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22 PHILOSOPHICAL SOCIETY OF WASHINGTON. 
the plate-holder, the operator moved the exposing slide, and the 
time of exposure was recorded on the chronograph. 
For observing contacts I used an eye piece, magnifying 216 diam- 
eters, attached to a Herschel solar prism, and a sliding shade-glass 
with a density varying uniformly from end to end. The time of 
my signals was taken by assistant astronomer Lieut. J. A. Norris, 
U.S. N., from a chronometer; while, with an observing key, I also 
made a record on the chronograph as a check. 
About 40 seconds before the computed time of first contact a 
narrow stratus cloud passed on to the southeastern edge of the sun 
and shut out all the light. The cloud remained about 3 minutes, 
and when it passed off, the notch in the sun’s limb was plainly 
marked. Two photographs were taken to test the apparatus and 
the plates, and then the time before second contact was devoted to 
an examination of the limbs of Venus and the sun. Both were 
perfectly steady. In observations of the sun for the last twenty 
years I never saw it better. At about 13 minutes after first contact 
the outline of the entire disk of Venus could be seen, and seemed 
perfectly circular. About 2 minutes later a faint, thin rim of 
yellowish light appeared around the limb yet outside the sun. This 
rim was at first broadest near the sun’s limb, but soon the width of 
the light became uniform throughout. The light was wholly ex- 
terior to the limb of Venus; that is, the black limb of Venus on 
the sun and the dark limb outside formed a perfectly circular disk, 
with the rim of light or halo, outside the portion off the sun. As 
the time of second contact approached, Lieutenant Norris again 
took up his station at the chronometer. As the limbs neared geo- 
metrical contact, the cusps of sunlight began to close around Venus 
more rapidly; and the perfect definition of the limbs and the steady, 
deliberate, but uniformly increasing motion of the cusps, convinced 
me instantly that the phenomena attending the contact would be 
far more simple than I had ever imagined. I had only to look 
steadily to see the cusps steadily but rapidly extend themselves into 
the thinnest visible thread of light around the following limb of 
Venus and remain there without a tremor or pulsatiom At the 
moment the cusps joined I gave the signal and also made the 
record on the chronograph. Still keeping my eye at the telescope, 
I saw nothing to note save the gradually increasing line of light 
between the limbs of the two bodies. The disk of Venus on the 
sun was black. 
