telescope, micrometer, heliostat, and spectroscope came desire for more
complex instruments, resulting in the invention of the photoheliograph,
invoking the aid of photography to make permanent the results of these
exciting researches. This mechanism consists of an excessively sensitive
plate, adjusted in the solar focus of the telespectroscope. In front
of the plate in the camera is a screen attached to a spring, and held
closed by a cord. The eye is applied to the spectroscopic end of the
complex arrangement to watch the development of solar hurricanes.

Finally an appalling outburst occurs; the flames leap higher and higher,
torn into a thousand shreds, presenting a scene that language is
powerless to describe. When the display is at the height of its
magnificence, the astronomer cuts the cord; the slide makes an exposure
of one-three thousandth part of a second, and an accurate photograph
is taken. The storm all in rapid motion is petrified on the plate;
everything is distinct, all the surging billows of fire, boilings, and
turbulence are rendered motionless with the velocity of lightning.

At Meudon, in France, M. Janssen takes these instantaneous photographs
of the sun, thirty inches in diameter, and afterward enlarges them to
ten feet; showing scenes of fiery desolation that appalls the human
imagination. (See address of Vice President Langley, A. A. A. S.,
Proceedings Saratoga Meeting, p. 56.) This huge photograph can be viewed
in detail with a small telescope and micrometer, and the crests of solar
waves measured. Many of these billows of fire are in dimensions
every way equal in size to the State of Illinois. Binary stars are
photographed so that in time to come they can be retaken, when if they
have moved, the precise amount can be measured.

Another instrument is the telepolariscope, to be attached to a