organ pales
and shrinks. Remove the pressure, and the size and color of the heart
are restored. Now compress the artery leading from the organ, and the
part between the heart and the point of pressure, and the heart itself,
become distended and take on a deep purple color. The course of the
blood is evidently from the vena cava through the heart to the aorta.
Harvey in his investigations made use of many species of animals--at
least eighty-seven.
It was believed by some, before Harvey's demonstrations, that the
arteries were hollow pipes carrying air from the lungs throughout the
body, although Galen had shown by cutting a dog's trachea, inflating the
lungs and tying the trachea, that the lungs were in an enclosing sack
which retained the air. Harvey, following Galen, held that the pulmonary
artery, carrying blood to the lungs from the right side of the heart,
and the pulmonary veins, carrying blood from the lungs to the left side
of the heart, intercommunicate in the hidden porosities of the lungs and
through minute inosculations.
In man the vena cava carries the blood to the right side of the heart,
the pulmonary artery inosculates with the pulmonary veins, which convey
it to the left side of the heart. This muscular pump drives it into the
aorta. It still remains to be shown that in the limbs the blood passes
from the arteries to the veins. Bandage the arm so tightly that no pulse
is felt at the wrist. The hand appears at first natural, and then grows
cold. Loose the bandage sufficiently to restore the pulse. The hand and
forearm become suffused and swollen. In the first place the supply of
blood from the deep-lying arteries is cut off. In the second case the
blood returning by the superficial veins is dammed back. In the limbs as
in the lungs the blood passes from artery to vein by anastomoses and
porosities. All these arteries have their source in the aorta; all these
veins pour their stream ultimately into the vena cava. The veins have
valves, which prevent the blood flowing except toward the heart. Again,
the veins and arteries form a connected system; for through either a
vein or an artery all the blood may be drained off. The arguments by
which Harvey supported his view were various. The opening clause of his
first chapter, "When I first gave my mind to vivisection as a means of
discovering the motions and uses of the heart," throws a strong light on
his special method of experimental investigation.
Bacon, stimulated by what he called _philanthropia_, always aimed, as we
have seen, to establish man's control over nature. But all power of a
high order depends on an understanding of the essential character, or
law, of heat, light, sound, gravity, and the like. Nothing short of a
knowledge of the underlying nature of phenomena can give science
advantage over chance in hitting upon useful discoveries and inventions.
It is, therefore, natural to find him applying his method of
induction--his special method of true induction--to the investigation of
heat.
In the first place, let there be mustered, without premature
speculation, all the instances in which heat is manifested--flame,
lightning, sun's rays, quicklime sprinkled with water, damp hay, animal
heat, hot liquids, bodies subjected to friction. Add to these, instances
in which heat seems to be absent, as moon's rays, sun's rays on
mountains, oblique rays in the polar circle. Try the experiment of
concentrating on a thermoscope, by means of a burning-glass, the moon's
rays. Try with the burning-glass to concentrate heat from hot iron, from
common flame, from boiling water. Try a concave glass with the sun's
rays to see whether a diminution of heat results. Then make record of
other instances, in which heat is found in varying degrees. For example,
an anvil grows hot under the hammer. A thin plate of metal under
continuous blows might grow red like ignited iron. Let this be tried as
an experiment.
After the presentation of these instances induction itself must be set
to work to find out what factor is ever present in the positive
instances, what factor is ever wanting in the negative instances, what
factor always varies in the instances which show variation. According to
Bacon it is in the process of exclusion that the foundations of true
induction are laid. We can be certain, for example, that the essential
nature of heat does not consist in light and brightness, since it is
present in boiling water and absent in the moon's rays.
The induction, however, is not complete till something positive is
established. At this point in the investigation it is permissible to
venture an hypothesis in reference to the essential character of heat.
From a survey of the instances, all and each, it appears that the nature
of which heat is a particular case is motion. This is suggested by
flame, simmering liquids, the excitement of heat by motion, the
extinction of fire by compression, etc. Motion is the genus of which
heat is the species. Heat itself, its essence, is motion and nothing
else.
It remains to establish its specific differences. This accomplished, we
arrive at the definition: Heat is a motion, expansive, restrained, and
acting in its strife upon the smaller particles of bodies. Bacon,
glancing toward the application of this discovery, adds: "_If in any
natural body you can excite a dilating or expanding motion, and can so
repress this motion and turn it back upon itself, that the dilation
shall not proceed equally, but have its way in one part and be
counteracted in another, you will undoubtedly generate heat._" The
reader will recall that Bacon looked for the invention of instruments
that would generate heat solely by motion.
Descartes was a philosopher and mathematician. In his _Discourse on
Method_ and his _Rules for the Direction of the Mind_ (1628) he laid
emphasis on deduction rather than on induction. In the subordination of
particulars to general principles he experienced a satisfaction akin to
the sense of beauty or the joy of artistic production. He speaks
enthusiastically of that pleasure which one feels in truth, and which
in this world is about the only pure and unmixed happiness.
At the same time he shared Bacon's distrust of the Aristotelian logic
and maintained that ordinary dialectic is valueless for those who desire
to investigate the truth of things. There is need of a method for
finding out the truth. He compares himself to a smith forced to begin at
the beginning by fashioning tools with which to work.
In his method of discovery he determined to accept nothing as true that
he did not clearly recognize to be so. He stood against assumptions, and
insisted on rigid proof. Trust only what is completely known. Attain a
certitude equal to that of arithmetic and geometry. This attitude of
strict criticism is characteristic of the scientific mind.
Again, Descartes was bent on analyzing each difficulty in order to solve
it; to neglect no intermediate steps in the deduction, but to make the
enumeration of details adequate and methodical. Preserve a certain
order; do not attempt to jump from the ground to the gable, but rise
gradually from what is simple and easily understood.
Descartes' interest was not in the several branches of mathematics;
rather he wished to establish a universal mathematics, a general science
relating to order and measurement. He considered all physical nature,
including the human body, as a mechanism, capable of explanation on
mathematical principles. But his immediate interest lay in numerical
relationships and geometrical proportions.
Recognizing that the understanding was dependent on the other powers of
the mind, Descartes resorted in his mathematical demonstrations to the
use of lines, because he could find no method, as he says, more simple
or more capable of appealing to the imagination and senses. He
considered, however, that in order to bear the relationships in memory
or to embrace several at once, it was essential to explain them by
certain formulæ, the shorter the better. And for this purpose it was
requisite to borrow all that was best in geometrical analysis and
algebra, and to correct the errors of one by the other.
Descartes was above all a mathematician, and as such he may be regarded
as a forerunner of Newton and other scientists; at the same time he
developed an exact scientific method, which he believed applicable to
all departments of human thought. "Those long chains of reasoning," he
says, "quite simple and easy, which geometers are wont to employ in the
accomplishment of their most difficult demonstrations, led me to think
that everything which might fall under the cognizance of the human mind
might be connected together in the same manner, and that, provided only
one should take care not to receive anything as true which was not so,
and if one were always careful to preserve the order necessary for
deducing one truth from another, there would be none so remote at which
he might not at last arrive, or so concealed which he might not
discover."
REFERENCES
Francis Bacon, _Philosophical Works_ (Ellis and Spedding edition), vol.
IV, Novum Organum.
J. J. Fahie, _Galileo; His Life and Work_.
Galileo, _Two New Sciences_; translated by Henry Crew and Alphonse De
Salvio.
William Gilbert, _On the Loadstone_; translated by P. F. Mottelay.
William Harvey, _An Anatomical Disquisition on the Motion of the Heart
and Blood in Animals_.
T. H. Huxley, _Method and Results_.
D'Arcy Power, _William Harvey_ (in _Masters of Medicine_).
FOOTNOTES:
[1] This is Harvey's monogram, which he used in his notes to mark any
original observation.