612 The Philippine Journal of Science 1920 
Columns 8 and 9 give data about the contact of 1, lower, and 
2, upper limb with the horizon; 1, indicates a suspicion that the 
instant recorded was actually a little tardy; a, perfect contact 
without blurring; b, less perfect but quite definite. 
In the column “Remarks,” “Colton phenomena,” refers to those 
peculiar deformations of the sun’s limb and face which were 
first accurately recorded by A. L. Colton, whose sunset photo- 
graphs made in 1893 still adorn the corridors on Mount Hamilton. 
These deformations are always present as little ripples on the 
edge, and may be exaggerated into steps, or notches, or incised 
gashes, or projecting horns, or the disk may even be split or 
doubled. They are frequently notable at sea level; at Mount 
Mirador they are sometimes quite wonderful. They deserve 
photographic record and careful study, as they afford an optical 
analysis of the atmosphere from sea level to a great height. 
In the course of these observations I have distinguished two 
types of marine sunset, A and B. 
Type A occurs always when mirage is perceptible, and some- 
times when it is not, and its observed duration was very nearly 
equal to the computed, and more nearly as practice and experi- 
ence gave skill in observation; the agreement is best in those 
cases where an unshaded telescope and a stopwatch were used, 
as in Nos. 39 to 41. As the descending sun, vertically com- 
pressed by astronomical refraction, approaches the sea horizon, 
a protuberance of more or less flatness grows out below, and 
almost simultaneously a line of light appears in the sea 
horizon, which lengthens horizontally and thickens upward till 
the protuberance and the line join; the moment of this junction 
I have called lower contact, 1. For about half the duration of 
sunset the sun presents the appearance of an inverted fish globe, 
whose mouth rapidly widens to the sun’s diameter; from then 
on the vanishing disk looks like an ellipse much flattened below, 
and vanishes aS a small elliptical spot, at upper contact, 2. 
This spot does not sink below the horizon; it “goes out.” 
Type B never occurs simultaneously with a perceptible mirage, 
and its observed duration was always greater than the computed, 
by even as much as 20 or 25 seconds. The descending sun flattens 
below as it approaches the horizon, which is not always easy to 
see under it, being comparatively dark. The corners of the disk 
as it passes below the horizon are rounded, instead of projecting 
2 Colton, A. L., Sunsets at Mt. Hamilton—some curious effects of refrac- 
tion, Contributions from the Lick Observatory, No. 5 (1895). 
