Fragments of Science: a Series of Detached Essays, Addresses, and Reviews. V. 1-2

Part 1

Produced by Jon Richfield

FRAGMENTS OF SCIENCE:

A Series of Detached

ESSAYS, ADDRESSES, AND REVIEWS.

JOHN TYNDALL, F.R.S.

Printed By Spottiswoode AND CO.

NEW-STREET SQUARE

PARLIAMENT STREET

SIXTH EDITION,

VOL. 1.

LONDON: LONGMANS, GREEN, AND CO.

1879.

All rights reserved.

PREFACE TO THE SIXTH EDITION.

VOL. I. INORGANIC NATURE.

I. THE CONSTITUTION OF NATURE.

II. RADIATION.

1. Visible and Invisible Radiation.

2. Origin and Character of Radiation. The Aether.

3. The Atomic Theory in reference to the Aether.

4. Absorption of Radiant Heat by Gases.

5. Formation of Invisible Foci.

6. Visible and Invisible Rays of the Electric Light.

Figure 1 Spectrum of Electric Light.

7. Combustion by Invisible Rays.

8. Transmutation of Rays: Calorescence.

9. Deadness of the Optic Nerve to the Calorific Rays.

10. Persistence of Rays.

Part 2

11. Absorption of Radiant Heat by Vapours and Odours.

12. Aqueous Vapour in relation to the Terrestrial Temperatures.

13. Liquids and their Vapours in relation to Radiant Heat.

14. Reciprocity of Radiation and Absorption.

15. Influence of Vibrating Period and Molecular Form.

Physical Analysis of the Human Breath.

16. Summary and Conclusion.

III. ON RADIANT HEAT IN RELATION TO THE COLOUR AND CHEMICAL CONSTITUTION OF BODIES.

IV. NEW CHEMICAL REACTIONS PRODUCED BY LIGHT.

1. DECOMPOSITION BY LIGHT.

Physical Considerations.

Production of Sky-blue by the Decomposition of Nitrite of Amyl.

2. ON THE BLUE COLOUR OF THE SKY, & THE POLARISATION OF SKYLIGHT.

3. THE SKY OF THE ALPS.

V. ON DUST AND DISEASE.

Experiments on Dusty Air.

The Germ Theory of Contagious Disease.

Parasitic Diseases of Silkworms. Pasteur's Researches.

Origin and Propagation of Contagious Matter.

The Germ Theory applied to Surgery.

The Luminous beam as a means of Research.

The Floating Matter of the Air.

Dr. Bennett's Experiments.

Application of Luminous beams to Water.

Chalk-water. Clark's Softening Process.

Cotton-wool Respirator.

Fireman's Respirator.

Helmholtz on Hay Fever.

Part 3

VI. VOYAGE TO ALGERIA TO OBSERVE THE ECLIPSE.

VII. NIAGARA.

VIII THE PARALLEL ROADS OF GLEN ROY.

IX. ALPINE SCULPTURE.

X. RECENT EXPERIMENTS ON FOG-SIGNALS.

XI. ON THE STUDY OF PHYSICS.

XII. ON CRYSTALLINE AND SLATY CLEAVAGE.

XIII. ON PARAMAGNETIC AND DIAMAGNETIC FORCES.

XIV. PHYSICAL BASIS OF SOLAR CHEMISTRY.

XV. ELEMENTARY MAGNETISM.

XVI. ON FORCE.

XVII. CONTRIBUTIONS TO MOLECULAR PHYSICS.

XVIII. LIFE, AND LETTERS OF FARADAY.

XIX. THE COPLEY MEDALIST OF 1870.

XX. THE COPLEY MEDALIST OF 1871.

XXI. DEATH BY LIGHTNING.

XXII. SCIENCE AND THE 'SPIRITS'.

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VOL. II.

I. REFLECTIONS ON PRAYER AND NATURAL LAW.

II MIRACLES AND SPECIAL PROVIDENCES.

ADDITIONAL REMARKS ON MIRACLES.

III ON PRAYER AS A FORM OF PHYSICAL ENERGY.

IV. VITALITY.

V. MATTER AND FORCE.

VI. SCIENTIFIC MATERIALISM.

VII. AN ADDRESS TO STUDENTS.

VIII. SCIENTIFIC USE OF THE IMAGINATION.

Part 4

IX. THE BELFAST ADDRESS.

X. APOLOGY FOR THE BELFAST ADDRESS.

XI. THE REV. JAMES MARTINEAU AND THE BELFAST ADDRESS.

XII. FERMENTATION, & ITS BEARINGS ON SURGERY & MEDICINE.

XIII. SPONTANEOUS GENERATION.

XIV. SCIENCE AND MAN.

XV. PROFESSOR VIRCHOW AND EVOLUTION.

XVI. THE ELECTRIC LIGHT.

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PREFACE TO THE SIXTH EDITION.

TO AVOID unwieldiness of bulk this edition of the 'Fragments' is published in two volumes, instead of, as heretofore, in one.

The first volume deals almost exclusively with the laws and phenomena of matter. The second trenches upon questions in which the phenomena of matter interlace more or less with those of mind.

New Essays have been added, while old ones have been revised, and in part recast. To be clear, without being superficial, has been my aim throughout.

In neither volume have I aspired to sit in the seat of the scornful, but rather to treat the questions touched upon with a tolerance, if not a reverence, befitting their difficulty and weight.

Holding, as I do, the nebular hypothesis, I am logically bound to deduce the life of the world from forces inherent in the nebula. With this view, which is set forth in the second volume, it seemed but fair to associate the reasons which cause me to conclude that every attempt made in our day to generate life independently of antecedent life has utterly broken down.

A discourse on the Electric Light winds up the Second volume. The incongruity of its position is to be referred to the lateness of its delivery.

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VOL. I. INORGANIC NATURE.

I. THE CONSTITUTION OF NATURE.

WE cannot think of space as finite, for wherever in imagination we erect a boundary, we are compelled to think of space as existing beyond it. Thus by the incessant dissolution of limits we arrive at a more or less adequate idea of the infinity of space. But, though compelled to think of space as unbounded, there is no mental necessity compelling us to think of it either as filled or empty; whether it is so or not must be decided by experiment and observation. That it is not entirely void, the starry heavens declare; but the question still remains, Are the stars themselves hung in vacuo? Are the vast regions which surround them, and across which their light is propagated, absolutely empty? A century ago the answer to this question, founded on the Newtonian theory, would have been, 'No, for particles of light are incessantly shot through space.' The reply of modern science is also negative, but on different grounds. It has the best possible reasons for rejecting the idea of luminiferous particles; but, in support of the conclusion that the celestial spaces are occupied by matter, it is able to offer proofs almost as cogent as those which can be adduced of the existence of an atmosphere round the earth. Men's minds, indeed, rose to a conception of the celestial and universal atmosphere through the study of the terrestrial and local one. From the phenomena of sound, as displayed in the air, they ascended to the phenomena of light, as displayed in the aether; which is the name given to the interstellar medium.

The notion of this medium must not be considered as a vague or fanciful conception on the part of scientific men. Of its reality most of them are as convinced as they are of the existence of the sun and moon. The luminiferous aether has definite mechanical properties. It is almost infinitely more attenuated than any known gas, but its properties are those of a solid rather than of a gas. It resembles jelly rather than air. This was not the first conception of the aether, but it is that forced upon us by a more complete knowledge of its phenomena. A body thus constituted may have its boundaries; but, although the aether may not be co-extensive with space, it must at all events extend as far as the most distant visible stars. In fact it is the vehicle of their light, and without it they could not be seen. This all-pervading substance takes up their molecular tremors, and conveys them with inconceivable rapidity to our organs of vision. It is the transported shiver of bodies countless millions of miles distant, which translates itself in human consciousness into the splendour of the firmament at night.

If the aether have a boundary, masses of ponderable matter might be conceived to exist beyond it, but they could emit no light. Beyond the aether dark suns might burn; there, under proper conditions, combustion might be carried on; fuel might consume unseen, and metals be fused in invisible fires. A body, moreover, once heated there, would continue for ever heated; a sun or planet once molten, would continue for ever molten. For, the loss of heat being simply the abstraction of molecular motion by the aether, where this medium is absent no cooling could occur. A sentient being on approaching a heated body in this region, would be conscious of no augmentation of temperature. The gradations of warmth dependent on the laws of radiation would not exist, and actual contact would first reveal the heat of an extra ethereal sun.

Imagine a paddle-wheel placed in water and caused to rotate. From it, as a centre, waves would issue in all directions, and a wader as he approached the place of disturbance would be met by stronger and stronger waves. This gradual augmentation of the impression made upon the wader is exactly analogous to the augmentation of light when we approach a luminous source. In the one case, however, the coarse common nerves of the body suffice; for the other we must have the finer optic nerve. But suppose the water withdrawn; the action at a distance would then cease, and, as far as the sense of touch is concerned, the wader would be first rendered conscious of the motion of the wheel by the blow of the paddles. The transference of motion from the paddles to the water is mechanically similar to the transference of molecular motion from the heated body to the aether; and the propagation of waves through the liquid is mechanically similar to the propagation of light and radiant heat.

As far as our knowledge of space extends, we are to conceive it as the holder of the luminiferous aether, through which are interspersed, at enormous distances apart, the ponderous nuclei of the stars. Associated with the star that most concerns us we have a group of dark planetary masses revolving at various distances round it, each again rotating on its own axis; and, finally, associated with some of these planets we have dark bodies of minor note--the moons. Whether the other fixed stars have similar planetary companions or not is to us a matter of pure conjecture, which may or may not enter into our conception of the universe. But probably every thoughtful person believes, with regard to those distant suns, that there is, in space, something besides our system on which they shine.

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