Chapter V (6)

[780] The supposition, that volcanic agencies were formerly more potent
than they are now, is by no means inconsistent with the scientific
doctrine of uniformity, though it is generally considered to be
so. It is one thing to assert the uniformity of natural laws; it
is quite another thing to assert the uniformity of natural causes.
Heat may once have produced far greater effects than it can do at
present, and yet the laws of nature be unchanged, and the order
and sequence of events unbroken. What I would venture to suggest
to geologists is, that they have not taken sufficiently into
account the theory of the interchange of forces, which seems to
offer a solution of at least part of the problem. For, by that
theory, a large portion of the heat which formerly existed may
have been metamorphosed into other forces, such as light, chemical
affinity, and gravitation. The increase of these forces consequent
on the diminution of heat, would have facilitated the
consolidation of matter; and until such forces possessed a certain
energy, water, which afterwards became so prominent, could not
have been formed. If the power of chemical affinity, for instance,
were much weaker than it is, water would assuredly resolve itself
into its component gases. Without wishing to lay too much stress
on this speculation, I submit it to the consideration of competent
judges, because I am convinced that any hypothesis, not absolutely
inconsistent with the known laws of nature, is preferable to that
dogma of interference, which what may be called the miraculous
school of geologists wish to foist upon us, in utter ignorance of
its incompatibility with the conclusions of the most advanced
minds in other departments of thought.

The remarks in Sir Roderick Murchison's great work (_Siluria_,
London, 1854, pp. 475, 476) on the 'grander intensity of former
causation,' and on the difficulty this opposes to the
'uniformitarians,' apply merely to those who take for granted that
_each_ force has always been equally powerful: they do not affect
those who suppose that it is only the _aggregate_ of force which
remains unimpaired. Though the distribution of forces may be
altered, their gross amount is not susceptible of change, so far
as the highest conceptions of our actual science extend.
Consequently, there is no need for us to believe that, in
different periods, the intensity of causation varies; though we
may believe that some one agent, such as heat, had at one time
more energy than it has ever had since.

[781] 'The great agents of change in the inorganic world may be divided
into two principal classes, the aqueous and the igneous. To the
aqueous belong rain, rivers, torrents, springs, currents, and
tides; to the igneous, volcanos and earthquakes. Both these
classes are instruments of decay as well as of reproduction; but
they may also be regarded as antagonist forces. For the aqueous
agents are incessantly labouring to reduce the inequalities of the
earth's surface to a level; while the igneous are equally active
in restoring the unevenness of the external crust, partly by
heaping up new matter in certain localities, and partly by
depressing one portion, and forcing out another, of the earth's
envelope.' _Lyell's Principles of Geology_, 9th edit., London,
1853, p. 198.

When geologists began to study the laws according to which fire and water had altered the structure of the earth, two different courses were open to them, namely, the inductive and the deductive. The deductive plan was to compute the probable consequences of fire and water, by reasoning from the sciences of thermotics and hydrodynamics; tracking each element by an independent line of argument, and afterwards coördinating into a single scheme the results which had been separately obtained. It would then only remain to inquire, how far this imaginary scheme harmonized with the actual state of things; and if the discrepancy between the ideal and the actual were not greater than might fairly be expected from the perturbations produced by other causes, the ratiocination would be complete, and geology would, in its inorganic department, become a deductive science. That our knowledge is ripe for such a process, I am far, indeed, from supposing; but this is the path which a deductive mind would take, so far as it was able. On the other hand, an inductive mind, instead of beginning with fire and water, would begin with the effects which fire and water had produced, and would first study these two agents, not in their own separate sciences, but in their united action as exhibited on the crust of the earth. An inquirer of this sort would assume, that the best way of arriving at truth would be to proceed from effects to causes, observing what had actually happened, and rising from the complex results up to a knowledge of the simple agents, by whose power the results have been brought about.

If the reader has followed the train of thought which I have endeavoured to establish in this chapter, and in the first volume, he will be prepared to expect that when, in the latter half of the eighteenth century, geology was first seriously studied, the inductive plan of proceeding from effects to causes became the favourite one in England; while the deductive plan of proceeding from causes to effects, was adopted in Scotland and in Germany. And such was really the case. It is generally admitted, that, in England, scientific geology owes its origin to William Smith, whose mind was singularly averse to system, and who, believing that the best way of understanding former causes was to study present effects, occupied himself, between the years 1790 and 1815, in a laborious examination of different strata.[782] In 1815, he, after traversing the whole of England on foot, published the first complete geological map which ever appeared, and thus took the first great step towards accumulating the materials for an inductive generalization.[783] In 1807, and, therefore, before he had brought his arduous task to an end, there was formed in London the Geological Society, the express object of which, we are assured, was, to observe the condition of the earth, but by no means to generalize the causes which had produced that condition.[784] The resolution was, perhaps, a wise one. At all events, it was highly characteristic of the sober and patient spirit of the English intellect. With what energy and unsparing toil it has been executed, and how the most eminent members of the Geological Society have, in the pursuit of truth, not only explored every part of Europe, but examined the shell of the earth in America and in Northern Asia, is well known to all who are interested in these matters; nor can it be denied, that the great works of Lyell and Murchison prove that the men who are capable of such laborious enterprises, are also capable of the still more difficult achievement of generalizing their facts and refining them into ideas. They did not go as mere observers, but they went with the noble object of making their observations subservient to a discovery of the laws of nature. That was their aim; and all honour be to them for it. Still, it is evident, that their process is essentially inductive; it is a procedure from the observation of complex phenomena, up to the elements to which those phenomena are owing; it is, in other words, a study of natural effects, in order to learn the operation of natural causes.

[782] Dr. Whewell, comparing him with his great German contemporary,
Werner, says, 'In the German, considering him as a geologist, the
ideal element predominated.' ... 'Of a very different temper and
character was William Smith. No literary cultivation of his youth
awoke in him the _speculative love of symmetry and system_; but a
singular clearness and precision of the classifying power, which
he possessed as a native talent, was exercised and developed by
exactly those geological facts among which his philosophical task
lay.' ... 'We see great vividness of thought and activity of mind,
_unfolding itself exactly in proportion to the facts with which it
had to deal_.' ... 'He dates his attempts to discriminate and
connect strata from the year 1790.' _Whewell's History of the
Inductive Sciences_, London, 1847, vol. iii. pp. 562-564.

[783] 'The execution of his map was completed in 1815, and remains a
lasting monument of original talent and extraordinary
perseverance; for he had explored the whole country on foot
without the guidance of previous observers, or the aid of
fellow-labourers, and had succeeded in throwing into natural
divisions the whole complicated series of British rocks.' _Lyell's
Principles of Geology_, p. 58. Geological maps of parts of England
had, however, been published before 1815. See _Conybeare on
Geology_, in _Second Report of the British Association_, p. 373.

[784] 'A great body of new data were required; and the Geological
Society of London, founded in 1807, conduced greatly to the
attainment of this desirable end. To multiply and record
observations, and patiently to await the result at some future
period, was the object proposed by them; and it was their
favourite maxim, that the time was not yet come for a general
system of geology, but that all must be content for many years to
be exclusively engaged in furnishing materials for future
generalizations.' _Lyell's Principles of Geology_, p. 59. Compare
_Richardson's Geology_, 1851, p. 40.

Very different was the process in Germany and Scotland. In 1787, that is, only three years before William Smith began his labours, Werner, by his work on the classification of mountains, laid the foundation of the German school of geology.[785] His influence was immense; and among his pupils we find the names of Mohs, Raumer, and Von Buch, and even that of Alexander Humboldt.[786] But the geological theory which he propounded, depended entirely on a chain of argument from cause to effect. He assumed, that all the great changes through which the earth had passed, were due to the action of water. Taking this for granted, he reasoned deductively from premisses with which his knowledge of water supplied him. Without entering into details respecting his system, it is enough to say, that, according to it, there was originally one vast and primeval sea, which, in the course of time, deposited the primitive rocks. The base of all was granite; then gneiss; and others followed in their order. In the bosom of the water, which at first was tranquil, agitations gradually arose, which, destroying part of the earliest deposits, gave birth to new rocks, formed out of their ruins. The stratified thus succeeded to the unstratified, and something like variety was established. Then came another period, in which the face of the waters, instead of being merely agitated, was convulsed by tempests, and, amid their play and collision, life was generated, and plants and animals sprung into existence. The vast solitude was slowly peopled, the sea gradually retired; and a foundation was laid for that epoch, during which man entered the scene, bringing with him the rudiments of order and of social improvement.[787]

[785] Cuvier, in his Life of Werner, says (_Biographie Universelle_,
vol. i. pp. 376, 377), 'La connaissance des positions respectives
des minéraux dans la croûte du globe, et ce que l'on peut en
conclure relativement aux époques de leur origine, forment une
autre branche de la science qu'il appelle Géognosie. Il en
présenta les premières bases en 1787, dans un petit écrit intitulé
"Classification et description des Montagnes."'

[786] _Whewell's History of the Inductive Sciences_, vol. iii. p. 567.

[787] 'Une mer universelle et tranquille dépose en grandes masses les
roches primitives, roches nettement cristallisées, où domine
d'abord la silice. Le granit fait la base de tout; au granit
succède le gneiss, qui n'est qu'un granit commençant à se
feuilleter.' ... 'Des agitations intestines du liquide détruisent
une partie de ces premiers dépôts; de nouvelles roches se forment
de leurs débris réunis par des cimens. C'est parmi ces tempêtes
que naît la vie.' ... 'Les eaux, de nouveau tranquillisées, mais
dont le contenu a changé, déposent des couches moins épaisses et
plus variées, où les débris des corps vivans s'accumulent
successivement dans un ordre non moins fixe que celui des roches
qui les contiennent. Enfin, la dernière retraite des eaux répand
sur le continent d'immenses alluvions de matières meubles,
premiers sièges de la végétation, de la culture et de la
sociabilité.' _Eloge de Werner_, in _Cuvier_, _Recueil des Elogés
Historiques_, vol. ii. pp. 321-323.

These were the leading views of a system which, we must remember, exercised great sway in the scientific world, and won over to its side minds of considerable power. Erroneous and far-fetched though it was, it had the merit of calling attention to one of the two chief principles which have determined the present condition of our planet. It had the further merit of provoking a controversy, which was eminently serviceable to the interests of truth. For, the great enemy of knowledge is not error, but inertness. All that we want is discussion, and then we are sure to do well, no matter what our blunders may be. One error conflicts with another; each destroys its opponent, and truth is evolved. This is the course of the human mind, and it is from this point of view that the authors of new ideas, the proposers of new contrivances, and the originators of new heresies, are benefactors of their species. Whether they are right or wrong, is the least part of the question. They tend to excite the mind; they open up the faculties; they stimulate us to fresh inquiry; they place old subjects under new aspects; they disturb the public sloth; and they interrupt, rudely, but with most salutary effect, that love of routine, which, by inducing men to go grovelling on in the ways of their ancestors, stands in the path of every improvement, as a constant, an outlying, and, too often, a fatal obstacle.

The method adopted by Werner was evidently deductive, since he argued from a supposed cause, and reasoned from it to the effects. In that cause, he found his major premiss, and thence he worked downwards to his conclusion, until he reached the world of sense and of reality. He trusted in his one great idea, and he handled that idea with consummate skill. On that very account, did he pay less attention to existing facts. Had he chosen, he, like other men, could have collected them, and subjected them to an inductive generalization. But he preferred the opposite path. To reproach him with this is irrational; for, in his journey after truth, he chose one of the only two roads which are open to the human mind. In England, indeed, we are apt to take for granted that one road is infinitely preferable to the other. It may be so; but on this, as on many other subjects, assertions are current which have never been proved. At all events, Werner was so satisfied with his method, that he would not be at the pains of examining the position of rocks and their strata, as they are variously exhibited in different countries; he did not even explore his own country, but, confining himself to a corner of Germany, he began and completed his celebrated system, without investigating the facts on which, according to the inductive method, that system should have been built.[788]

[788] 'If it be true that delivery be the first, second, and third
requisite in a popular orator, it is no less certain that to
travel is of first, second, and third importance to those who
desire to originate just and comprehensive views concerning the
structure of our globe. Now, Werner had not travelled to distant
countries: he had merely explored a small portion of Germany, and
conceived, and persuaded others to believe, that the whole surface
of our planet, and all the mountain chains in the world, were made
after the model of his own province.' ... 'It now appears that he
had misinterpreted many of the most important appearances even in
the immediate neighbourhood of Freyberg. Thus, for example, within
a day's journey of his school, the porphyry, called by him
primitive, has been found not only to send forth veins, or dykes,
through strata of the coal formation, but to overlie them in
mass.' _Lyell's Principles of Geology_, p. 47.

Exactly the same process, on the same subject, and at the same time, was going on in Scotland. Hutton, who was the founder of Scotch geology, and who, in 1788, published his _Theory of the Earth_, conducted the inquiry just as Werner did; though, when he began his speculations, he had no knowledge of what Werner was doing.[789] The only difference between them was, that while Werner reasoned from the agency of water, Hutton reasoned from the agency of fire. The cause of this may, I think, be explained. Hutton lived in a country where some of the most important laws of heat had, for the first time, been generalized, and where consequently, that department of inorganic physics had acquired great reputation. It was natural for a Scotchman to take more than ordinary interest in a subject in which Scotland had been so successful, and had obtained so much fame. We need not, therefore, wonder that Hutton, who, like all men, felt the intellectual bent of the time in which he lived, should have yielded to an influence of which he was, perhaps, unconscious. In obedience to the general mental habits of his country he adopted the deductive method. In further obedience to the more special circumstances connected with his own immediate pursuits, he gathered the principles from which he reasoned from a study of fire, instead of gathering them, as Werner did, from a study of water.

[789] Though Hutton's _Theory of the Earth_ was first published in 1788,
the edition of 1795, which is the one I have used, contains a
great number of additional illustrations of his views, and was
evidently re-written. But the main features are the same; and we
learn from his friend, Playfair, that 'the great outline of his
system' was completed 'several years' before 1788. _Life of
Hutton_, in _Playfair's Works_, vol. iv. p. 50, Edinburgh, 1822.

Hence it is, that, in the history of geology, the followers of Werner are known as Neptunists, and those of Hutton as Plutonists.[790] And these terms represent the only difference between the two great masters. In the most important points, namely their method, they were entirely agreed. Both were essentially one-sided; both paid a too exclusive attention to one of the two principal agents which have altered, and are still altering, the crust of the earth; both reasoned from those agents, instead of reasoning to them; and both constructed their system without sufficiently studying the actual and existing facts; committing, in this respect, an error which the English geologists were the first to rectify.

[790] Kirwan appears to have been the first who called Hutton's theory
'the Plutonic System.' See _Illustrations of the Huttonian
Theory_, in _Playfair's Works_, vol. i. p. 145. On the distinction
between Neptunists and Plutonists, see the same work, pp. 504,
505.

As I am writing a history, not of science, but of scientific method, I can only briefly glance at the nature of those services which Hutton rendered to geology, and which are so considerable, that his system has been called its present basis.[791] This, however, is too strongly expressed; for, though Hutton was far from denying the influence of water,[792] he did not concede enough to it, and there is a tendency among several geologists to admit that the system of Werner considered as an aqueous theory, contains a larger amount of truth than the advocates of the igneous theory are willing to allow. Still, what Hutton did was most remarkable, especially in reference to what are now termed metamorphic rocks, the theory of whose formation he was the first to conceive.[793] Into this, and into their connexion, on the one hand, with the sedimentary rocks, and, on the other hand, with those rocks whose origin is perhaps purely igneous, I could not enter without treading on debatable ground. But, putting aside what is yet uncertain, I will mention two circumstances respecting Hutton which are undisputed, and which will give some idea of his method, and of the turn of his mind. The first circumstance is, that, although he ascribed to subterranean heat, as exhibited in volcanic action, a greater and more constant energy than any previous inquirers had ventured to do,[794] he preferred speculating on the probable consequences of that action, rather than drawing inferences from the facts which the action presented; he being on this point so indifferent, that he arrived at his conclusions without inspecting even a single region of active volcanoes, where he might have watched the workings of nature, and seen what she was really about.[795] The other circumstance is equally characteristic. Hutton, in his speculations concerning the geological effects of heat, naturally availed himself of the laws which Black had unfolded. One of those laws was, that certain earths owe their fusibility to the presence of fixed air in them before heat has expelled it; so that if it were possible to force them to retain their fixed air, or carbonic acid gas, as we now call it, no amount of heat could deprive them of the capability of being fused. The fertile mind of Hutton saw, in this discovery, a principle from which he could construct a geological argument. It occurred to him, that great pressure would prevent the escape of fixed air from heated rocks, and would thus enable them to be fused, notwithstanding their elevated temperature. He then supposed that, at a period anterior to the existence of man, such a process had taken place under the surface of the sea, and that the weight of so great a column of water had prevented the rocks from being decomposed while they were subjected to the action of fire. In this way, their volatile parts were held together, and they themselves might be melted, which could not have happened except for this enormous pressure. By following this line of argument, he accounted for the consolidation of strata by heat; since, according to the premisses from which he started, the oily, or bituminous parts, would remain, in spite of the efforts of heat to disperse them.[796] This striking speculation led to the inference, that the volatile components of a substance, and its fixed components, may be made to cohere, in the very teeth of that apparently irresistible agent whose business it is to effect their separation. Such an inference was contrary to all experience; or, to say the least, no man had ever seen an instance of it.[797] Indeed, the event was only supposed to happen in consequence of circumstances which were never met with on the surface of the globe, and which, therefore, were out of the range of all human observation.[798] The utmost that could be expected was, that, by means of our instruments, we might, perhaps, on a small scale, imitate the process which Hutton had imagined. It was possible, that a direct experiment might artificially combine great pressure with great heat, and that the result might be, that the senses would realize what the intellect had conceived.[799] But the experiment had never been tried, and Hutton, who delighted in reasoning from ideas rather than from facts, was not likely to undertake it.[800] He cast his speculation on the world, and left it to its fate.[801] Fortunately, however, for the reception of his system, a very ingenious and skilful experimenter of that day, Sir James Hall, determined to test the speculation by an appeal to facts; and as nature did not supply the facts which he wanted, he created them for himself. He applied heat to powdered chalk, while, at the same time, with great delicacy of manipulation, he subjected the chalk to a pressure about equal to the weight of a column of water half a mile high. The result was, that, under that pressure, the volatile parts of the chalk were held together; the carbonic acid gas was unable to escape; the generation of quicklime was stopped; the ordinary operations of nature were baffled, and the whole composition, being preserved in its integrity, was fused, and, on subsequently cooling, actually crystallized into solid marble.[802] Never was triumph more complete. Never did a fact more fully confirm an idea.[803] But, in the mind of Hutton, the idea preceded the fact by a long interval; since, before the fact was known, the theory had been raised, and the system which was built upon it had, indeed, been published several years. It, therefore, appears that one of the chief parts of the Huttonian Theory, and certainly its most successful part, was conceived in opposition to all preceding experience; that it pre-supposed a combination of events which no one had ever observed, and the mere possibility of which nothing but artificial experiment could prove; and, finally, that Hutton was so confident of the validity of his own method of inquiry, that he disdained to make the experiment himself, but left to another mind that empirical branch of the investigation which he deemed of little moment, but which we, in England, are taught to believe is the only safe foundation of physical research.[804]

[791] 'Has not only supplanted that of Werner, but has formed the
foundation of the researches and writings of our most enlightened
observers, and is justly regarded as the basis of all sound
geology at the present day.' _Richardson's Geology_, London, 1851,
p. 38.

[792] _Hutton's Theory of the Earth_, Edinb. 1795, vol. i. pp. 34, 41,
192, 290, 291, 593, vol. ii. pp. 236, 369, 378, 555.

[793] 'In his writings, and in those of his illustrator, Playfair, we
find the germ of the metamorphic theory.' _Lyell's Manual of
Geology_, London, 1851, p. 92.

[794] The shortest summary of this view is in his _Theory of the Earth_,
Edin. 1795, vol. ii. pp. 556. 'The doctrine, therefore, of our
Theory is briefly this; that whatever may have been the operation
of dissolving water, and the chemical action of it upon the
materials accumulated at the bottom of the sea, the general
solidity of that mass of earth, and the placing of it in the
atmosphere above the surface of the sea, has been the immediate
operation of fire or heat melting and expanding bodies.'

[795] 'Although Hutton had never explored any region of active volcanos,
he had convinced himself that basalt and many other trap rocks
were of igneous origin.' _Lyell's Principles of Geology_, London,
1853, p. 51. To this I may add, that he wrote his work without
having examined granite. He says (_Theory of the Earth_, vol. i.
p. 214), 'It is true, I met with it on my return by the east
coast, when I just saw it, and no more, at Peterhead and Aberdeen;
but that was all the granite I had ever seen when I wrote my
_Theory of the Earth_. I have, since that time, seen it in
different places; because I went on purpose to examine it, as I
shall have occasion to describe in the course of this work.'
Hutton's theory of granite is noticed in _Bakewell's Geology_,
London, 1838, p. 101: but Mr. Bakewell does not seem to be aware
that the theory was formed before the observations were made.

[796] _Huttonian Theory_, in _Playfair_, vol. i. pp. 38-40, 509, 510.
Compare _Playfair's Life of Hutton_, p. 61.

[797] Hence, the objections of Kirwan were invalid; because his argument
against Hutton was 'grounded on experiments, where that very
separation of the volatile and fixed parts takes place, which it
excluded in that hypothesis of subterraneous heat.' HUTTONIAN
THEORY, in _Playfair_, vol. i. p. 193, Edinb. 1822.

[798] Hutton says (_Theory of the Earth_, Edinb. 1795, vol. i. p. 94),
'The place of mineral operations is not on the surface of the
earth; and we are not to limit nature with our imbecility, or
estimate the powers of nature by the measure of our own.' See also
p. 159, 'mineral operations proper to the lower regions of the
earth.' And p. 527, 'The mineral operations of nature lie in a
part of the globe which is necessarily inaccessible to man, and
where the powers of nature act under very different conditions
from those which we find take place in the only situation where we
can live.' Again, in vol. ii. p. 97, 'The present Theory of the
Earth holds for principle that the strata are consolidated in the
mineral regions far beyond the reach of human observation.'
Similarly, vol. ii. p. 484, 'we judge not of the progress of
things from the actual operations of the surface.'

[799] Hutton, however, did not believe that this could be done. 'In the
Theory of the Earth which was published, I was anxious to warn the
reader against the notion that subterraneous heat and fusion could
be compared with that which we induce by our chemical operations
on mineral substances here upon the surface of the earth.'
_Hutton's Theory of the Earth_, vol. i. p. 251.

[800] See, in the _Life of Hutton_, in _Playfair's Works_, vol. iv.
p. 62 note, a curious remark on his indifference to experimental
verification. Innumerable passages in his work indicate this
tendency, and show his desire to reason immediately from general
principles. Thus, in vol. i. p. 17, 'Let us strictly examine our
principles in order to avoid fallacy in our reasoning.' ... 'We
are now, in reasoning from principles, come to a point decisive of
the question.' vol. i. p. 177. 'Let us now reason from our
principles.' vol. ii. p. 308. Hence, his constantly expressed
contempt for experience; as in vol. ii. p. 367, where he says that
we must 'overcome those prejudices which contracted views of
nature and _magnified opinions of the experience of man_ may have
begotten.'

[801] Playfair (_Life of Hutton_, p. 64) says that it drew 'their
attention' (_i.e._ the attention of 'men of science'), 'very
slowly, so that several years elapsed before any one showed
himself publicly concerned about it, either as an enemy or a
friend.' He adds, as one of the reasons of this, that it contained
'too little detail of facts for a system which involved so much
that was new, and opposite to the opinions generally received.'

[802] The account of these experiments was read before the Royal Society
of Edinburgh in 1805, and is printed in their _Transactions_, vol.
vi. pp. 71-185, Edinb. 1812, 4to. The general result was (pp. 148,
149), 'That a pressure of 52 atmospheres, or 1700 feet of sea, is
capable of forming a limestone in a proper heat; That under 86
atmospheres, answering nearly to 3000 feet, or about half a mile,
a complete marble may be formed; and lastly, That, with a pressure
of 173 atmospheres, or 5700 feet, that is little more than one
mile of sea, the carbonate of lime is made to undergo complete
fusion, and to act powerfully on other earths.' See also p. 160:
'The carbonic acid of limestone cannot be constrained in heat by a
pressure less than that of 1708 feet of sea.' There is a short,
and not very accurate, notice of these instructive experiments in
_Bakewell's Geology_, London, 1838, pp. 249, 250.

[803] As Sir James Hall says, 'The truth of the most doubtful principle
which Dr. Hutton has assumed, has thus been established by direct
experiment.' _Transactions of the Royal Society of Edinburgh_,
vol. vi. p. 175.

[804] See the remarks of Sir James Hall, in _Transactions_, vol. vi.
pp. 74, 75. He observes that Hutton's 'system, however, involves
so many suppositions, apparently in contradiction to common
experience, which meet us on the very threshold, that most men
have hitherto been deterred from an investigation of its
principles, and only a few individuals have justly appreciated its
merits.' ... 'I conceived that the chemical effects ascribed by
him to compression, ought, in the first place, to be
investigated.' ... 'It occurred to me that this principle was
susceptible of being established in a direct manner by experiment,
and _I urged him to make the attempt; but he always rejected this
proposal_, on account of the immensity of the natural agents,
whose operation he supposed to lie far beyond the reach of our
imitation; and he seemed to imagine that any such attempt must
undoubtedly fail, and thus _throw discredit on opinions, already
sufficiently established, as he conceived, on other principles_.'

I have now given an account of all the most important discoveries made by Scotland, in the eighteenth century, respecting the laws of the inorganic world. I have said nothing of Watt, because, although the steam-engine, which we owe to him, is of incalculable importance, it is not a discovery, but an invention. An invention it may justly be termed, rather than an improvement.[805] Notwithstanding what had been effected in the seventeenth century, by De Caus, Worcester, Papin, and Savery, and notwithstanding the later additions of Newcomen and others, the real originality of Watt is unimpeachable. His engine was, essentially, a new invention; but, under its scientific aspect, it was merely a skilful adaptation of laws previously known; and one of its most important points, namely, the economy of heat, was a practical application of ideas promulgated by Black.[806] The only discovery made by Watt, was that of the composition of water. Though his claims are disputed by the friends of Cavendish, it would appear that he was the first who ascertained that water, instead of being an element, is a compound of two gases.[807] This discovery was a considerable step in the history of chemical analysis, but it neither involved nor suggested any new law of nature, and has, therefore, no claim to mark an epoch in the history of the human mind.[808] There is, however, one circumstance connected with it which is too characteristic to be passed over in silence. The discovery was made in 1783, by Watt, the Scotchman, and by Cavendish, the Englishman, neither of whom seems to have been aware of what the other was doing.[809] But between the two there was this difference. Watt, for several years previously, had been speculating on the subject of water in connexion with air, and having, by Black's law of latent heat, associated them together, he was prepared to believe that one is convertible into the other.[810] The idea of an intimate analogy between the two bodies having once entered his mind, gradually ripened; and when he, at last, completed the discovery, it was merely by reasoning from data which others possessed besides himself. Instead of bringing to light new facts, he drew new conclusions from former ideas.[811] Cavendish, on the other hand, obtained his result by the method natural to an Englishman. He did not venture to draw a fresh inference, until he had first ascertained some fresh facts. Indeed, his discovery was so completely an induction from his own experiments, that he omitted to take into consideration the theory of latent heat, from which Watt had reasoned, and where that eminent Scotchman had found the premisses of his argument.[812] Both of these great inquirers arrived at truth, but each accomplished his journey by a different path. And this antithesis is accurately expressed by one of the most celebrated of living chemists, who, in his remarks on the composition of water, truly says, that while Cavendish established the facts, Watt established the idea.[813]

[805] It may be traced back, certainly to the beginning of the
seventeenth century, and probably still higher. Yet the popular
opinion seems to be correct, that Watt was its real inventor;
though, of course, he could not have done what he did, without his
predecessors. This, however, may be said of all the most eminent
and successful men, as well as of the most ordinary men.

[806] On the obligations of Watt to Black, compare _Brougham's Life of
Watt_ (_Brougham's Works_, vol. i. pp. 25, 36-38, edit. Glasgow,
1855), with _Muirhead's Life of Watt_, second edit. London, 1859,
pp. 66, 83. At p. 301, Mr. Muirhead says of Watt, that 'his
principal inventions connected with the steam-engine, with all
their prodigious results, were founded, as we have seen, on the
attentive observation of great philosophical truths; and the
economy of fuel, increase of productive power, and saving of
animal labour, which gradually ensued, all originated in the
sagacious and careful thought with which he investigated the
nature and properties of heat.' But whatever investigations Watt
made into heat, he discovered no new law respecting it, or, at all
events, no new law which is large enough to be noted in the
history of thermotics, considered purely as a science, and apart
from practical application. Mr. Muirhead, in his interesting work
which I have just quoted, has published (pp. 484-486) some remarks
made on the subject by Watt, several years after the death of
Black, which, though perfectly fair and candid, show that Watt had
a rather confused notion of the real difference between an
invention and a discovery.

[807] Mr. Muirhead, in his _Life of Watt_, pp. 301-370, seems to have
put the priority of Watt beyond further doubt; though he is
somewhat hard upon Cavendish, who, there can be little question,
made the discovery for himself.

[808] I would not wish to diminish one jot of the veneration in which
the great name of Watt is justly held. But when I find the opinion
of Dr. Withering, the botanist, quoted, to the effect that his
'abilities and acquirements placed him next, if not superior, to
Newton.' (_Muirhead's Life of Watt_, p. 302), I cannot but protest
against such indiscriminate eulogy, which would rank Watt in the
same class as one of those godlike intellects of which the whole
world has not produced a score, and which are entitled to be
termed inspired, if ever human being was so. Another instance of
this injudicious panegyric will be found in the same otherwise
excellent work (_Muirhead_, pp. 324, 325), where we read that
Watt's discovery that water consists of oxygen and hydrogen, was
'the commencement of a new era, the dawn of a new day in physical
inquiry, the real foundation of the new system of chemistry; nay,
even a discovery "perhaps of greater importance than any single
fact which human ingenuity has ascertained either before or
since."'

[809] That there was no plagiarism on the part of Watt, we know from
positive evidence; that there was none on the part of Cavendish,
may be fairly presumed, both from the character of the man, and
also from the fact that in the then state of chemical knowledge
the discovery was imminent, and could not have been long delayed.
It was antecedently probable that the composition of water would
be ascertained by different persons at the same time, as we have
seen in many other discoveries which have been simultaneously
made, when the human mind, in that particular department of
inquiry, had reached a certain point. We are too apt to suspect
philosophers of stealing from each other, what their own abilities
are sufficient to work out for themselves. It is, however, certain
that Watt thought himself ill-treated by Cavendish. See _Watt's
Correspondence on the Composition of Water_, London, 1846,
pp. 48, 61.

[810] On 26th November 1783, he writes: 'For many years I have
entertained an opinion that air was a modification of water; which
was originally founded on the facts, that in most cases where air
was actually made, which should be distinguished from those
wherein it is only extricated from substances containing it in
their pores, or otherwise united to them in the state of air, the
substances were such as were known to contain water as one of
their constituent parts, yet no water was obtained in the
processes, except what was known to be only loosely connected with
them, such as the water of the crystallization of salts. _This
opinion arose from a discovery that the latent heat contained in
steam diminished, in proportion as the sensible heat of the water
from which it was produced, increased_; or, in other words, that
the latent heat of steam was less when it was produced under a
greater pressure, or in a more dense state, and greater when it
was produced under a less pressure, or in a less dense state;
which led me to conclude, that when a very great degree of heat
was necessary for the production of the steam, the latent heat
would be wholly changed into sensible heat; and that, in such
cases, the steam itself might suffer some remarkable change. I now
abandon this opinion, in so far as relates to the change of water
into air, as I think that may be accounted for on better
principles.' See this remarkable passage, which is quite decisive
as to the real history of Watt's discovery, in _Correspondence of
James Watt on the Composition of Water_, London, 1846, pp. 84, 85.
Compare p. cxxiv. and p. 248 note.

[811] In the paper which he communicated to the Royal Society, announcing
his discovery, he, well knowing the empirical character of the
English mind, apologizes for this; and says, 'I feel much
reluctance to lay my thoughts on these subjects before the public
in their present indigested state, and _without having been able
to bring them to the test of such experiments as would confirm or
refute them_.' _Watt's Correspondence on the Discovery of the
Composition of Water_, pp. 77, 78. Eleven months earlier, that is
in December 1782, he writes (_Ibid._ p. 4): 'Dr. Priestley has
made a most surprising discovery, which _seems to confirm my
theory_ of water's undergoing some very remarkable change at the
point where all its latent heat would be changed into sensible
heat.'

[812] 'He' (_i.e._ Cavendish) 'here omits entirely the consideration of
latent heat; an omission which he even attempts to justify, in one
of the passages interpolated by Blagden. But it is well known to
every one acquainted with the first principles of chemical
science, even as it was taught in the days of Black, and it was
indisputably familiar to Mr. Watt, that no aëriform fluid can be
converted into a liquid, nor any liquid into a solid, without tho
evolution of heat, previously latent. This essential part of the
process, Mr. Cavendish's theory does not embrace; but without it,
no theory on the subject can be complete; and it will presently be
seen, that Mr. Watt took it fully into account.' _Muirhead's Life
of Watt_, p. 315.

[813] 'Cavendish and Watt both discovered the composition of water.
Cavendish established the facts; Watt the idea.' ... '_The
attaching too high a value to the mere facts, is often a sign of a
want of ideas._' _Liebig's Letters on Chemistry_, London, 1851, p.
48. The last sentence of this illustrious philosopher, which I
have put in italics, should be well pondered in England. If I had
my way, it should be engraved in letters of gold over the portals
of the Royal Society and of the Royal Institution.

Thus much, as to what was effected by the Scotch in the department of inorganic science. If we now turn to organic science, we shall find that, there also, their labours were very remarkable. To those who are capable of a certain elevation and compass of thought, it will appear, in the highest degree, probable, that, between the organic and inorganic world, there is no real difference. That they are separated, as is commonly asserted, by a sharp line of demarcation, which indicates where one abruptly ends, and the other abruptly begins, seems to be a supposition altogether untenable. Nature does not pause, and break off in this fitful and irregular manner. In her works there is neither gap nor chasm. To a really scientific mind, the material world presents one vast and uninterrupted series, gradually rising from the lowest to the highest forms, but never stopping. In one part of that series, we find a particular structure, which, so far as our observations have yet extended, we, in another part, cannot find. We also observe particular functions, which correspond to the structure, and, as we believe, result from it. This is all we know. Yet, from these scanty facts, we, who, at present, are still in the infancy of knowledge, and have but skimmed the surface of things, are expected to infer, that there must be a point, in the chain of existence, where both structure and function suddenly cease, and, after which, we may vainly search for signs of life. It would be difficult to conceive a conclusion more repugnant to the whole march and analogy of modern thought. In every department, the speculations of the greatest thinkers are constantly tending to coördinate all phenomena, and to regard them as different, indeed, in degree, but by no means as different in kind. Formerly, men were content to ground their conviction of this difference in kind, on the evidence of the eye, which, on a cursory inspection, saw an organization in some bodies, and not in others. From the organization, they inferred the life, and supposed that plants, for instance, had life, but that minerals had none. This sort of argument was long deemed satisfactory; but, in the course of time, it broke down; more evidence was required, and, since the middle of the seventeenth century, it has been universally admitted, that the eye, by itself, is an untrustworthy witness, and that we must employ the microscope, instead of relying on the unaided testimony of our own puny and precarious senses. But the microscope is steadily improving, and we cannot tell what limits there are to its capacity for improvement. Consequently, we cannot tell what fresh secrets it may disclose. Neither can we say, that it may not be altogether superseded by some new artificial resource, which shall furnish us with evidence, as superior to any yet supplied, as our present evidence is superior to that of the naked eye. Even already, and notwithstanding the shortness of time during which the microscope has been a really effective instrument, it has revealed to us organizations, the existence of which no one had previously suspected. It has proved, that what, for thousands of years, had been deemed mere specks of inert matter, are, in truth, animals possessing most of the functions which we possess, reproducing their species in regular and orderly succession, and endowed with a nervous system, which shows that they must be susceptible of pain and enjoyment. It has detected life hidden in the glaciers of Switzerland; it has found it embedded in the polar ice, and, if it can flourish there, it is hard to say from what quarter it can be shut out. So unwilling, however, are most men to relinquish old notions, that the resources of chemistry have been called in, to ascertain the supposed difference between organic and inorganic matter: it being asserted, that, in the organic world, there is a greater complexity of molecular combination, than in the inorganic.[814] Chemists further assert, that, in organic nature, there is a predominance of carbon, and, in inorganic, a predominance of silicon.[815] But chemical analysis, like microscopic observation, is making such rapid strides, that each generation, I had almost said each year, is unsettling some of the conclusions previously established; so that, now, and for a long time hence, we must regard those conclusions as empirical, and, indeed, as merely tentative. Surely a permanent and universal inference cannot be drawn from shifting and precarious facts, which are admitted to-day, and may be overthrown to-morrow. It would, therefore, appear that, in favour of the opinion, that some bodies are living, and that others are dead, we have nothing, except the circumstance, that our researches, so far as they have yet gone, have shown that cellular structure, growth, and reproduction, are not the invariable properties of matter, but are excluded from a large part of the visible world, which, on that account, we call inanimate. This is the whole of the argument on that side of the question. On the other side, we have the fact, that our sight, and the artificial instruments, by whose aid we have arrived at this conclusion, are confessedly imperfect; and we have the further fact, that, imperfect as they are, they have proved, that the organic kingdom is infinitely more extensive than the boldest dreamer had ever imagined, while they have not been able to enlarge the boundaries of the inorganic kingdom to any thing like the same amount. This shows, that, so far as our opinions are concerned, the balance is steadily inclining in one given direction; in other words, as our knowledge advances, a belief in the organic is encroaching upon a belief in the inorganic.[816] When we, moreover, add, that all science is manifestly converging towards one simple and general theory, which shall cover the whole range of material phenomena, and that, at each successive step, some irregularities are explained away, and some inequalities are reduced, it can hardly be doubted, that such a movement tends to weaken those old distinctions, the reality of which has been too hastily assumed; and that, in their place, we must, sooner or later, substitute the more comprehensive view, that life is a property of all matter, and that the classification of bodies into animate and inanimate, or into organic and inorganic, is merely a provisional arrangement, convenient, perhaps, for our present purposes, but which, like all similar divisions, will eventually be merged in a higher and wider scheme.

[814] 'Organic substances, whether directly derived from the vegetable
or animal kingdom, or produced by the subsequent modification of
bodies which thus originate, are remarkable as a class for a
degree of complexity of constitution far exceeding that observed
in any of the compounds yet described.' _Fownes' Chemistry_, 3rd
edit., London, 1850, p. 353. I quote this, as the first authority
at hand, for a doctrine which is universally admitted by chemists,
and which is indubitably true, _so far as our experiments have at
present extended_.

[815] 'As the organic world is characterized by the predominance, in
quantity, of carbon, so the mineral or inorganic world is marked
by a similar predominance of silicon.' _Turner's Chemistry_,
edited by Liebig and Gregory, vol. ii. p. 678, London, 1847.

[816] I mean, of course, to apply this remark only to the globe we
inhabit, and not to extra-terrestrial phenomena. Respecting the
organization or non-organization of what exists out of this earth,
we have no evidence, and can hardly expect to have any for
centuries. Inferences have, indeed, been drawn from telescopic
observations; and attempts are now being made, abroad, to
determine, by a still more refined process, the physical
composition of some of the heavenly bodies. But without venturing,
in this note, to enter into such discussions, or even to state
their purport, I may say, that the difficulty of _verification_
will long prove an insuperable barrier to our knowledge of the
truth or falsehood of any results which may be obtained.

Until, however, that step is taken, we must be content to reason according to the evidence supplied by our imperfect instruments, or by our still more imperfect senses. We, therefore, recognize the difference between organic and inorganic nature, not as a scientific truth, but as a scientific artifice, by which we separate in idea, what is inseparable in fact; hoping, in this way, to pursue our course with the greater ease, and ultimately to obtain results, which will make the artifice needless. Assuming, then, this division, we may refer all investigations of organic bodies to one of two objects. The first object is, to ascertain the law of those bodies, in their usual, healthy, or, as we somewhat erroneously phrase it, normal course. The other object is, to ascertain their law, in their unusual, unhealthy, or abnormal course. When we attempt to do the first of these things, we are physiologists. When we attempt to do the second, we are pathologists.[817]

[817] Mr. Simon, in his thoughtful and suggestive Lectures, says, 'We
may describe Pathology to consist in the Science of Life under
other conditions than those of ideal perfection.' _Simon's
Lectures on Pathology_, London, 1850, p. 14. This is by far the
best description I have met with; though, as it involves a
negative, it cannot be accepted as a definition. Indeed, the
context shows that Mr. Simon does not suppose it to be one.

Physiology and pathology are thus the two fundamental divisions of all organic science.[818] Each is intimately connected with the other; and eventually, no doubt, both will be fused into a single study, by discovering laws which will prove that here, as elsewhere, nothing is really abnormal, or irregular. Hitherto, however, the physiologists have immeasurably outstripped the pathologists in the comprehensiveness of their views, and, therefore, in the value of their results. For, the best physiologists distinctly recognize that the basis of their science must include, not only the animals below man, but also the entire vegetable kingdom, and that, without this commanding survey of the whole realm of organic nature, we cannot possibly understand even human physiology, still less general physiology. The pathologists, on the other hand, are so much in arrear, that the diseases of the lower animals rarely form part of their plan; while the diseases of plants are almost entirely neglected, although it is certain that, until all these have been studied, and some steps taken to generalize them, every pathological conclusion will be eminently empirical, on account of the narrowness of the field from which it is collected.