telescope. It tells whether any luminous body sends us its own, or
reflected light. Only one comet bright enough to be examined has
appeared since its perfection. This was Coggia's, and was found to
reflect solar from the tail, and to radiate its own light from the
nucleus.

Still another intricate instrument is in use, the thermograph, that
utilizes the heat rays from the sun, instead of the light. It takes
pictures by heat; in other words, it sees in the dark; brings invisible
things to the eye of man, and is used in astronomical and physical
researches wherein undulations and radiations are concerned. And now
comes the magnetometer, to measure the amount of magnetism that reaches
the earth from the sun. It points to zero when the magnetic forces of
the earth are in equilibrium, but let a magnetic storm occur anywhere
in the world and the pointer will move by invisible power. It detects a
close relation between the magnetism of the earth and sun. The needle is
deflected every time a solar disturbance takes place. At Kew, England,
an astronomer was viewing the sun with a telescope and observed a tongue
of flame dart across a spot whose diameter was thirty-three thousand
seven hundred miles. The magnetometer was violently agitated at once,
showing that whatever magnetism may be, its influence traversed the
distance of the sun with a velocity greater than that of light.

Not less remarkable is the new instrument, the thermal balance,
devised by Prof. S. P. Langley, Pittsburgh. It will measure the
one-fifty-thousandth part of a degree of heat, and consists of strips
of platinum one-thirty-second of an inch wide and one-fourth of an inch
long; and so thin that it requires fifty to equal the thickness of
tissue paper, placed in the circuit of electricity running to a
galvanometer. "When mounted in a reflected telescope it will record the