ond. The law is, indeed, neither simple nor constant. Different
investigators have arrived at different formulae, which, being purely
empirical, vary their nature with the conditions of experiment. Probably
the best expedient for overcoming the difficulty is that devised by
Pickering, of simultaneously photographing a star and its secondary
image, reduced in brightness by a known amount.[1611] The results of its
use will be exhibited in a catalogue of 40,000 stars to the tenth
magnitude, one for each square degree of the heavens. A photographic
photometry of all the lucid stars, modelled on the visual photometry of
1884, is promised from the same copious source of novelties. The
magnitudes of the stars in the Draper Catalogue were determined, so to
speak, spectrographically. The quantity measured in all cases was the
intensity of the hydrogen line near G. By the employment of this
definite and uniform test, results were obtained, of special value
indeed, but in strong disaccord with those given by less exclusive
determinations.

Thought, meantime, cannot be held aloof from the great subject upon the
future illustration of which so much patient industry is being expended.
Nor are partial glimpses denied to us of relations fully discoverable,
perhaps, only through centuries of toil. Some important points in
cosmical economy have, indeed, become quite clear within the last fifty
years, and scarcely any longer admit of a difference of opinion. One of
these is that of the true status of nebulae.

This was virtually settled by Sir J. Herschel's description in 1847 of
the structure of the Magellanic clouds; but it was not until Whewell, in
1853, and Herbert Spencer, in 1858,[1612] enforced the conclusions
necessarily to be derived therefrom that the conception of the nebulae as
remote galaxies, which Lord Rosse's resolution of many into stellar
points had appeared to support, began to withdraw into the region of
discarded and half-forgotten speculations. In the Nubeculae, as Whewell
insisted,[1613] "there coexist, in a limited compass and in
indiscriminate position, stars, clusters of stars, nebulae, regular and
irregular, and nebulous streaks and patches. These, then, are different
kinds of things in themselves, not merely different to us. There are
such things as nebulae side by side with stars and with clusters of
stars. Nebulous matter resolvable occurs close to nebulous matter
irresolvable."

This argument from coexist