The constitution of the Sun as revealed by the spectroscope.

Principles of spectroscopic analysis

Effect of increasing prismatic dispersion

The author's plan for a double automatic battery

The spectroscopic analysis of the Sun's dise

How the spectroscope renders visible the prominence-lines

the prominences themselves.

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

CHAPTER IV.

STUDY OF THE SUN'S SURFACE.

Discovery of the spots

Narrative of Fabricius

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

143

145

Schwabe's discovery of the periodicity of spot-frequency

Associated period of magnetic disturbance

194

200

PAGE

Relative position of spots and faculæ

Views as to planetary action on solar surface

General results as to umbræ, penumbræ, and faculæ .

216

216

Formation, enlargement, and disappearance of spots

Whirling motion in some spots

Vast dimensions of Sun-spots

Rapid changes

Spectroscopic analysis of spots, &c.

Evidence given by the polariscope

Conclusion.

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) .

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

PAGE

290

291

Dr. Huggins succeeds in seeing the prominences themselves.
Observations by Lockyer on Huggins's plan

Respighi's daily views of the prominences and chromosphere

His account of the phenomena they present

The eclipse of August 1869

310

Professor Young photographs a prominence when the Sun is not

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

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 Lane's

General Myer's

a

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 .

Evidence as to meteoric systems .

As to cometic systems.

Leverrier's intra-Mercurial planets

Baxendell's intra-Mercurial zone or disc

Positive and negative evidence corroboratory

The radial beams considered

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

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

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

393

393

395

The enormous force-income' which may thus become available

405

The Meteoric theory and the theory of Helmholtz

Conclusion-reflections of Professor Tyndall

CHAPTER IX.

THE SUN AMONG HIS PEERS.

407

409

410

The Sun in the sidereal system

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

another in the Northern heavens.

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

Dissimilar helicoidal paths of the planets

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

Groups of companion suns

Conclusion

APPENDIX A.

APPROACHING TRANSITS OF VENUS AND THE BEST

MEANS FOR OBSERVING THEM.

Interest of the subject

Theory of transits

Transit of 1874 .

Places suitable for applying Delisle's methcd:

At ingress

At egress