an organ of sense is placed in the resisting object, it will judge the
direction of the waves or the direction of the object producing them by
a line at right angles with the wave front. Now suppose a body is placed
between the body producing the waves and the sensitive organ. The waves
must go around this body and will produce an eddy behind it, so that the
wave front will have a different direction, and the organ of sense will
conceive the origin of the waves to lie in a direction different from
that before the body was interposed. Now consider the waves to be waves
of light, and their origin the sun. The organ of sense is the retina of
the eye. The moon is the opaque body interposed in the course of the
waves, and they, being bent, make the impression on the eye that the
light comes from beyond the edge of the sun. The moon covers the sun
during the eclipse and a little more, so that it can move for about five
minutes and still cover the sun entirely. This movement is very slight,
and if the corona consists of light from a solar atmosphere, it should
not change at all during this movement of the moon. But if diffraction
is the cause of the light, then the slightest change in the relative
positions of the sun and the moon should change the configuration of the
corona, i.e., the corona should not remain exactly the same during
a total eclipse. The character of the light as shown by a spectrum
analysis should change.

To determine this point Dr. Hastings invented the following instrument:
Two lozenge-shaped prisms of glass were fastened in the form of a letter
V, and so arranged that all the light falling within the aperture of
the V was lost, and that falling on the ends of the glass prisms was
transmitted by a series of reflections to the apex of the V, where the
prisms touched; here was placed a refracting prism, so that the light
could be analyzed. This instrument was attached to the eye piece of the
telescope, and the image of the eclipse reduced to such a size that the