25 chapters
8 hour read
Selected Chapters
25 chapters
Preliminary discourse on the Study of NATURAL PHILOSOPHY
Preliminary discourse on the Study of NATURAL PHILOSOPHY
BY SIR JOHN F. W. HERSCHEL, BART. K.H. M.A.—D.C.L.—F.R.S.L&E.—M.R.I.A.—F.R.A.S. F.G.S.—M.C.U.P.S.—&c. &c. NEW EDITION. 1851. NATURÆ MINISTER ET INTERPRES. NEW EDITION. London: PRINTED FOR LONGMAN, BROWN, GREEN & LONGMANS, PATERNOSTER ROW...
16 minute read
Read Chapter
Read Chapter
CHAPTER I.
CHAPTER I.
OF MAN REGARDED AS A CREATURE OF INSTINCT, OF REASON, AND SPECULATION.—GENERAL INFLUENCE OF SCIENTIFIC PURSUITS ON THE MIND. (1.) T he situation of man on the globe he inhabits, and over which he has obtained the control, is in many respects exceedingly remarkable. Compared with its other denizens, he seems, if we regard only his physical constitution, in almost every respect their inferior, and equally unprovided for the supply of his natural wants and his defence against the innumerable enemie
18 minute read
Read Chapter
Read Chapter
CHAP. II.
CHAP. II.
OF ABSTRACT SCIENCE AS A PREPARATION FOR THE STUDY OF PHYSICS.—A PROFOUND ACQUAINTANCE WITH IT NOT INDISPENSABLE FOR A CLEAR UNDERSTANDING OF PHYSICAL LAWS.—HOW A CONVICTION OF THEIR TRUTH MAY BE OBTAINED WITHOUT IT.—INSTANCES.—FURTHER DIVISION OF THE SUBJECT. (13.) S cience is the knowledge of many, orderly and methodically digested and arranged, so as to become attainable by one. The knowledge of reasons and their conclusions constitutes abstract , that of causes and their effects, and of the
20 minute read
Read Chapter
Read Chapter
CHAP. III.
CHAP. III.
OF THE NATURE AND OBJECTS, IMMEDIATE AND COLLATERAL, OF PHYSICAL SCIENCE, AS REGARDED IN ITSELF, AND IN ITS APPLICATION TO THE PRACTICAL PURPOSES OF LIFE, AND ITS INFLUENCE ON THE WELL-BEING AND PROGRESS OF SOCIETY. (26.) T he first thing impressed on us from our earliest infancy is, that events do not succeed one another at random, but with a certain degree of order, regularity, and connection;—some constantly, and, as we are apt to think, immutably,—as the alternation of day and night, summer
45 minute read
Read Chapter
Read Chapter
CHAPTER I.
CHAPTER I.
OF EXPERIENCE AS THE SOURCE OF OUR KNOWLEDGE.—OF THE DISMISSAL OF PREJUDICES.—OF THE EVIDENCE OF OUR SENSES. (66.) I nto abstract science, as we have before observed, the notion of cause does not enter. The truths it is conversant with are necessary ones, and exist independent of cause. There may be no such real thing as a right-lined triangle marked out in space; but the moment we conceive one in our minds, we cannot refuse to admit the sum of its three angles to be equal to two right angles; a
12 minute read
Read Chapter
Read Chapter
CHAP. II.
CHAP. II.
OF THE ANALYSIS OF PHENOMENA (76.) P henomena , then, or appearances, as the word is literally rendered, are the sensible results of processes and operations carried on among external objects, or their constituent principles, of which they are only signals, conveyed to our minds as aforesaid. Now, these processes themselves may be in many instances rendered sensible ; that is to say, analysed, and shown to consist in the motions or other affections of sensible objects themselves. For instance, t
22 minute read
Read Chapter
Read Chapter
CHAP. III.
CHAP. III.
OF THE STATE OF PHYSICAL SCIENCE IN GENERAL, PREVIOUS TO THE AGE OF GALILEO AND BACON. (96.) I t is to our immortal countryman Bacon that we owe the broad announcement of this grand and fertile principle; and the developement of the idea, that the whole of natural philosophy consists entirely of a series of inductive generalizations, commencing with the most circumstantially stated particulars, and carried up to universal laws, or axioms, which comprehend in their statements every subordinate de
13 minute read
Read Chapter
Read Chapter
CHAP. IV.
CHAP. IV.
OF THE OBSERVATION OF FACTS AND THE COLLECTION OF INSTANCES. (109.) N ature offers us two sorts of subjects of contemplation in the external world,—objects, and their mutual actions. But, after what has been said on the subject of sensation, the reader will be at no loss to perceive that we know nothing of the objects themselves which compose the universe, except through the medium of the impressions they excite in us, which impressions are the results of certain actions and processes in which s
18 minute read
Read Chapter
Read Chapter
CHAP. V.
CHAP. V.
OF THE CLASSIFICATION OF NATURAL OBJECTS AND PHENOMENA, AND OF NOMENCLATURE. (129.) T he number and variety of objects and relations which the observation of nature brings before us are so great as to distract the attention, unless assisted and methodized by such judicious distribution of them in classes as shall limit our view to a few at a time, or to groups so bound together by general resemblances that, for the immediate purpose for which we consider them, they may be regarded as individuals
9 minute read
Read Chapter
Read Chapter
CHAP. VI.
CHAP. VI.
OF THE FIRST STAGE OF INDUCTION.—THE DISCOVERY OF PROXIMATE CAUSES, AND LAWS OF THE LOWEST DEGREE OF GENERALITY, AND THEIR VERIFICATION. (137.) T he first thing that a philosophic mind considers, when any new phenomenon presents itself, is its explanation , or reference to an immediate producing cause. If that cannot be ascertained, the next is to generalize the phenomenon, and include it, with others analogous to it, in the expression of some law, in the hope that its consideration, in a more a
56 minute read
Read Chapter
Read Chapter
CHAP. VII.
CHAP. VII.
OF THE HIGHER DEGREES OF INDUCTIVE GENERALIZATION, AND OF THE FORMATION AND VERIFICATION OF THEORIES. (201.) A s particular inductions and laws of the first degree of generality are obtained from the consideration of individual facts, so Theories result from a consideration of these laws, and of the proximate causes brought into view in the previous process, regarded all together as constituting a new set of phenomena, the creatures of reason rather than of sense, and each representing under gen
37 minute read
Read Chapter
Read Chapter
PART III.
PART III.
OF THE SUBDIVISION OF PHYSICS INTO DISTINCT BRANCHES, AND THEIR MUTUAL RELATIONS. OF THE PHENOMENA OF FORCE, AND OF THE CONSTITUTION OF NATURAL BODIES. (232.) N atural History may be considered in two very different lights: either, 1st, as a collection of facts and objects presented by nature, from the examination, analysis, and combination of which we acquire whatever knowledge we are capable of attaining both of the order of nature, and of the agents she employs for producing her ends, and fro
3 minute read
Read Chapter
Read Chapter
Statics and Dynamics.
Statics and Dynamics.
(236.) The principles have been definitively fixed by Galileo and his successors, down to Newton, on a basis of sound induction; and as they are perfectly general, and apply to every case, they are competent, as we have already before observed, to the solution of every problem that can occur in the deductive processes, by which phenomena are to be explained, or effects calculated. Hence, they include every question that can arise respecting the motions and rest of the smallest particles of matte
5 minute read
Read Chapter
Read Chapter
Pneumatics.
Pneumatics.
(244.) Pneumatics relates to the equilibrium or movements of aërial fluids under all circumstances of pressure, density, and elasticity. The weight of the air, and its pressure on all the bodies on the earth’s surface, were quite unknown to the ancients, and only first perceived by Galileo, on the occasion of a sucking-pump refusing to draw water above a certain height. Before his time it had always been supposed that water rose by suction in a pipe, in consequence of a certain natural abhorrenc
4 minute read
Read Chapter
Read Chapter
Hydrostatics.
Hydrostatics.
(249.) The principles of the equilibrium of liquids, understanding by this word such fluids as do not, though quite at liberty, attempt to dilate themselves beyond a certain point, are at once few and simple. The first steps towards a knowledge of them were made by Archimedes, who established the general fact, that a solid immersed in a liquid loses a portion of its weight equal to that of the liquid it displaces. It seems very astonishing, after this, that it should not have been at once conclu
6 minute read
Read Chapter
Read Chapter
Nature of Solids in general.
Nature of Solids in general.
(257.) The intimate constitution of solids is, in all probability, very complicated, and we cannot be said to know much of it. By some recent delicate experiments on the dimensions of wires violently strained, it has been shown that they are to a certain small extent capable of being dilated by tension, as they are also of being compressed by pressure, but within limits even narrower than those of liquids. Usually, when strained too far, they break, and refuse to re-unite; or, if compressed too
2 minute read
Read Chapter
Read Chapter
Crystallography.
Crystallography.
(261.) It cannot be supposed that these and many other tangible qualities, as they may be called, should subsist in solids without a corresponding mechanism in their internal structure. That they have such a mechanism, and that a very curious and intricate one, the phenomena of crystallography sufficiently show. This interesting and beautiful department of natural science is of comparatively very modern date. That many natural substances affected certain forms must have been known from the earli
12 minute read
Read Chapter
Read Chapter
Light and Vision.
Light and Vision.
(273.) The nature of light has always been involved in considerable doubt and mystery. The ancients could scarcely be said to have any opinion on the subject, unless, indeed, it could be considered such to affirm that distant bodies could not be put into communication without an intermedium; and that, therefore, there must be something between the eye and the thing seen. What that something is, however, they could only form crude and vague conjectures. One supposed that the eyes themselves emit
17 minute read
Read Chapter
Read Chapter
Astronomy and Celestial Mechanics.
Astronomy and Celestial Mechanics.
(293.) A stronomy, as has been observed in the former part of this discourse, as a science of observation, had made considerable progress among the ancients: indeed, it was the only branch of physical science which could be regarded as having been cultivated by them with any degree of assiduity or real success. The Chaldean and Egyptian records had furnished materials from which the motions of the sun and moon could be calculated with sufficient exactness for the prediction of eclipses; and some
19 minute read
Read Chapter
Read Chapter
Geology.
Geology.
(313.) The researches of physical astronomy are confessedly incompetent to carry us back to the origin of our system, or to a period when its state was, in any great essential, different from what it is at present. So far as the causes now in action go, and so far as our calculations will enable us to estimate their effects, we are equally unable to perceive in the general phenomena of the planetary system either the evidence of a beginning, or the prospect of an end. Geometers, as already state
10 minute read
Read Chapter
Read Chapter
Mineralogy.
Mineralogy.
(325.) T he consideration of the history and structure of our globe, and the examination of the fossil contents of its strata, lead us naturally to consider the materials of which it consists. The history of these materials, their properties as objects of philosophical enquiry, and their application to the useful arts and the embellishments of life, with the characters by which they can be certainly distinguished one from another, form the object of mineralogy, taken in its most extended sense.
7 minute read
Read Chapter
Read Chapter
Chemistry.
Chemistry.
(332.) The laws which concern the intimate constitution of bodies, not as respects their structure or the manner in which their parts are put together, but as regards their materials or the ingredients of which those parts are composed, form the objects of chemistry. A solid body may be regarded as a fabric, more or less regularly and artificially constructed, in which the materials and the workmanship may be separately considered, and in which, though the latter be ruined and confounded by viol
15 minute read
Read Chapter
Read Chapter
Heat.
Heat.
(344.) O ne of the chief agents in chemistry, on whose proper application and management the success of a great number of its enquiries depends, and many of whose most important laws are disclosed to us by phenomena of a chemical nature, is HEAT . Although some of its effects are continually before our eyes as matters of the most common occurrence, insomuch that there is scarcely any process in the useful arts and manufactures which does not call for its intervention, and although, independent o
16 minute read
Read Chapter
Read Chapter
Magnetism and Electricity.
Magnetism and Electricity.
(363.) These two subjects, which had long maintained a distinct existence, and been studied as separate branches of science, are at length effectually blended. This is, perhaps, the most satisfactory result which the experimental sciences have ever yet attained. All the phenomena of magnetic polarity, attraction, and repulsion, have at length been resolved into one general fact, that two currents of electricity, moving in the same direction repel, and in contrary directions attract, each other.
24 minute read
Read Chapter
Read Chapter
CHAP. VI.
CHAP. VI.
OF THE CAUSES OF THE ACTUAL RAPID ADVANCE OF THE PHYSICAL SCIENCES COMPARED WITH THEIR PROGRESS AT AN EARLIER PERIOD. (383.) T here is no more extraordinary contrast than that presented by the slow progress of the physical sciences, from the earliest ages of the world to the close of the sixteenth century, and the rapid developement they have since experienced. In the former period of their history, we find only small additions to the stock of knowledge, made at long intervals of time; during wh
32 minute read
Read Chapter
Read Chapter