. In
future, therefore, we shall look upon those regions into which we
may now penetrate by means of such large telescopes, as a naturalist
regards a rich extent of ground or chain of mountains containing
strata variously inclined and directed, as well as consisting of
very different materials. The surface of a globe or map, therefore,
will but ill delineate the interior parts of the heavens."

HERSCHEL'S method of study was founded on a mode of observation which he
called _star-gauging_. It consisted in pointing a powerful telescope
toward various parts of the heavens, and ascertaining by actual count
how thick the stars were in each region. His twenty-foot reflector was
provided with such an eye-piece that, in looking into it, he saw a
portion of the heavens about 15' in diameter. A circle of this size on
the celestial sphere has about one quarter the apparent surface of the
sun, or of the full moon. On pointing the telescope in any direction, a
greater or less number of stars were visible. These were counted, and
the direction in which the telescope pointed was noted. Gauges of this
kind were made in all parts of the sky, and the results were tabulated
in the order of right ascension.

The following is an extract from the gauges, and gives the average
number of stars in each field at the points noted in right ascension and
north polar distance:

-----------------------------------------------------------------
| N. P. D. || | N. P. D.
R. A. |78 deg. to 80 deg. || R. A. |92 deg. to 94 deg.
| No. of Stars. || | No. of Stars.
------------|-------------------||-----------|-------------------
H. M. | || H. M. |
11 6 | 3.1 || 15 10 | 9.4
12 31 | 3.4 || 15 22 | 10.6
12 44 | 4.6 || 15 47 | 10.6
12 49 | 3.9 || 16 8 | 12.1
13 5 | 3.8 || 16 25 | 13.6
14 30 | 3.6 || 16 37 | 18.6
-----------------------------------------------------------------

In this small table, it is plain that a different law of clustering or
of distribution obtains in the two regions. Such differences are still
more marked, if we compare the extreme cases found by HERSCHEL, as
R. A. = 19h 41m, N. P. D. = 74 deg. 33', number of stars per