The constitution of the Sun as revealed by the spectroscope.

Principles of spectroscopic analysis

Effect of increasing prismatic dispersion

Browning's automatic spectroscope

Direct vision prisms

The author's plan for a double automatic battery

The spectroscopic analysis of the Sun's disc

the prominences themselves. 145

How the spectroscope exhibits motions of approach or recess

The method very readily applicable in solar spectroscopy

Interpretation of peculiarities in the prominence-lines.

Summary

146

151

154

156

Work of Galileo and Scheiner (and note from Burton's Anatomy

Dr. Wilson's observations and theory

Observations of Sir William Herschel.

His study of the faculæ

The solar corrugations and nodules

Sir William Herschel's theories respecting the Sun

Sir John Herschel's theory respecting them.

Schwabe's discovery of the periodicity of spot-frequency

Associated period of magnetic disturbance

Solar outburst witnessed by Carrington and Hodgson

Followed by magnetic disturbances

Carrington's researches

Proper motion of the spots.

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Relative position of spots and faculæ

215

General results as to umbræ, penumbræ, and faculæ .

216

Faye and others ascribe them to illusion, &c.

The prominences seen during the eclipse of 1851

Still ascribed to illusion

The eclipse of 1860-Goldschmidt's observations.

Photographs taken by De la Rue and Secchi

Conclusions arrived at by Secchi

Recognition of the chromosphere

Probable distribution of the prominences

The vast dimensions of some of them.

The eclipse of August 1868.

Tennant's photographs

Other views of the prominences

Spectroscopic analysis of the prominences.

They are shown to be gaseous

Janssen sees the prominence-lines when Sun is not eclipsed.

Lockyer does the like, later but independently

Study of the prominence-spectrum

Secchi's results (foot-note).

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243

Lockyer re-discovers chromosphere and (unaware of its prior re-

cognition) gives it a name

His account of the views of others respecting the chromosphere

(foot-note)

The chromosphere probably not a true solar atmosphere
Low atmospheric pressure near the photosphere

Solar storms-their exceeding violence

Observations by Professor Young, of America

Dr. Huggins succeeds in seeing the prominences themselves.

Observations by Lockyer on Huggins's plan

Dr. Zöllner's observations

Respighi's daily views of the prominences and chromosphere

His account of the phenomena they present

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The eclipse of August 1869

Professor Young photographs a prominence when the Sun is not

eclipsed.

312

CHAPTER VI.

THE CORONA AND ZODIACAL LIGHT.

Discovery of the corona

Observations by Clavius, Kepler, and Wyberd

The phenomena seen at commencement of totality explained

Observations by Plantade, Capiés, and Maraldi

The eclipses of 1733, 1766, and 1778 .

Observations made by Airy, Baily, and others in 1842.

Peculiar structure of the corona

The eclipses of 1851, 1858, and 1860

In 1860 Secchi photographs the corona

Eclipses of April 1865 and March 1867

a

Observations by Grosch and Vidal in August 1867

The corona during the eclipse of August, 1868

Tennant observes its spectrum to be continuous
Seemingly discordant results obtained in August 1869
An attempt to reconcile these results

Direct observations of the corona in August 1869

Mr. Gilman's observations

Professor Newcombe's

Professor Eastman's

Mr. Homer Laue's

General Myer's

The corona successfully photographed in August 1869
Discarded theories of the corona.

The Atmospheric-glare theory considered and disproved
The corona not a solar atmosphere

Its structure perhaps meteoric and cometic

Association between coronal, auroral, and cometic phenomena

Further evidence deduced from the Zodiacal Light

This radiance certainly not terrestrial .

Summary of the evidence

CHAPTER VII.

PHYSICAL CONDITION OF THE SUN.

Great difficulty of the subject

379

380

381

.

384

385

The elements exist in the Sun in conditions we are not familiar with

We are as yet but imperfectly acquainted with physical laws

Amazing velocity with which matter is moving in the Sun

General consideration of the Sun's constitution

Variations in the condition of the solar elements at different levels 386

Evidence given by the spectroscope imperfect

387

Does the outline of the Sun's disc indicate his real dimensions?

The solar spots present many perplexing problems

We cannot as yet tell whether they are due to internal or external

action

$90

The origin of the prominences still a mystery

The corona's true nature also unknown

392

392

CHAPTER VIII.

THE SUN-OUR FIRE, LIGHT, AND LIFE.

Extent of the Sun's influence on the Earth .

Sir John Herschel's account of the Sun's action

His and Pouillet's measurements of the Sun's heat

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The Sun's light.

397

Action of the Sun on vegetation

Duty of scientific men in this matter

The Sun's chemical activity.

Eventual exhaustion of the Earth's 'force-principal'

The direct utilisation of solar energies

The enormous 'force-income' which may thus become available

These ideas extended to other worlds than ours

Source of the solar energy

The Meteoric theory and the theory of Helmholtz

Conclusion-reflections of Professor Tyndall

CHAPTER IX.

THE SUN AMONG HIS PEERS.

The Sun in the sidereal system

407

409

410

Distances of the stars

Structure of the sidereal system

Sir W. Herschel's star-gauging

Signs of aggregation among lucid stars

The lucid stars crowd along Milky Way

Distribution of the nebulæ .

Milky Way probably a spiral system of small stars

Sun travelling in space from a rich region in the Southern to

another in the Northern heavens

Dissimilar helicoidal paths of the planets

Has the Sun companion-suns in his voyage through space?

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430

433

434

436

440

441