ness of the Parallactic Ellipse Illustrated--The
Case of 61 Cygni--Different Comparison Stars used--The Proper
Motion of the Star--Struve's Investigations--Can they be
Reconciled?--Researches at Dunsink--Conclusion obtained--Accuracy
which such Observations admit Examined--The Proper Motion of 61
Cygni--The Permanence of the Sidereal Heavens--The New Star in
Cygnus--Its History--No Appreciable Parallax--A Mighty Outburst of
Light--The Movement of the Solar System through Space--Herschel's
Discovery--Journey towards Lyra--Probabilities.

We have long known the dimensions of the solar system with more or less
accuracy. Our knowledge includes the distances of the planets and the
comets from the sun, as well as their movements. We have also
considerable knowledge of the diameters and the masses of many of the
different bodies which belong to the solar system. We have long known,
in fact, many details of the isolated group nestled together under the
protection of the sun. The problem for consideration in the present
chapter involves a still grander survey than is required for measures of
our solar system. We propose to carry the sounding-line across the vast
abyss which separates the group of bodies closely associated about our
sun from the other stars which are scattered through the realms of
space. For centuries the great problem of star distance has engaged the
attention of those who have studied the heavens. It would be impossible
to attempt here even an outline of the various researches which have
been made on the subject. In the limited survey which we can make, we
must glance first at the remarkable speculative efforts which have been
directed to the problem, and then we shall refer to those labours which
have introduced the problem into the region of accurate astronomy.

No attempt to solve the problem of the absolute distances of the stars
was successful until many years after Herschel's labours were closed.
Fresh generations of astronomers, armed with fresh appliances, have for
many years pursued the subject with unremitting diligence, but for a
long time the effort seemed hopeless. The distances of the stars were so
great that they could not be ascertained until the utmost refinements of
mechanical skill and the most elaborate methods of mathematical
calculation were brought to converge on the difficulty. At last it was
found that the problem was beginning to yield. A few st