TOTAL SOLAE ECLIPSE OF JULY 18, 1860. 
373 
mere inspection, of the genera] distribution in heliocentric latitude of these appendages. 
Plate XVI. was obtained by etching a positive copy of No. 22 photograph, and 
Plate XVII. by etching one of No. 28 photograph. These photographs were obtained 
with the same setting of the copjdng-camera as the sun-picture, the original of Plate XV. 
They show the contour’s of the sun and moon, and furnish a means for comparing the 
concave outline of the luminous prominences with the profile of the moon which was 
in juxtaposition with it. 
Reserving, for the present, an account of the measurements actually made on the 
engraved-glass originals of Plates XIII., XIV., and XV., I will proceed to describe a new 
measuring-instrument, and the measurements made by its means, not only of the totality- 
pictures, but also of the original negatives of the sun taken before and after the eclipse, 
as well as of the different phases of the eclipse. These consist of the direct measure- 
ment of the sun’s radius, the du’ect measurement of the moon’s radius (where possible), 
the measurement of the chord joining the cusps, the measurement of the distance 
between the chord and the peripheries of the sun and the moorr, and also the distances 
of these peripheries, the determinatioir of the angles of position of the cusps, and their 
angular openings, and, lastly, the positiorr-arrgles of the lumirrous prominences. The 
heights of the prominences could not be determined by means of the micrometer, in 
consequence of an inadvertence on the part of the makers, who by mistake made it 
somewhat too small; here, however, the engraved-glass originals of Plates XIII., XIV., 
and XV. supply the numbers with sufficient accuracy, so that this oversight is of iro 
practical moment. 
Figures I and 2 represent the micrometer in two different positions. 
Fig. 1. 
3 E 
MDCCCLXII 
