ens in a way that
had never been accomplished before.

The result of the combined labours of the two Herschels has placed
information of the nebulae at our disposal which is invaluable. Several
thousands of different nebulae are now known to us, and as the telescope
is improved and its powers increased, fresh nebulae are being added to
the number. Like stars, nebulae vary not only in size, but also in
colour, shape, and even in the materials of which they are composed.
They also vary in brightness, the light from some being much fainter
than the light from others.

It has been estimated by Huggins that the light received from a nebula
will not exceed the light of a sperm candle looked at from a distance of
a quarter of a mile. It is thought by some astronomers that the light
received from a nebula is indicative of the stage of development to
which it has arrived. Where the light is faint, the nebulae are in their
first stages of formation, and where it is brighter it is indicative of
a more advanced stage of development. Thus nebulae may consist of
nebulous matter in various stages of condensation, but they are not yet
in that condition which corresponds to the condition supposed to exist
in our sun.

Nearly all the nebulae lie outside the Milky Way, so that it would seem
as if in ages past all the nebulae that had ever existed in this starry
zone had passed out of their nebulous condition and been further
condensed into suns or stars, as they are called. Astronomical
observations teach us that there are very few nebulae indeed to be seen
in this starry highway, the part of the heavens which are richest in
them lying far beyond the confines of this zone. For many years certain
aggregations of luminous points in the heavens were supposed to be
nebulae, but by the aid of more powerful telescopes they have now been
resolved into clusters of stars. One of these clusters is the cluster in
Hercules, while another is the great nebula of Orion. In the case of the
former, situated in the constellation of Hercules, we find a great
number of very small points of light grouped together in a more or less
globular form. When looked at through a small telescope, this object
looks like a nebula, but looked at through Lord Rosse's, or some other
great telescope, it becomes at once resolved into an immense number of
separate points of light, each one representing a star, there being
between one and two thousand altogether in this cons