ASTRONOMY. ri 
composed of substances incessantly darted out by the sun and falling back on 
him. (2) The coronal substance may be more or less supported in the solar 
heights by the effect of a calorific or electrical repulsion. (3) Finally, the corona 
may be due to clouds of meteors, aerolites circulating around the sun in his im- 
mediate vicinity. All these explanations are perhaps in part true.”’ 
In Proctor and Ranyard’s ‘‘Old and New Astronomy’’ we read as follows: 
‘‘But it is evident on the one hand that no simple theory can be advanced in 
explanation of the phenomena of solar appendages manifestly complex and 
varied; and on the other, that the details of coronal structure and of coronal 
phenomena present problems far too difficult to be as yet solvable.”’ 
Miss Clerke, in her ‘‘ History of Astronomy during the Nineteenth Century,’’ 
says: ‘‘The corona is properly described as a solar appendage, and may be con- 
jecturally defined as matter in a perpetual state of efflux from and influx to our 
great luminary, under the stress of electrical repulsion in one direction and of 
gravity in the other. Its constitution is of a composite character. It is partly 
made up of self-luminous gases, chiefly hydrogen, and the unknown substance 
giving the green ray, ‘1474,’ partly of white-hot, solid or liquid particles, shin- 
ing with continuous light, both reflected and original. The coronal materials 
must be of inconceivable tenuity, since comets cut their way through them with- 
out experiencing sensible retardation. Summing up what we have learned about 
the corona during some forty-five minutes of scrutiny in as many years, we may 
state, to begin with, that it is not a solar atmosphere. It does not gravitate 
upon the sun’s surface and share his rotation, as our air gravitates upon and 
shares the rotation of the earth; and this for the simple reason that there is no 
visible growth of pressure downward in its gaseous constituents; whereas, un- 
der the sole influence of the sun’s attractive power, their density should be mul- 
tiplied many million times in the descent through a mere fraction of their actual 
depth.”’ 
It is easily seen from the preceding extracts that the corona of the sun has 
been visible only on those rare occasions when solar eclipses are total; and the 
very short period of time during which a total eclipse lasts at any given point 
upon the earth’s surface renders any examination of the corona a very difficult 
operation. Since the introduction of the camera and the spectroscope as ad- 
juncts in all solar research, the amount of time and labor devoted to such work 
has been multiplied more than twofold. All the great observatories of the world 
are systematically engaged in trying to solve the mystery of the corona. Moun- 
tain peaks, clear skies and rare atmospheres have been sought for, and expensive 
trips to far-away lands have been undertaken, in order to determine once for all 
what this wonderful thing may be which persists in withholding from the in- 
quisitive eye its secrets and its nature. Men have gone half way round the globe 
to witness for one, two, or six or seven minutes at most, the most beautiful ob- 
ject visible in the solar system. The question naturally arises, Is it possible, or 
will it ever be possible, for the human eye, with or without any kind of instru- 
ment, and at any time, to look upon and examine at leisure such a glorious 
appendage as that of the sun’s corona? Will this nineteenth century, so full of 
splendid achievement in every field of scientific research, add to its other honors 
that of having made it possible, in the absence of a total eclipse, to see the 
corona? All efforts hitherto made have been without avail; have utterly failed. 
In 1866 Mr. Lockyer, and in 1868 Janssen, made it possible for one to see at 
- any time of day, when the sun is above the horizon and not obscured by clouds, 
the so-called ‘‘ protuberances”’ or ‘‘ prominences’’ that up to that time had been 
considered as mysterious as the corona is now. Miss Clerke says: ‘The eclipse 
