bridge, Massachusetts, and represents the less technical
subjects discussed in a series of lectures which I gave
in 1929 as Exchange Professor from Harvard University
to Carleton, Knox, and Pomona Colleges.

The rather extended emphasis on the work of some
of the pioneers will, it is hoped, introduce a human
touch to the romance of astronomical science, though
the treatment of the characters can hardly be con-
sidered biographical.

Acknowledgment is due to Mr. Josef Johnson for
reading the manuscript and proof, and to other col-
leagues for many helpful suggestions. To my wife,
Florence Brigham Stetson, I owe more than can here be
expressed, not only for attending to many details in-
cluding the preparation of the index, but for the in-
spiration and encouragement which has made the
writing a pleasure.

For permission to quote from Alfred Noyes' Watchers
of the Sky ( 1922). I am indebted to the F. A. Stokes
Company, Publishers, New York.

HARLAN TRUE STETSON.

PERKINS OBSERVATORY,
DELAWARE, OHIO.
October, 1930.

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