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THE HISTORY AND WORK OF
HARVARD OBSERVATORY
1839 to 1927
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HARVARD OBSERVATORY MONOGRAPHS
No. 4
The History and Work
of Harvard Observatory
1839 to 1927
An Outline of the Origin, Development, and
Researches of the Astronomical Observatory
of Harvard College together with Brief Biog-
raphies of Its Leading Members
BY
SOLON I. BAILEY
Published for the Observatory
by the
McGRAW-HILL BOOK COMPANY, INC.
NEW YORK AND LONDON
1931
COPYRIGHT, 1931,
BY HARVARD OBSERVATORY
PRINTED IN THE UNITED STATES OF AMERICA.
All rights reserved. This bookj or
parts thereof, may not be reproduced
in any form without permission of
the publishers.
THE MAPLE PRESS COMPANY, YORK, PA.
PREFACE
THIS book has been prepared at the suggestion of Dr. Harlow
Shapley, Director of the Harvard College Observatory. Indeed,
a similar request had been made several years earlier by Profes-
sor E. C. Pickering, the preceding director. The author has
been associated with the Observatory since 1887 an d during
this time has had favorable opportunities to become familiar
with its varied activities. From the limitations imposed by the
size of the volume, little more than an outline of the subjects
presented has been possible. In Section II a discussion is given
of only the more important researches undertaken by the
members of the Observatory. An account of many investigations
of which no explicit mention is made in this book may be
found by reference to the publications enumerated in Chapter
VI.
The author acknowledges the assistance which has been
generously given him by other members of the Observatory
Staff, by Professors Edward S. King and Willard P. Gerrish,
Dr. Willard J. Fisher, Mr. Leon Campbell, Dr. Annie J. Cannon,
Mrs. Doris M. Wills, Miss Constance D. Boyd, and especially
Dr. Cecilia H. Payne and Dr. Harlow Shapley.
S. I. B.
CAMBRIDGE, MASS.,
April, 1931.
CONTENTS
PAGE
PREFACE vii
PART I
HISTORICAL OUTLINE
CHAPTER
I. THE ANCESTRY OF THE HARVARD OBSERVATORY 3
Foundation of Harvard College 4
Early Astronomy in Massachusetts 5
The Venus Expedition of 1761 6
Career of John Winthrop 7
Foundation of the American Academy 8
The Harvard Eclipse Expedition of 1780 ... 8
Bowditch and Sumner 10
The Harvard Observatory First Planned n
Foundation of the Harvard Observatory 14
II. THE OBSERVATORY AT THE DANA HOUSE . . . . ... 17
The Early Astronomical Equipment . ... 17
The Naming of the Observatory. . 19
Standing of the Observatory in the University . 20
The Observatory and the Public 21
III. GROWTH OF THE PRESENT OBSERVATORY . . 23
Endowment of the New Observatory 23
The Observatory Transferred to the Present Site 25
Installation of the 1 5-inch Refractor 26
Additions to the Equipment ... . . ... 27
The Phillips Bequest . 30
The Cambridge Astronomical Society 31
The First Directors; William and George Bond . . . . 32
Appointment of Joseph Winlock . -33
Development of the Observatory under Pickering 35
Shapley Chosen Director 37
IV. INSTRUMENTAL EQUIPMENT 38
The Chronograph 38
The is-inch Visual Refractor 39
Transit Instruments 41
The Photographic Doublets 42
The Draper and Boyden Refractors 44
The Polar Equatorial 45
ix
X CONTENTS
CHAPTER PAGE
The Meridian Photometers 46
The 6o-inch Reflector . 47
Miscellaneous Instruments 48
V. EXPEDITIONS AND FOREIGN STATIONS 50
Total Eclipse of the Sun, 1851 50
Annular Eclipse of the Sun, 1854 . . 51
Determinations of Longitude, 1855 . 51
Total Eclipse of the Sun, 1869 ... ... 51
Total Eclipse of the Sun, 1870 . ... -52
Total Eclipse of the Sun, 1886 . . 54
Total Eclipse of the Sun, 1887 . 54
The Boy den Expeditions, 1887 to 1888. 55
Total Eclipse of the Sun, 1889 .... 56
The Mount Wilson Station, 1889 to 1890. 56
First Peruvian Expedition, 1889. . 58
Second Peruvian Expedition, 1891; the Arequipa blalion. . . 60
Minor Peruvian Expeditions 61
First Jamaican Expedition, 1899. . . -63
Total Eclipse of the Sun, 1900 . . ... 63
Second Jamaican Expedition, 1900 to 1901 . . . 63
First South African Expedition, 1908 to 1909 . . -64
The Station at Mandeville, Jamaica, 1912 . . .66
Chuquicamata and San Jos6 Stations, 1923 to 1920 . . 66
Total Eclipse of the Sun, 1925 67
The New Southern Station at luazclspoort, near iJloemfontein,
1927 68
VI. PUBLICATION OF SCIENTIFIC REbULis 70
The Harvard Annals 70
The Harvard Circulars. 71
The Harvard Bulletins. 72
Harvard Announcement Cards 73
Harvard Reprints 73
The Annual Reports .... . . 74
Harvard Monographs 74
Miscellaneous 75
PART II
THE SCIENTIFIC PROBLEMS
VII. THE SOLAR SYSTEM 79
The Brightness of the Sun 79
The Solar Spectrum 81
The Moon's Brightness. . . . 81
The Surface of the Moon 82
Lunar Eclipses 84
Determination of the Moon's Position 85
CONTENTS xi
CHAPTER PAGE
The Planets and Their Satellites 86
Eclipses of Jupiter's Satellites 88
Planetary Observations by W. H. Pickering 89
The Ninth Satellite of Saturn 90
The Surface of Mars. 90
The Transneptunian Planet 91
The Asteroids 92
Variability of Eros. ... 93
Discovery and Observation ot Comets 94
VIII. TERRESTRIAL PROBLEMS 96
The Study of Meteor 96
Meteorology 100
Terrestrial Magnetism 102
Geodesy 104
IX. ASTRONOMY OF POSITION ir8
The Bond Zones 108
Transit Observations no
Micrometric Measures no
Meridian Circle no
The Almucantar 113
X. ASTRONOMICAL PHOTOGRAPHY 115
Beginnings of Astronomical Photography 115
Progress of Stellar Photography 116
Henry Draper and the Beginnings of Stellar Spectroscopy . . .118
Astronomical Photography under Pickering 119
Construction and Guiding of Astronomical Cameras 120
The Photographic Image 121
XI. STELLAR PHOTOMETRY, VISUAL AND PHOTOGRAPHIC. . ... 123
The Beginnings of Photometry ... . 123
Peirce's Early Photometric Experiments 124
The Polarizing Photometer and the 1 5-inch Telescope . . . . 125
The Harvard Photometry and its Extensions 127
Photographic Photometry 135
King's " Absolute" Measures of Photographic Magnitude . . . 137
The North Polar Sequence 139
The Standard Regions 141
Standards of Magnitude for the Astrographic Catalogue . . . 142
Kapteyn's Plan of Selected Areas 143
Photovisual Photometry 144
Miscellaneous Results 146
XII. SPECTROSCOPY. ... 148
Visual Spectroscopy . 148
Early Photography of Spectra 149
The First Draper Catalogue 150
xii CONTENTS
CHAPTER PACK
Miss Maury's Pioneer Analyses of Spectra 152
Miss Cannon and the Draper Classification 154
The Henry Draper Catalogue 156
The Henry Draper Extension 158
Discussions of the Henry Draper Catalogue. . . ... 159
Miscellaneous Problems .164
The Spectroscopy of Novae . . . 165
Double Star Spectroscopy . . . . . 166
Spectroscopic Parallaxes . . . .167
Development of Spectrophotometry . . 168
XIII. VARIABLE STARS AND NOVAE. . . . . . 170
Classification of Variable Stars ... . . . 170
Amateur Observations of Variables . .171
The Harvard Catalogues of Variable Stars 172
The Naming of Variable Stars 172
Visual Photometry of Variable Stars 174
Standard Magnitudes for Published Observations 175
Visual Observations at Harvard 176
Photographic Methods for Variable Stars 179
Variable Stars in Globular Clusters 181
The Magellanic Clouds 184
The Period-Luminosity Curve 185
The Novae 185
The Amateur's Contribution; the A. A. V.S.O 189
XIV. CLUSTERS AND NEBULAE. 192
Stellar Clusters 192
Investigations of Nebulae 194
XV. STRUCTURE AND DIMENSIONS OF STELLAR SYSTEMS . . . 198
Peirce's Survey of the Galactic System 198
Pickering's Studies of the Milky Way . . . . 199
Miscellaneous Investigations of the Milky Way 200
Shapley's Measurement of the Galaxy 201
Details of the Solar Neighborhood 206
The Magellanic Clouds 206
Extra-galactic Systems 211
PART III
BIOGRAPHICAL SKETCHES
XVI. THE BONDS 217
William Cranch Bond 217
George Phillips Bond 226
XVII. WlNLOCK AND PICKERING 237
Joseph Winlock 237
Edward Charles Pickering 243
CONTENTS xiii
CHAPTER PAGE
XVIII. LEADING MEMBERS OF THE OBSERVATORY STAFF 253
Charles Wesley Tuttle 253
fitienne Leopold Trouvelot 254
Asaph Hall 254
William Augustus Rogers. .. 255
Samuel Pierpont Langley 256
Truman Henry Safford. . 257
Arthur Searle 258
George Mary Searle . . . ... 259
Charles Sanders Peirce 260
Oliver Clinton Wendell. . . . . . 261
John Rayner Edmands. . 261
Winslow Upton . . . 262
Williamina Paton Fleming . . 263
Henrietta Swan Leavitt . . . . . . . 264
XIX. RESEARCH ASSOCIATES OF THE OBSERVATORY . ... . . 266
Sydney Coolidge . 266
Seth Carlo Chandler 266
Abbott Lawrence Rotch . . .... 268
Joel Hastings Metcalf 268
Henry Gannett 270
Nathaniel S. Shaler 270
Henry M. Parkhurst. . . 270
Dana P. Bartlett .... 270
Harry E. Clifford 270
George E. Hale . 271
Robert DeCourcy Ward 271
George K. Burgess ... 271
Frederick W. Grover ... 271
Ralph A. Sampson ... 271
Clarence A. Chant 271
Herbert C. Wilson 271
Jacobus C. Kapteyn ... 271
Ejnar Hertzsprung 272
XX. LIST OF OBSERVATORY STAFF MEMBERS 273
XXL BENEFACTORS OF THE OBSERVATORY 277
Past and Present Benefactors 277
Edward Bromfield Phillips 279
Robert Treat Paine 280
Uriah Atherton Boyden 281
Miss Catherine Wolfe Bruce 282
Anna Palmer Draper (Mrs. Henry Draper) 283
Charles Robert Cross 283
NAME INDEX 285
SUBJECT INDEX 293
PART I
HISTORICAL OUTLINE
THE HISTORY AND WORK
OF THE
HARVARD OBSERVATORY
CHAPTER I
THE ANCESTRY OF THE HARVARD OBSERVATORY
THE Harvard Observatory was established by an official
act of the Corporation of Harvard University in October, 1839.
The first director (who possessed the title of Astronomical
Observer) was appointed at that time and observations were
begun at the end of that year. A number of other astronomical
observatories were founded in the United States in the first
half of the nineteenth century as a result of the general quicken-
ing of scientific interest; but the beginnings of that interest
appeared much earlier, and were intimately connected with
Massachusetts and with Harvard University.
In spite of the difficulty of direct communication with
European centers of thought, an interest in astronomical
science and discovery was by no means lacking in the Massa-
chusetts Bay Colony during the first century after its settle-
ment. European astronomy was still in its childhood; the
Paris Observatory was not founded until 1667, and the Green-
wich Observatory, not until 1675. Galileo died in 1642, the
year of Newton's birth, and six years after Harvard College
was founded. Newton's discoveries, though announced during
the last half of the seventeenth century, were not generally
familiar to the scientific world until the beginning of the
eighteenth. The Royal Astronomical Society was not founded
until 1820.
3
4 THE ANCESTRY OF THE HARVARD OBSERVATORY
Foundation of Harvard College. The Massachusetts
Bay Colony was founded about 1630. It is remarkable that
within its first decade, in 1636, this pioneer colony, by a vote
of its elected representatives, established a college for the educa-
tion of its youth. The college thus founded as a public charge
was early called Harvard College, after John Harvard, its
first private benefactor. It was intended especially to teach
and to perpetuate the religious doctrines of the early settlers.
A liberal spirit, nevertheless, breathed through the official
act.
After God had carried us safe to New England, and we had builded
our houses, provided necessaries for our liveli-hood, rear'd convenient
places for God's worship, and settled the Civill Government, one of the
next things we longed for, and looked after was to advance learning, and
perpetuate it to Posterity: dreading to leave an illiterate Ministry to the
Churches, when our present Ministers shall lie in the Dust.
The name of the town in which the college was placed was
changed from Newtown to Cambridge in 1638. Instruction
was begun in the same year, the first building having been
erected in 1637. For a long time the faculty of the College
consisted of a president and two or three tutors; yet even
in those early days astronomy was held in considerable esteem.
In 1642, the year of the first Commencement ceremonies,
according to "The Laws, Liberties and Orders of Harvard
College," it was declared that:
10. Every Scholar that giveth up in writing a synopsis or summary of
Logic, Natural and Moral Philosophy, Arithmetic, Geometry, and
Astronomy, and is ready to defend his theses or positions, withal skilled
in the originals as aforesaid, and still continues honest and studious, at
any public act after trial, he shall be capable of the second degree, of
Master of Arts. 1
Astronomy was not required for the lower degree of bachelor.
During the first century after its foundation, the struggle
and poverty of a pioneer community had their inevitable effects
on the life of the College, which was dependent, in large part,
1 Josiah Quincy, History of Harvard University, x, 517, 1840.
EARLY ASTRONOMY IN MASSACHUSETTS 5
on special state grants for its equipment and maintenance.
In addition to these difficulties there was almost continuous
dissension between the deep but narrow and dominating reli-
gious spirit of the times, and the more liberal element which
was never lacking. As President Quincy says: "Of all per-
secutors, politicians whose power depends upon a display of
religious zeal, are naturally the most bitter." 2
Early Astronomy in Massachusetts. Such an atmos-
phere was evidently none too favorable for the pursuit of
astronomical science. Something was nevertheless attempted,
and real contributions to science were made by such men as
Thomas Brattle. Born in 1657, he was graduated from Harvard
College in 1676, and was Treasurer of the College for 20 years.
He was distinguished among his contemporaries for his scientific
attainments:
Bailey in his supplement to the account of Flamsteed, states, that
"Mr. Thomas Brattle, of Boston in New England, is the anonymous
person alluded to by Newton, in his Principia, as having made such good
observations on the comet of i68o." 3 * 4
Mr. Brattle also observed the solar eclipse of June, 1694,
and the lunar eclipses of February, 1700, and December,
I7O3. 5 Among the transactions of the Royal Society of London
is a communication entitled "Observatio Eclipsis Lunaris
peracta Bostonii Novanglorum, die quinto Aprilis, Vespere,
A. D. 1707, a Tho. Brattle." 6 William Brattle, son of Thomas
Brattle, was a Fellow of the Royal Society of London, and, like
his father, a man of scientific tastes.
Although astronomy appears to have been taught since the
beginning of instruction at Harvard College, a professorship
of mathematics and natural philosophy was first established
*Ibid., p. 335.
8 Ibid., p. 412. By " Bailey," Francis Baily is meant.
4 Newton, Philosophiae Naturalis Principia Mathematica (Geneva Edition),
3 633, 634, 635, 638, 1742.
6 Phil. Trans. Roy. Soc. (abridged), 5, 148, 1704.
5379, 1707.
6 THE ANCESTRY OF THE HARVARD OBSERVATORY
there in 1727, through the generosity of Mr. Thomas Hollis.
The first appointment to this professorship seems to have been
an unfortunate one, but in 1738 John Winthrop, friend of
Benjamin Franklin, able scientist, and lover of astronomy,
was chosen for the position. Two years later he communicated
to the Royal Society of London a paper entitled " Observations
of the Transit of Mercury over the Sun." 7 These observations
were published in the Transactions 8 and were favorably noticed
in the Memoirs of the Royal Academy of Arts and Sciences at
Paris.
The Venus Expedition of 1761. Observations of the tran-
sit of Venus in 1761 were desired, and
Professor Winthrop was inspired with an intense desire to assist in
accomplishing this important object; and, as the transit was not visible
in the latitude of New England, he determined, if possible, to observe it
from Newfoundland. He therefore addressed a memorial to Governor
Bernard, who, entering cordially into his views, by a special message on
the subject, obtained from the Massachusetts Legislature leave to place
the Province sloop at his service for this purpose. 9
The plan was carried out successfully. Professor Winthrop,
with such apparatus suitable to his purpose as was in the
possession of the College, went to Newfoundland and observed
the transit on June 6, 1761. The expedition is worthy of
special attention, since it shows that astronomical interest was
strong in Massachusetts even at this early date.
The transit of 1769 was also observed by Winthrop, who was
doubtless placed at some disadvantage by the disastrous fire
of 1 764, referred to on page 7. This transit was visible, however,
over the eastern United States and was well observed in
Pennsylvania by Rittenhouse and others. Although Kitten-
house lacked the early educational and social advantages of
Winthrop, his native genius and his modesty brought him a
wide reputation, and the friendship of Washington, Franklin,
7 Josiah Quincy, op. cit., 2, 25.
8 Phil. Trans. Roy. Soc. (abridged), 8, 713, 1743.
9 Josiah Quincy, op. cit., 2, 22.
CAREER OF JOHN WINTHROP 7
and other eminent men of the day. He was eighteen years
younger than Winthrop. Although both astronomers were
members of the American Philosophical Society of Philadelphia,
they appear to have been but slightly acquainted, and little
correspondence passed between them.
Career of John Winthrop. Winthrop has been called the
first American astronomer. Belonging to one of the oldest and
most prominent families in New England, he enjoyed the best
social and educational advantages that Massachusetts could
offer. The duties of his professorship occupied the greater
part of his time, but he took part in many scientific investiga-
tions in mathematics, meteorology, and geodesy, as well as in
astronomy. He made no great discoveries but he gained a
wide reputation both in this country and abroad. He was
elected a Fellow of the Royal Society in 1765, and member of
the American Philosophical Society in 1768. He received
the degree of LL.D. from Edinburgh in 1771, and from Harvard
in 1773, the first time that degree had been awarded at Harvard
University. Winthrop died in 1779 at the age of sixty-five
years.
Under Winthrop's guidance, scientific observation and the
teaching of astronomy at Harvard attained real importance.
Both, however, were seriously retarded by the disastrous fire
that consumed Harvard Hall and all the instruments it con-
tained on the night of January 24, 1764.
For Astronomy, we had before been supplied with telescopes of different
lengths; one of 24 feet; and a brass quadrant of 2 feet radius, carrying a
telescope of a greater length, which formerly belonged to the celebrated
Dr. Halley. We had also the most useful instruments for dialling; and,
for surveying, a brass semi-circle with plain sights and magnetic needle.
Also, a curious Telescope, with a complete apparatus for taking differences
of level . . . [list of several donors] . . . From these gentlemen we
received fine reflecting telescopes of different magnifying powers, and
adapted to different observations; Microscopes of the several sorts now
in use; Hadley's quadrant, fitted in a new manner; a nice variation com-
pass, and dipping needle; with instruments for the several magnetical
8 THE ANCESTRY OF THE HARVARD OBSERVATORY
and electrical experiments, all new and of excellent workmanship. All
destroyed/ 10
Foundation of The American Academy. The American
Academy of Arts and Sciences was founded in 1780, while
the American Revolution was in progress. In 1785, the first
volume of the Memoirs was published. On page viii of the
Preface the editor states that:
The Astronomical and mathematical papers in the volume will, per-
haps, be the least entertaining of any in the collection, and will have the
smallest number of readers. However, they are useful in such a work.
Few, if any of them, contain deep speculations and abstruse researches
and calculations; but they are chiefly of the practical kind . . . These,
and all other mathematical pieces will be gratefully received, and due
attention paid to them by this body.
The volume contains 14 astronomical papers, which deal with
the determination of the difference in longitude between
Harvard Hall and Greenwich, the latitude of Cambridge,
the transit of Mercury in 1782, the solar eclipse of 1780, and
various other subjects. For many years astronomy had
evidently received much attention in Boston and the vicinity,
and especially at Harvard College. Of special significance
is the paper by Reverend Joseph Willard, President of Harvard
University, entitled "A Memoir Containing Observations
of a Solar Eclipse, October 27, 1780, made at Beverly; also,
of a Lunar Eclipse, March 29, 1782, of a Solar Eclipse, April 12,
and of the Transit of Mercury over the Sun's Disc, Novem-
ber 12, the same year, made at the President's House in
Cambridge." 11
The Harvard Eclipse Expedition of 1780. In May, 1780,
Reverend Samuel Williams was installed Hollis Professor of
Mathematics and Natural Philosophy. A paper by him
appears in the first volume of the Memoirs, giving an account
of his various astronomical observations made from 1761 to
1784. The paper includes a description of the solar eclipse of
10 Ibid., p. 483.
11 Mem. Amer. Acad., x, 129, 1785
PLATE I.- JOHN WINTHROP. (From a painting by Copley in the Faculty Room,
University Hall, Harvard University.)
(Facing page 8)
PLAIK II. THE IS-INCH REFRACTOR.
THE HARVARD ECLIPSE EXPEDITION OF 1780 9
1780, already mentioned, as observed by him at Penobscot
Bay in the present State of Maine, then a part of Massachusetts.
The Colonies were at this time at war with Great Britain, but,
for the second time in the history of Massachusetts a public
subsidy of the eclipse expedition bore witness to the value
that was placed upon astronomical observation. In regard
to this expedition Professor Williams states:
A favorable opportunity for viewing one of these eclipses occurring on
October 27, 1780, the American Academy of Arts and Sciences, and the
University at Cambridge, were desirous to have it properly observed in
the eastern part of the State, where, by calculation, it was expected it
would be total. With this view they solicited the Government of the Com-
monwealth, that a vessel might be prepared to convey proper observers
to Penobscot-Bay; and that application might be made to the officer
who commanded the British garrison there, for leave to take a situation
convenient for the purpose. Though involved in all the calamities and
distresses of a severe war, the Government discovered all the attention
and readiness to promote the cause of science, which could have been
expected in the most peaceable and prosperous times; and passed a
resolve, directing the Board of War to fit out the Lincoln Galley to convey
me to Penobscot, or any other part at the eastward, with such assistants
as I should judge necessary. 12
There was evidently much enthusiasm for the expedition,
and volunteers were numerous. Professor Williams selected
as his assistants Professor Sewall, Mr. Winthrop (librarian),
Mr. Vernon (a graduate), and Messrs. Atkinson, Davis, Hall,
Dawson, Rensselaer, and King, students in the College.
Although the British officer in command at Penobscot
Bay permitted the expedition to land, he imposed time limits
which were so brief as to afford small opportunity for preparing
the camp or for determining its position. The position of
the site was incorrectly given on the maps of the time, so that
an error of half a degree was made in its selection, and the
eclipse therefore appeared not quite total. Professor Williams
deserves no discredit for the error, and he seems to have made
the best of very difficult circumstances.
12 Ibid., p. 86.
10 THE ANCESTRY OF THE HARVARD OBSERVATORY
Bowditch and Sumner. The active and widely extended
interest in astronomical problems, long present in Massa-
chusetts, bore witness to the enduring influence of the large
element of University graduates among the early colonists.
An immense impetus to the scientific development of the colony
was also given by a few men of genius. Benjamin Franklin
and Benjamin Thompson (Count Rumford) were born in
Massachusetts and passed their earliest years here, and their
influence cannot have failed to foster a broader scientific outlook.
Among those in Massachusetts whose influence was greatest
in the development of mathematics and astronomy, and in the
establishment of the Harvard Observatory, was Nathaniel
Bowditch (1773 to 1838). He was born in humble circum-
stances, of New England stock, had few educational advantages
in youth, and was almost entirely self-taught. While young
he made five sea voyages, during which he devoted every spare
moment to study. His enthusiasm was contagious on one
ship every sailor, and even the cook, learned the art of naviga-
tion and could determine the position of the vessel with sufficient
precision.
Bowditch was the author of many astronomical papers, in
addition to his famous "New American Practical Navigator,"
and his translation of the "Mecanique Celeste" of Laplace.
Of this translation Legendre wrote, in 1832: "Your work is
not merely a translation with a commentary; I regard it as a
new edition, augmented and improved, and such as might
have come from the hand of the author himself."
Bowditch gained an international reputation in astronomy
and was deeply interested in the development of the science,
especially at Harvard. He was offered the position of Hollis
Professor of Mathematics and Natural Philosophy in 1806;
he also received flattering offers from different parts of the
country, all of which he declined. Harvard University con-
ferred on him the degree of LL.D. in 1816.
Another name prominent in the history of navigation
is that of Captain Thomas H. Sumner, an American shipmaster.
THE HARVARD OBSERVATORY FIRST PLANNED II
In 1843, Sumner published at Boston "A New and Accurate
Method of Finding a Ship's Position at Sea." The discovery
of this method proved to be of incalculable value to navigation.
Its essential feature consisted in the proof that a single observa-
tion of the sun's altitude determines the ship's position as
somewhere on a line the " Sumner line" whose direction
is readily determined. (This line is really a part of the so-called
" circle of position," but for convenience may be regarded as a
straight line at any point.) In America, Sumner's method
received the unqualified approval of Benjamin Peirce, and in
Europe, that of Lord Kelvin and others. A similar method
had already been tried, it is claimed, by officers of the British
Navy, but even if the claim is justified, the method remained
of little use until it had been simplified and made practical
by Sumner. The details of this method were later considerably
modified.
The Harvard Observatory First Planned. John Quincy
Adams, sixth President of the United States, was highly
influential in bringing about the establishment of the Harvard
Observatory. He also aided greatly in the development of
astronomy elsewhere, especially in forwarding the foundation
of the National Observatory at Washington, and in the dedica-
tion of the Cincinnati Observatory founded by General O.
M. Mitchel and built by the citizens of that city. To Josiah
Quincy, President of the University from 1829 to 1845, should
be given equal honor, as will be seen in subsequent pages.
The remarkable interest in astronomy, so well indicated
by the establishment of many observatories in America in
the first half of the nineteenth century, was fostered by the
great and even spectacular events and discoveries of the time.
Uranus was discovered in 1781, and was an object of great
popular as well as scientific interest. Neptune was not found
until 1846, by the labors of Leverrier. and Adamj, but the
nature of the problem involved was by no means original with
them, and had been in the minds of astronomers for more than
12 THE ANCESTRY OF THE HARVARD OBSERVATORY
20 years. Several satellites, or moons, had also been discovered
in the solar system; four minor planets were discovered early
in the nineteenth century; comets of great brilliancy, especially
Halley's comet at the return of 1835, fanned the public interest;
the meteor shower of 1833 was a most spectacular event.
The total eclipse of the sun in 1806 was the means of turning
the life of William Cranch Bond into astronomical lines. The
first authoritative determination of the distance of a star was
made in 1837 for 61 Cygni. These various events made a
strong appeal to all intelligent men.
Just when the idea was first conceived of establishing an
astronomical observatory for Harvard University cannot be
determined with certainty. It was probably not later than
the closing years of the eighteenth century, for:
As early as the year 1805, we find Mr. John Lowell, at that time residing
in Paris, consulting with the French astronomer, Delambre, on the subject
of astronomical observatories, and procuring from him written instructions
in regard to suitable buildings and instruments. The information thus
gathered was transmitted to Mr. Webber, at that time Hollis Professor
of Mathematics and Natural Philosophy in Harvard College, from which
we conclude that the purpose of erecting an observatory was then under
serious consideration by friends of the College. It does not appear,
however, that any official action was taken upon the subject at that time.
It was ten years later that the Corporation adopted active measures for
the promotion of this object, when, at a meeting of the President and
Fellows, held May loth, 1815, present, the President [Dr. Kirkland], Dr.
Lathrop, Hon. Christopher Gore, Judge Davis, Hon. John Lowell, Judge
Phillips, it was " Voted, That the President, Treasurer, and Mr. Lowell,
with Professor Farrar and Mr. Bowditch, be a committee to consider
upon the subject of an observatory, and report to the Corporation their
opinion upon the most eligible plan for the same and the site." 13
This was probably the first corporate act passed in the
United States having for its object the establishment of an
astronomical observatory.
A subcommittee consisting of Professor Farrar and Dr.
Bowditch was afterward appointed to attend especially to
the subject. Mr. William Cranch Bond, a Boston clock
13 H. A., i, ii, 1856.
THE HARVARD OBSERVATORY FIRST PLANNED 13
maker and amateur astronomer, was about to make a trip to
Europe, and, on June 23, 1815, he was requested by the chair-
man of the Committee, Professor Farrar, to make a careful
study of the Greenwich Observatory, and :
Also, inquire of Troughton the price of an eight-foot transit instrument
of the best construction for an observatory, and the price of an eight-foot
circular instrument of the kind lately made for the Observatory at Green-
wich, and how soon these two instruments can be completed upon being
ordered. The prices of the best clocks for observatories, and how soon
one can be made, and the price of a heliostatic movement for a telescope.
I would observe further, that, with regard to the sort of information
which we wish you to bring with you, in order to answer our purpose, it
must be such as to enable you or some other person to superintend and
direct in the erection of an observatory. 14
These instructions were faithfully carried out by Mr. Bond,
and on his return he had a model dome constructed at his own
expense, on the same plan as that later used for the large dome
of the i5-inch refractor. A discussion of the mass of informa-
tion collected by Mr. Bond and that received from other
sources showed that the expense of establishing and maintaining
a well-equipped observatory would greatly exceed the estimates
that had previously been made. An unsuccessful appeal to
some wealthy friends of the plan proved that the time was not
ripe for its execution.
The design was revived in 1822, and the same committee examined
various positions in the vicinity of the college, for the purpose of selecting
the most suitable for an observatory. A report was made very favorable
to a position in that vicinity, on land owned by Edmund Dana, and an
authority was given to purchase two acres and a half for that purpose.
The negotiations, however, failed, and further proceedings were postponed.
In October, 1823, John Quincy Adams, then Secretary of State of the
United States, addressed a letter to a member of the Corporation, urging
that a building should be erected, without waiting for instruments from
Europe, and recommending that the site nearest the College should be
selected, even should it occasion some addition to the expense; proximity
to the College being, in his judgment, important to the health and comfort
of both the professor and the students, as the night and the winter are
" Ibid ., iii.
14 THE ANCESTRY OF THE HARVARD OBSERVATORY
the time and season specially adapted to astronomical observations.
Mr. Adams strongly recommended a subscription to be opened for the
purpose, and, upon condition that the requisite sum should be raised in
two years, authorized a thousand dollars to be put down on his account,
but requesting his name to be concealed. The attempt, however, did
not succeed. In October, 1825, the time limited in his former subscription
having expired, he wrote again, to the same member of the Corporation,
on the subject, urged a renewal of the attempt, and renewed his offer of
one thousand dollars, on the same conditional limitation of two years.
About this time, an address to the public was prepared and published, and
a subscription opened, but in the result proved insufficient. 16
President Kirkland, in his Annual Report for 1825 to 1826
to the Overseers of Harvard University, made a strong appeal
for the establishment of a professorship of astronomy at the
University, together with an astronomical observatory, stating
that such action would establish the first observatory in the
American hemisphere. This appeal appears to have met with
no response.
Foundation of the Harvard Observatory. For 13 years
the hope of establishing an observatory lay dormant. The
events that finally led to their realization are best related in
the words of President Quincy, who had a deep interest in the
plans, and who wrote in 1840, before the Observatory had
been removed from its original site:
No further active endeavor (since 1825) was made for this object until
the autumn of 1839. During the interval, the land formerly selected as
a site for the observatory had been purchased, and thus one great requisite
for success was attained. The house on this land was also large and
commodious; the site for the observatory the best in the immediate
vicinity of the College, and satisfactory. When the subject was com-
municated to the friends of the design, their opinion was unanimous, that
the opportunity was highly favorable for its commencement. Funds
adequate to the buildings immediately requisite having been readily
obtained, the house was furnished with all the additions that were needed
to fit it for its intended purpose.
The Observatory has now at its command, from the College apparatus
and the instruments belonging to Mr. Bond, a transit instrument and
16 Josiah Quincy, op. cit., 2, 567, 1840.
FOUNDATION OF THE HARVARD OBSERVATORY 15
variation transit, by Troughton and Symms; an astronomical clock, one
refracting and two reflecting telescopes; an astronomical quadrant, by
Bird; Gauss' magnetometer; a small transit, by Bird; a quadrant and
sextant, with chronometers, thermometers, barometers, hygrometers,
dipping and variation needles. To render the observatory as efficient
as could be desired, there is wanted a refracting telescope equatorially
mounted, a mural circle, and a large transit instrument. These, it cannot
be questioned, will soon be supplied in some form, by the liberality of the
public or individuals, as soon as the advance already made towards a
sufficient apparatus for an observatory shall be understood and realized.
Although the apparatus possessed by Mr. Bond was excellent, and
sufficient for the observations in which he was engaged in connection
with the Exploring Expedition, yet it was not expressly adapted to the
purposes indicated by the Royal Society of Great Britain, in their address
to the several scientific societies in Europe and America, on the subject
of a conjoined and contemporaneous series of observations on meteorology
and the elements of the magnetic power; and the American Academy of
Arts and Sciences, in Boston, being desirous to cooperate with the Royal
Society of Great Britain on this subject, and to aid, also, the exertions in
this direction of the Corporation of Harvard College, appropriated one
thousand dollars for the purchase of the requisite instruments, in con-
formity with the suggestions and request of the Royal Society, deposited
them in the rooms of the University, and placed the whole at the disposal
of Professor Lovering and Mr. Bond, and have thus enabled the College
early to become one of the few magnetic stations yet established on this
side of the Atlantic.
A regular series of observations is now, and for these eight months
has been making, by Mr. Bond, and Professor Lovering, with the valuable
assistance of Benjamin Peirce, the University Professor of Mathematics,
a publication of some of which, it is expected, will soon commence, and
be afterwards regularly communicated to the public. 16
Thus did the Harvard College Observatory come into being.
Its future was placed in the hands of William Cranch Bond.
The time and manner of the engagement of Mr. Bond by the
Corporation can also best be told in the words of President
Quincy:
In October, 1839, the Corporation were informed that Mr. William
Cranch Bond was engaged, under an appointment and contract with the
Government of the United States, with a well-adapted apparatus, in a
w Ibid., p. 567-
1 6 THE ANCESTRY OF THE HARVARD OBSERVATORY
series of observations on "meteorology, magnetism, and moon-culmina-
tions, as also upon all the eclipses of the sun and moon and Jupiter's
satellites," in connexion with those which should be made by the officers
of the expedition to the South Sea, commenced in 1838, under the authority
of Congress, for the determination of longitude and other scientific pur-
poses. Being also apprized of the reputation sustained by Mr. Bond as
a skillful, accurate, and attentive observer, they made arrangements
with him, with the consent of the Government of the United States, for
the transfer of his whole apparatus to Cambridge, appointed him Astro-
nomical Observer to the University and took measures to raise by sub-
scription a sufficient sum to erect such buildings as were immediately
required. 17
11 Ibid., p. 391.
CHAPTER II
THE OBSERVATORY AT THE DANA HOUSE
FOR about four years the newly established Observatory
remained at the Dana House. The main building, more
recently referred to as the Dana-Peabody House, was probably
built by Thomas Foster, who purchased a part of the old
Dana estate; it still stands in the southeast part of the College
inclosure near the corner of Quincy Square and Quincy Street.
It was occupied as a dwelling by Richard H. Dana, the poet,
from 1822 to 1832, and later by President Felton, and Pro-
fessors Peabody and Palmer. A cupola on this house was
provided with a dome for the use of the principal observing
instrument, a reflecting telescope. The instruments then in
the possession of the College were useful for teaching rather
than for research.
The Early Astronomical Equipment. Bond brought with
him from Dorchester his own instruments with which he had
for some time been making observations for the Government
of the United States. These observations were continued in
Cambridge. His instruments included two small telescopes a
reflector and a refractor a 2%-inch transit instrument made
by Troughton and Simms, and two excellent clocks. Bond
and his family lived in the Dana House and one room was
occupied by an astronomical clock, a sidereal chronometer,
a standard barometer, and three auxiliary barometers. The
transit instrument was placed in an adjacent building made
especially for it on a foundation of massive construction,
according to Bond's usual methods. A meridian mark was
placed on a stone pier of solid masonry on the western slope
of Great Blue Hill, a distance of 58,520 feet, or a little more than
1 1 miles from the observatory. In the direction of the meridian
17
1 8 THE OBSERVATORY AT THE DANA HOUSE
it proved necessary to purchase the privilege of tunneling a
neighboring building in order to obtain a clear view of the mark.
The stone pier served its purpose admirably, but it has now
disappeared.
Two small rooms were constructed to the west of the transit
instrument for the continuance of the observations of magnetic
declination which Bond had been making for some time at his
Dorchester observatory. Another building was placed to the
north of the transit instrument for the use of the Lloyd magnetic
apparatus provided by a grant of the American Academy of
Arts and Sciences. These magnetic observations were made
under a cooperative plan proposed by the Royal Society of
London. The apparatus consisted of three magnetometers,
one for declination, one for horizontal force, and one for vertical
force. The details of the arrangements may be found in the
Annals of the Observatory. 1
During the years 1840 to 1842, Bond continued the observa-
tions begun at Dorchester in connection with the geodetic
work carried on by the Government of the United States.
Aside from this, the work of the Observatory was chiefly
magnetic and meteorological. The magnetic observations,
made in cooperation with other observatories in different parts
of the world, were carried on for three years, but they proved
to be extremely engrossing and interfered seriously with any
attempt to initiate new astronomical observations. Further-
more, the equipment was unsuitable for astronomical investiga-
tions. Bond was assisted in the execution of his plans by his
sons, William C. Bond, Jr., and George P. Bond, and also by
an organization of students styling themselves "The Meteoro-
logical Society of Harvard University." No salary was paid
either to Bond or to his assistants. Joseph Lovering, Hollis
Professor of Mathematics and Natural Philosophy, and
Benjamin Peirce, Perkins Professor of Mathematics and Natural
Philosophy, both took a deep interest in the beginnings of the
Observatory.
1 H. A., I, vi-xiv, 1856.
THE NAMING OF THE OBSERVATORY 19
The Naming of the Observatory. No definite name was
chosen for the Observatory for a number of years, although
several were proposed. It was even suggested at one time
that the institution, which after its foundation was usually
referred to as "The Observatory at Cambridge/' should bear
the name of some hoped-for benefactor, who might Suitably
endow it. There can be no doubt, however, that its founders
intended it to be associated with Harvard University.
The Observatory has long been popularly known as "The
Harvard College Observatory," or simply as the " Harvard
Observatory." An observatory is usually understood to
be an astronomical institution, but the existence of a meteoro-
logical observatory as a department of Harvard University
makes desirable the use of the prefix "Astronomical." The
Statutes passed in 1849 declare that the name shall be
"The Astronomical Observatory of Harvard College" still the
official title, although, since 1780, Harvard has held the rank
of a university.
In their report for 1851, the Visiting Committee, including
such distinguished men as Josiah Quincy, William Mitchell,
Robert T. Paine, David Sears, J. Ingersoll Bowditch, and
Francis Peabody, proposed that the name be modified by
changing the word "College" to "University":
To an Observatory which has, from the nature of its objects and duties,
a necessity of frequent intercourse with foreign seminaries, it is far from
unimportant that the most comprehensive name, and that by which it
is best known in Europe, should be retained. Your committee, therefore,
respectfully suggest, if it shall not be deemed advisable that the Observa-
tory should be hereafter, as it has been heretofore, designated by the
name of the city in which it is located, that it be permitted to take the
name of The Observatory of Harvard University.
No attention seems to have been paid to the proposal.
Although the Observatory is in reality a department of Harvard
University, the retention of the word "College" in its name
appears to be consistent with the official name of the Corpora-
tion of Harvard University "The President and Fellows of
Harvard College."
20 THE OBSERVATORY AT THE DANA HOUSE
Standing of the Observatory in the University, The
relations between the College professors and the newly
appointed "Astronomical Observer " were for several years ill
defined and uncertain, as may be inferred from numerous
letters written by persons of influence, as well as by acts of
the Corporation. In 1839, * n the official report of the agree-
ment with Bond by action of the Corporation, it is stated that
the southwest room of the Dana House is reserved
... as an observer's room, to be used in common by the said Mr. Bond
and the Professor of Natural Philosophy for the time being in Cambridge,
and the chamber over the same, together with the small room adjoining,
for the exclusive use of said professor.
Sometimes the name of the professor preceded that of Bond.
For example, President Quincy, in 1840, referring to the use
of the magnetic instruments given by the American Academy,
wrote: "And placed the whole at the disposal of Professor
Lovering and Mr. Bond."
Such an arrangement evidently gave opportunity for friction,
but no complaint seems to have been made by Mr. Bond, one
of the most unassuming of men. The uncertainty was still
present in 1845, when the site of the new Observatory was
about to be occupied. This is apparent from a letter addressed
to President Quincy by John Quincy Adams containing vari-
ous recommendations for improving the efficiency of the
Observatory:
4th. The appointment of an Observer and one Assistant, a measure
indispensable to make the whole establishment effective for the purpose
of continuous observation. In the first instance, it is very important
and desirable that these offices should be conferred upon Mr. Bond and
his son, but as a permanent institution, it seems that provision should
be made for a regular succession to these offices. That the mode of
their appointment, the occasions of vacancy, the tenure of their offices,
their right of occupation and custody of the buildings, both dwelling
house and Observatory, and of the adjoining grounds, should be regulated
and prescribed. That the line of division between the duties of the
Observer, and those of the Perkins Professor of Astronomy and the Mathe-
matics, should be accurately drawn. That the extent to which the
THE OBSERVATORY AND THE PUBLIC 21
Professor shall have a right to the use of the instruments and of access
to the Observatory, for the purposes of instruction in his department to
the students of the University, should be clearly defined. Whether
some liberty of occasionally assisting the Observer in making observations
may be indulged to students, whose inclinations may take a special
direction to the study of physical astronomy, and whether the teaching
of the use of the instruments to all students of the higher classes may not
be included among the joint duties of the Professor and the Observer.
Mr. Adams foresaw clearly the problems which would
arise later. In 1849, the Statutes of the Observatory were
passed, which use the term "Director," in place of " Astronomi-
cal Observer," and give to him entire authority over the
details of the Observatory equipment and work, subject only
to the authority of the governing boards of the University
The Observatory was thus wisely made a distinct department
of the University, with research as its chief duty.
The Observatory and the Public. The policy of the
Observatory in regard to teaching and service to the public has
varied greatly from time to time, under different directors and
presidents of the University. Perhaps the suggestions of Mr.
Adams represent a wise and conservative course of action.
As chairman of the Visiting Committee in 1847, he advised in
his report that a plan be provided:
For the occupation and employment of the Observatory in both its
capacities as a constituent department of the University, for the instruc-
tion of youth and as one of the towers of human science erected by a
spontaneous and sympathetic consent of civilized nations, to extend by
constant observation and calculation the knowledge of the physical
universe.
For many years after the installation of the " Great Tele-
scope," 2 much time and effort were expended in entertaining
the public. The popular demand for the privilege of using
the telescopes has always been much greater than the Observa-
tory could satisfy without too great interference with its
scientific work. All concessions of this sort have reduced the
2 See p. 26.
22 THE OBSERVATORY AT THE DANA HOUSE
scientific output of the members of the staff, and sharp restric-
tions have unfortunately been necessary. The problem could
best be solved by a special endowment for the teaching and
entertainment of the public, which would thus be carried on
more satisfactorily, and without interfering with the scientific
work of the Observatory. Such a plan was first proposed by
George P. Bond, second director of the Observatory, in 1860,
and the need of some arrangement of the kind has been generally
recognized ever since.
In recent years, under the direction of Dr. Shapley, a closer
cooperation has been effected with the teaching staff of the
University, and the opportunities for advanced astronomical
study have been much extended. A series of "open nights"
has also been introduced at the Observatory, for which tickets
are distributed, in the order of application, to the public. On
these nights visitors have the opportunity to observe some
celestial object or objects in the telescope, to see the illuminated
photographs of stars, nebulae, comets, and other objects, and
to listen to brief lectures on astronomical subjects. The
Observatory has also given much assistance to the American
Association of Variable Star Observers and to the Bond Astro-
nomical Club, societies largely composed of amateur scientists
and the scientifically interested public.
CHAPTER III
GROWTH OF THE PRESENT OBSERVATORY
IT was clear to the founders of the Dana House Observatory
that the equipment and arrangements were of a provisional
nature. The institution was ill equipped, and work was
carried on entirely by volunteer observers; but the University
then had no further available funds. If the Observatory
was to take a position at all in keeping with the spirit of its
founders and the traditions of Massachusetts and the Uni-
versity, some great impulse was needed to arouse the public
interest. Otherwise, like most of the other observatories
founded at about the same time in different parts of the United
States, though it might enter upon its task with enthusiasm,
it would rapidly sink as a center for astronomical research, into
a condition of comparative uselessness.
Endowment of the New Observatory. The heavens
themselves furnished the inspiration that quickened the public
interest. In March, 1843, a comet of surpassing size and
splendor appeared, and attracted intense interest. Appeals
were made to the " Observatory at Cambridge" for observa-
tions and information. Unfortunately (or perhaps fortu-
nately) the Observatory could not satisfy the demand, for it
possessed no instrument with which positions of the comet
could be accurately determined. Inspired by the remarkable
celestial phenomenon, and impressed by the inadequacy of
the equipment at the Observatory, a few men held a meeting
in Boston at the office of Mr. J. I. Bowditch, always a friend
of the Observatory, to consider means of providing new instru-
24 GROWTH OF THE PRESENT OBSERVATORY
meeting of citizens in order to discuss a plan for obtaining
for the Observatory an equatorially mounted telescope of the
highest quality. This gathering took place at the rooms of the
Boston Marine Society, and was attended by many men of
scientific interests and abundant means. Abbott Lawrence
acted as Chairman, and John Pickering, Professor Peirce,
William Appleton, and S. A. Eliot made addresses. A com-
mittee was formed to obtain subscriptions, and another com-
mittee, to prepare a report. At this meeting, also, David
Sears, through President Quincy, indicated his wish to give
$5000 for the erection of a tower for the reception of a telescope,
provided others would subscribe $20,000 for the purchase
of the telescope. This proposal was referred to as " munifi-
cent/' and indeed it was munificent in comparison with what
had already been given to the Observatory; also, when the
standards of that day are taken into consideration, the sum
proposed was really large. Materials and labor were then
vastly cheaper than now; and the salary of the leading professors
at the University was from $1500 to $1800 a year. In the
College catalogue for 1839 to 1840, the estimated necessary
expenses of a student for the college year at Harvard, including
tuition, fees, books, room, and board, were placed at $195.
The $20,000 needed to make good the $5000 offered by Mr.
Sears was promptly contributed by citizens of Boston, Salem,
New Bedford, and Nantucket. No restrictions of any kind
were imposed upon the gifts; the telescope, when obtained, was
to be devoted to the best interests of astronomy. The amount
subscribed was sufficient to obtain the best telescope which
could be bought at that time; and it only remained to select
a desirable form of instrument and the best maker.
Between a refracting and a reflecting telescope, the choice
was wisely made in favor of the former. The reflecting
telescopes of that day were much inferior to the refractors
both in definition and in convenience of manipulation. An
equatorial form of mounting was also chosen, such as had been
found extremely satisfactory for the refracting telescopes
OBSERVATORY TRANSFERRED TO PRESENT SITE 25
already in operation at the Dorpat and Poulkova Observatories.
After consultation with astronomers and opticians in various
countries, the contract was awarded to Merz and Mahler of
Munich, the successors of Fraunhofer. By the terms of the
contract, two lenses were to be made of 15 inches aperture,
of a quality equal to that of the lens recently made for the
Poulkova Observatory. A choice was to be made of one of
these, with the privilege of rejecting both, should the quality
be considered unsatisfactory.
The Observatory Transferred to the Present Site.
It had been recognized for some time that the Dana House
location was unsuitable for an observatory of the first class-
such as was now contemplated. After a careful investigation,
a new site was found which promised to be satisfactory. It
was a part of the Craigie estate, known at the time as " Summer-
house hill," and without doubt it was the best site in the
vicinity of the University. The highest part rises about 50
feet above the neighboring lands, and is 80 feet above tidewater.
At that time the Craigie estate was for the most part open
country; and with no electric lights and no street cars or heavy
trucks, the situation was as favorable as could be desired.
The immense growth of Boston and Cambridge, which after
three quarters of a century has again made the surroundings
of the Observatory very unfavorable for astronomical observa-
tions, could hardly have been foreseen.
Fortunately the University was able to purchase a sufficiently
large area in the most desirable location. The land originally
acquired for the Observatory, and set aside for its use, was
between six and seven acres in area, and was bought at a cost
of $4100.
In a report by the Treasurer of the University for 1845 to
1846, it is stated that:
The Observatory account stands charged with a balance of more than
nine thousand dollars against it. Of this about six thousand and five
hundred dollars have been spent on the buildings and grounds. A
26 GROWTH OF THE PRESENT OBSERVATORY
further sum remains to be paid on account of the dome, which is not yet
completed; and thirteen thousand and five hundred dollars are to be
expended on the large telescope, and a transit circle which has been ordered
from London. So that on the whole, the College will have spent on the
Observatory nearly double the sum that it has received.
The whole expense up to this time had been about $50,000.
The observer's house and a considerable part of the Observa-
tory buildings had been completed by September, 1844, and
the instruments were removed from the Dana House site to
their new positions. The 4-foot transit instrument and the
small out-buildings occupied by the magnetic apparatus were
removed to a location about 60 feet north of the new main
building. The following winter, a transit instrument made
by Troughton and Simms and imported by the Government
of the United States was mounted in the prime vertical and
was employed in observing the zenith distances of stars for the
determination of the latitude of the new Observatory, according
to the method of Bessel. The use of this instrument was
granted by Lieutenant-Colonel James D. Graham, of the North-
eastern Boundary Commission of the United States.
A small refractor was mounted on the grounds in December,
1844. It was replaced later by one somewhat larger. With
these telescopes observations were made, during 1845 an d 1846,
of eclipses, comets, and sunspots.
Installation of the 15-inch Refractor. In May, 1846,
Messrs. Simms and Cranch, the London agents appointed
for the purpose, visited Munich and made an examination
of the two lenses for the large refractor, which were then ready
for inspection. They found one of the lenses of better quality
than the other, and apparently satisfactory in every respect.
The tests which were applied are described in full in Harvard
Annals, I, cix. They were the best which the agents could
make under the circumstances, which, however, did not permit
an examination of any celestial object. The better lens was
accordingly accepted and forwarded to Cambridge. Its
quality proved to be excellent. After more than three quarters
ADDITIONS TO THE EQUIPMENT 27
of a century, during which the building and mounting have
become somewhat antiquated, the lens itself remains in splendid
condition. This excellent performance constitutes a tribute
not only to the makers, but also to the long line of observers
who have used and cared for the lens during many years.
The object glass of the " Great Refractor " was received at
Cambridge on June n, 1847, an ^ on June 23 and 24 it was
placed in its proper position, the mounting having already
been prepared for it in the Sears Tower. One can readily
imagine with what interest and even anxiety it was first
turned toward the sky. Added to some uncertainty as to the
perfection of the lens and its equipment was the fact that the
public regarded the telescope as the most efficient in the world
and expected notable observations and discoveries through its
use. The first objects examined were the Great Nebula in
Andromeda and the Orion Nebula. The results of these and
many other tests were most satisfactory. Public expectations
were soon satisfied by the discovery of the inner dark ring of
Saturn, known as "Bond's Ring," and by other striking
observations, some of which are described in later chapters.
Additions to the Equipment. Next in importance to the
large refractor, in the equipment of the new Observatory,
was a transit circle, made by Mr. Simms, of Troughton and
Simms, of London. This instrument was received in 1848
and was mounted in the east wing. It had a circle 4 feet in
diameter, and an objective, 4^ inches in diameter and 5 feet
in focal length. It appeared to be as perfect an instrument
as could be obtained in those days; but an injury, which appa-
rently was received during its shipment from London, affected
the divisions of both circles, and prevented its use for the
measurement of absolute declinations. It was used, however,
for many years, as a transit instrument, for the observations
of time-stars, and for the determination of right ascensions.
The west wing of the Observatory was designed for the
use of a transit instrument, and also contained a small dome
28
GROWTH OF THE PRESENT OBSERVATORY
for a refractor of moderate size, rooms to meet the needs of
computors, and the library. This wing was not finished until
1851.
A comet-seeker, presented by Mr. J. I. Bowditch, proved
a valuable addition to the equipment. With it, George P.
Bond discovered independently 10 comets, although it later
appeared that most of them had been seen earlier in Europe.
This was before the establishment of telegraphic communica-
tion between Europe and America.
North
West
FIGURE I.
Plan of the buildings and instruments of the Harvard Observatory as given by
William C. Bond in the first volume of the Annals, 1856.
The appearance of the completed main building of the new
Observatory is shown in the illustration on the frontispiece,
taken from a woodcut which appeared in the Boston Transcript
in 1852. The view is from the southeast, near the corner of
Concord Avenue and Bond Street. The general plan of the
buildings and instruments is given in Figure i taken from the
first volume of the Annals. The director's residence was at E,
the recently acquired transit circle at B, the prime-vertical
transit at C, the old transit circle at /, and the small equatorial
at F. Minor instruments were placed in various positions in
ADDITIONS TO THE EQUIPMENT 29
the main building, or in small isolated shelters. At the center
of the plan, at A, in the Sears Tower, was, and still remains,
the large refractor.
Many details of the installation of the Observatory are
given by William Cranch Bond in Volume I of the Annals
of the Observatory. It seems unnecessary in this place to
give more than a brief summary of them. Although much work
was done with other instruments, the real interest of the public
and of the astronomers was associated with the large equatorial
telescope. The dome containing it is still the central and
striking feature of the buildings. The Sears Tower is 32
feet square, with solid foundations and walls. These are
square on the outside, but are brought into a circular form
within, on the first floor, with recessed corners. The pier
occupies the center of this room, generally referred to as the
"Rotunda." In recent times the pier has been surrounded
by book shelves. In the dome room above are recesses similar
to those below, and on the north, east, and west sides of the
dome, doors open upon iron balconies which have proved very
useful for miscellaneous observations. The dome itself, a
hemisphere in form, is 30 feet in diameter, and rests on spherical
iron balls freely moving in grooves both above and below. By
means of suitable mechanical contrivances the dome, which
weighs 14 tons, can be revolved by one person through an entire
circuit in about half a minute. A suitable opening was pro-
vided, extending from three degrees beyond the zenith to three
degrees below the horizon, and covered with an arrangement
of movable shutters.
The telescope was mounted on a pier of most substantial
workmanship, after the usual methods of Bond. The founda-
tion was placed 26 feet below the natural surface of the ground.
Upon a cement base, the pier was constructed of large blocks
of Quincy granite. It was made entirely solid to the height
of n feet above the foundation. The floor of the dome is
reached at the height of 33 feet, where the pier is surmounted
by a circular granite capstone, 10 feet in diameter and 22 inches
30 GROWTH OF THE PRESENT OBSERVATORY
in thickness. Upon this stone rests a granite pedestal, weighing
ii tons, to the top of which the bedplate of the equatorial
mounting is secured. The pedestal is referred to by Bond as a
"tripod," from the fact that it was constructed to rest on the
capstone by three bearings, so situated in regard to the center
of gravity of the whole block and telescope that each bearing
supported a nearly equal share of the weight. This was a
favorite method of Bond, who used it in all his piers. The bear-
ings were rounded protuberances. This method gave the utmost
steadiness, and permitted an easy change of position for adjust-
ment of the telescope.
In the equipment of the dome and telescope, Bond not only
made use of all the information which he had obtained abroad
at various European observatories, but brought to the problems
his own original ideas, derived from many years of practical
work. Everything was carried out with his characteristic
thoroughness and mechanical skill, as is shown by the observing
chair for the large refractor, which was constructed under his
direction. Seated in a comfortable chair, the observer, by
the rotation of an adjacent wheel, can elevate or lower himself
to any desired altitude. The position of the observer in
azimuth can be arranged at will by means of a circular track
on which the whole apparatus revolves. This observing chair,
although somewhat cumbersome and out of date, has served
its purpose well, and is still in use. So admirable was its
construction that it gives no evidence of being worn out after
many years of active service.
The Phillips Bequest. With the opening of the new
Observatory, the question of salaries for the observers became
urgent. Until 1846, no salaries were paid. It was obvious
that such a system could not long continue. Since the Univer-
sity had no funds for the purpose, provision was made for two
years through the generosity of a few citizens of Boston.
In 1849, by the will of Edward Bromfield Phillips, the sum
of $100,000 was received by the Observatory. This was a
THE CAMBRIDGE ASTRONOMICAL SOCIETY 31
munificent bequest for that time. It opened up new possi-
bilities, and obviated much hardship and worry. Perhaps,
however, too much was expected from it. Section VII of the
Statutes of the Observatory states:
The salaries of the Director and Assistants shall be fixed by the President
and Fellows, and be paid out of the income of the fund established for
this object by the will of the late Edward Bromfield Phillips. From the
income of the same fund shall be drawn such sums as, in the judgment of
the President and Fellows, shall be necessary or expedient for the purchase
of books and instruments, and fcr their repairs and preservation.
For some years after the enactment of the Statutes, this
Fund may have been able to supply the demands made upon it,
but later it was obviously insufficient to care for the great
growth of staff and equipment. Further endowments, however,
supplied other resources, and relieved the strain on the Phillips
Fund.
The Cambridge Astronomical Society. The growth of
astronomical institutions on the American Continent ran
parallel to the development of the science in Europe. The
Royal Astronomical Society, founded in 1820, had held monthly
meetings since its foundation. In 1854 the first forerunner
of the American Astronomical Society was founded at Cam-
bridge. The leading spirit in its foundation appears to have
been Benjamin Peirce, at the time Perkins Professor of Astron-
omy and Mathematics and head of the theoretical department
of the American Ephemeris and Nautical Almanac, then
located at Cambridge. Professor Peirce thought the Society
should be formed as a local body, but in such a way that it
might later become a branch of a national astronomical society,
the foundation of which he foresaw. The original records of the
recording secretary of the " Cambridge Branch of the American
Astronomical Society" are in the possession of the Harvard
Observatory.
The members of the Society were very carefully selected,
and the papers and discussions at the meetings were highly
technical. The sciences to be covered by the members of the
32 GROWTH OF THE PRESENT OBSERVATORY
Society were astronomy, geodesy, and mathematics. Professc
Peirce was chosen first President. Joseph Winlock, at the tin
a computer in the office of the American Ephemeris, was mac
Recording Secretary, and John D. Runkle, Correspondir
Secretary. Other distinguished members of the Society wer
Newcomb, Gould, George P. Bond, Hill, Oliver, Peters, Eas
wood, Kerr, Wright, and Safford.
Meetings were held each fortnight. The first took place c
January 24, 1854, and others followed with considerab
regularity until October 24, of the same year, when the sevei
teenth meeting occurred. The eighteenth, and, by the record
the last meeting ever held, took place on September 22, 185
The American Astronomical Society, first known as tl
" Astronomical and Astrophysical Society of America/' tl
establishment of which was predicted by Peirce in 1854, w<
begun in 1898, at a meeting of astronomers held at the Harvai
Observatory.
The First Directors; William and George Bond.-
William Cranch Bond, the first director of the Observaton
and the first to hold the Phillips Professorship of Astrononr
died in 1859, at the age of seventy years. He had been i
charge of the Observatory for about 20 years. The Universit
could have made no wiser choice of a leader for the establishmer
of the institution and for its control and encouragement durin
its early years.
On the death of William Cranch Bond, his son, George Phillip
Bond, was his logical successor. Even when a young boy h
had assisted his father in his observations, and in the work (
the new Observatory he had taken the leading part. H
familiarity with the needs and the activities of the institutioi
the abilities which he had already shown, and the scientifi
reputation which he had gained, made him the choice of th
Corporation, and he was appointed second director of th
Observatory, and Phillips Professor of Astronomy, in 1850
The only other candidate for the position appears to have bee
APPOINTMENT OF JOSEPH WINLOCK 33
Professor Benjamin Peirce, no doubt the ablest American
mathematical astronomer of his day, but with little or no
experience in observational astronomy. George P. Bond gave
a whole-hearted devotion to the interests of the Observatory.
Unfortunately, his health slowly failed, and he died in 1865,
at the early age of thirty-nine years.
Under the Bonds, whose lives and achievements are described
elsewhere in this volume, the Observatory gained an enviable
international reputation. The large refractor was kept con-
stantly busy in the observation of Saturn, Mars, and other
members of the solar system, of Donati's and other comets,
of the great nebula in Orion, and of other celestial objects. The
positions of faint stars were determined in a zone extending
from the equator to i oo', north declination. Much attention
was given, through the voluntary aid of Messrs. Whipple and
Black, of Boston, to a study of the application of photography
to scientific research; and George P. Bond, especially, clearly
foresaw the amazing possibilities of the introduction of photo-
graphic methods into astronomical investigation. During
all this time, in spite of the income of the Phillips Fund, the
want of money for badly needed developments was always
keenly felt. Assistants came and went, drawn by their interest
in astronomy and the reputation of the Observatory, and driven
away by their inability to exist on the salaries offered.
A year elapsed after the death of George P. Bond before the
appointment of his successor. During this interval, the Observ-
atory was in charge of Professor Truman H. Safford, who
applied himself chiefly to the preparation for the press of
additional volumes of the Annals. A large amount of unpub-
lished material had accumulated, and its reduction and publica-
tion were carried forward as rapidly as the limited staff and
inadequate income permitted.
Appointment of Joseph Winlock. Joseph Winlock, the
third director of the Observatory, began his term of service
in 1866, at the age of forty years. He had received adequate
34 GROWTH OF THE PRESENT OBSERVATORY
training, and had gained a wide experience in mathematici
and astronomical lines. He had held the positions of Professc
of Mathematics and Astronomy at Shelby College, Head of tt
Mathematical Department of the United States Naval Academ
at Annapolis, and member of the United States Naval Observe
tory at Washington. His interests lay especially in what hi
been known as the "old astronomy," or the astronomy c
position. His skill in mechanical appliances of all kinds w
unusual, and his energies were directed largely toward th
perfection of the equipment of the Observatory. Not satisfie
with the transit circle already in use, he arranged for the pu;
chase of a new meridian instrument of larger size and great*
perfection. With this new instrument William A. Roge]
began work on one of the zones of the international cooperati\
revision of the Durchmusterung, that between 50 and 55 (
northern declination.
Much effort was expended during Winlock's administratio
in the perfection of the time service, which furnished accurat
time for the people of Boston and vicinity. This service ws
made to provide a small but much needed addition to th
income of the Observatory. The large refractor was devote
especially to physical researches, and to the measurement c
binary stars. It was also employed in an unsuccessful searc
for new planets, and for the determination of positions c
asteroids and comets. Various spectroscopic studies of star!
of nebulae and comets, of the aurora, and especially of th
sun at the total eclipses of 1869 and 1870, were undertaker
During this period Professor Shaler of Harvard began a
investigation of the lunar surface, with the large refractoi
from the viewpoint of a geologist. Trouvelot also used th
same instrument for several years in obtaining numerou
drawings of various celestial objects. Meteorological observa
tions were regularly made.
Professor Winlock's activities were suddenly and unes
pectedly closed by his death at the age of forty-nine year
in June, 1875.
DEVELOPMENT OF THE OBSERVATORY 35
Development of the Observatory under Pickering.
Edward C. Pickering, the fourth director of the Observatory,
received his appointment in 1876, but he did not assume his
new duties until February i, 1877. During the interval,
Professor Arthur Searle was acting director of the Observatory,
and devoted the energies of the small staff to the preparation
for the press of several volumes of the Annals, in addition to
the usual astronomical observations.
Mr. Searle brought up to date the history of the Observatory,
begun by William C. Bond in the first volume of the Annals,
publishing this work in the eighth volume and including
elaborate diagrams of the Observatory grounds and buildings,
the various instruments, their piers, and the electrical connec-
tions, as well as the different clocks and chronographs. 1
In 1877, at the beginning of Pickering's administration,
the condition of the Observatory was that of an institution
struggling with insufficient income to support its staff, and to
find means for the publication of the accumulated observations
of preceding years. It is significant of his methods that once
he had begun work with the facilities already provided, Picker-
ing made repeated efforts to increase the income. He found
the Observatory equipped with two instruments of the highest
class for that time: the large equatorial refractor, and the new
meridian circle obtained by Winlock. It was extremely desir-
able that these instruments should be fully employed, and
at the same time that the results of the observations should be
prepared promptly for publication. Up to that time, only the
first eight volumes of the Annals had been published, with
the exception of Volume 4, Part 2, which was nearing completion
by Professor Safford, then at Williams College. By the close
of Pickering's directorship, the number of published volumes
of the Annals was approaching one hundred.
As a physicist, Pickering naturally directed the work of
the Observatory largely into astrophysical lines. Neverthe-
less, the work of the large meridian circle occupied the time
i H. A., 8, Part i, 1877.
36 GROWTH OF THE PRESENT OBSERVATORY
of one or more assistants and a corps of computers for nearly
40 years.
During Pickering's term of service, the endowment and
equipment of the Observatory were greatly increased. His
leading interest for many years was in the photometry of the
stars. At first, this was confined to visual observations, but
later became more and more photographic. A rare oppor-
tunity for spectroscopic researches was also utilized to the
utmost, chiefly by photographic methods. Toward the close
of his life, the completion of the Henry Draper Catalogue of
stellar spectra, the classification for which was done by Miss
Cannon, absorbed his attention. This catalogue, consisting
of nine volumes of the Annals, was nearly finished at the time
of his death. The photometric and spectroscopic researches of
Pickering's time are described in later chapters.
Some of the other problems which had a great development
during the directorship of Pickering were the discovery and
study of variable stars, novae, clusters, and nebulae, as well
as observations of comets and planets. The creation of the
library of celestial photographs, mainly of stars, containing
more than 200,000 original negatives, was a unique achieve-
ment, involving the foundation of the most valuable and
irreplaceable astronomical collection in the world.
In order to extend the researches to the whole sky, an
auxiliary southern station was established in 1890, under the
Boyden Fund, at Arequipa, Peru. This station remained in
active operation until the end of 1926, when it was removed
to Mazelspoort, near Bloemfontein, South Africa.
Professor Pickering died on the third day of February, 1919,
at the age of seventy-two years. He was Director of the
Observatory for 42 years, more than one half of the time since
its foundation in 1839.
During nearly three years following, the Observatory
was in charge of Professor Solon I. Bailey, whose chief endeavor
was to push forward as rapidly as possible the unfinished
researches begun during Mr. Pickering's administration. The
SHAPLEY CHOSEN DIRECTOR 37
staff at this time was large and able, and considerable progress
was made.
Shapley Chosen Director. The fifth and present director
of the Harvard Observatory is Harlow Shapley. He was
graduated from the University of Missouri in 1910, and took
the degree of Doctor of Philosophy from Princeton University
in 1913. While at Princeton, he was the author of an important
series of studies of eclipsing binaries. Called to the Mount
Wilson Observatory in 1914, he soon gained an international
reputation, especially from his researches on Cepheid variable
stars and globular clusters, and their relation to the structure
and size of the galactic system.
In November, 1921, Dr. Shapley was chosen by the Cor-
poration of Harvard University as the fifth director of the
Observatory. In command of the great accumulations of data
at Harvard, he has extended his investigations so as to include
many additional lines of observation and discussion, which
may be expected to throw light on the nature, distribution,
and motions of the different members of the visible universe.
CHAPTER IV
INSTRUMENTAL EQUIPMENT
THE development of modern astronomy has been intimately
associated with the invention and perfection of mechanical
aids. Without the telescope, the spectroscope, and other
astronomical instruments, comparatively small advance would
have been possible.
A large number of telescopes and various other instruments
have been in use at the Observatory during its history. A
list of telescopes is given at the end of the chapter; a brief
description follows of the most important instruments,
special attention being given to those which have peculiarities
in construction devised by members of the Observatory staff.
No attempt is made to explain the principles and construction
of standard instruments.
The Chronograph. The introduction of a satisfactory
astronomical chronograph, for recording observations made
with the meridian circle and other instruments, marked an
important advance in observational procedure. Its use soon
became almost universal in time observations for geodetic
work, as well as in more purely astronomical investigations.
The credit for the invention and perfection of a successful
chronograph was for a long time the subject of much con-
troversy. As usual in such cases the instrument was the result
of many attempts by many minds. As developed by the Bonds,
it was called by them the "spring-governor and electric clock."
The term " spring-go vernor" refers to the control mechanism,
and the electric current, which had recently come into use, was
a necessary element in its operation.
The first experiment for the determination of differences in
longitude by the electric telegraph appears to have been made
38
THE is-INCH VISUAL REFRACTOR 39
r Admiral Wilkes in 1844. Electric signals were used which
*re recognized by the ear. Later, similar attempts were
ade in various places until the method became standardized,
tie idea of an automatic current-interrupter occurred to W. C.
Hid early in 1848, according to his son, G. P. Bond. The
ea probably presented itself to others at about the same time,
ice in the same year O. M. Mitchel, at the suggestion of
alker, of the United States Coast Survey, constructed such
i apparatus. Various improvements were suggested by
hers. Lack of uniformity in the revolution of the cylinder
[ which the recording sheets were placed was the outstanding
(ficulty. The Bonds, by the invention of the spring-governor,
viated this difficulty. They constructed an instrument in
50 which was the first really satisfactory astronomical chrono-
aph. It was due to the efforts of W. C. Bond and his two
ns, Richard and George. It received the award of a gold
sdal at the Crystal Palace Exposition in England and soon
me into general use, replacing the old eye and ear methods.
In the Bond chronograph a sheet of paper is placed on a
Under which makes a complete revolution once a minute,
i the paper rests a pen, which is electrically connected with a
indard clock, and is drawn slowly in an axial direction along
e cylinder. By means of automatic signals, the pen makes
ch second a slight movement to one side. Time intervals
,ve thus been converted into space intervals. The distance
tween the successive second marks may be a centimeter, or
3re, a quantity readily divisible into hundredths. The
cord of the star's transit across the wires of a reticle is made
r an observer, who presses the key in the same electric circuit
ting on the pen. The sheet may be filed and discussed at
y time. 1
The 1 5 -inch Visual Refractor. This instrument played
e chief r61e in the early years of the Observatory. It has
achromatic lens of the usual form, consisting of crown and
H. A., I, Part i, xlix, clviii, 1856.
40 INSTRUMENTAL EQUIPMENT
flint glasses. The lens and mounting were constructed by
Merz and Mahler of Munich, Bavaria, the successors of Fraun-
hofer. The lens has an effective aperture of 15 inches and a
focal length of 22^ feet. The granite pier on which it was
mounted is constructed in the thorough and massive way
characteristic of the director, W. C. Bond. The mounting is
of the German equatorial form. The polar and declination
axes are of steel, and the telescope tube, of light wood and
paper strengthened by iron diaphragms. The exterior of the
tube was veneered with mahogany. Eighteen eyepieces were
provided, furnishing powers of from 100 to 2000 diameters.
The lens, the work of Merz, proved to be a most admirable one.
Certain features of the mounting, however, were found unsatis-
factory. Bond states that :
The arrangements of the divisions of both the declination and hour
circles are awkward, and the reading off of both attended with needless
trouble; the screw for adjusting the focus of the eye-pieces is incon-
veniently situated; and the clock for regulating the movement of the
telescope is disproportional to the other parts of the instrument, and toe
feeble, rendering it in cold weather nearly useless. 2
These faults were in large part corrected later by the Clarks,
who introduced changes and improvements which brought the
mounting and clockwork up to the standards of that time.
The i5-inch telescope, unsurpassed in its day, was installed
at the Observatory in 1847, as already described. Around it
cluster most of the tradition and sentiment of the early days ol
the Observatory. It was affectionately referred to as the
" Great Telescope." Bond called it "our incomparable tele-
scope." Great things were expected of it by its donors new
discoveries and improved views of known objects. Nor was this
expectation disappointed, although few spectacular discoveries
were made. For half a century it held its position as the
principal instrument of the Observatory until its importance
waned with the introduction of photographic instruments,
Although photographic work had been early undertaken with
2 Ibid., xxxi.
s
^
(/)
?
K
(f)
Q
w
S
H
PLATE IV. THE MERIDIAN CIRCLE.
TRANSIT INSTRUMENTS 41
this telescope by the Bonds, the lens, corrected only for the
visual rays, gave poor photographic definition, and the results
are to be regarded merely as experimental and exploratory.
Transit Instruments. The astronomical equipment of the
old Observatory at the Dana House, within the College grounds,
was largely the property of W. C. Bond, and included a small
transit instrument. For the new Observatory, a Troughton
and Simms transit circle was provided, as described in the
preceding chapter.
One of the chief concerns of Joseph Winlock, when he became
Director of the Observatory in 1866, was the acquisition of a
new meridian circle of the best class. After elaborate investiga-
tions at home and abroad, Winlock ordered a new instrument
from Troughton and Simms, the lenses for which, however,
were made by Alvan Clark and Sons. This meridian circle
had an object glass 8^ inches in diameter and of more than
9 feet focal length. The diameter of each of the graduated
circles was 3 feet. The collimating lenses were 8 inches in
diameter. Various modifications were introduced into this
instrument by the makers at Winlock's suggestion. The most
important of these were the shortening of the piers and the
relieving of undue pressure on the pivot bearings by a system
of levers with friction rollers. Stability was thus gained and
the graduated circles were brought entirely above the piers,
which were covered with glass cases as a protection against dust.
This large meridian instrument was not received and mounted
until 1870. It was placed in the west wing and for many years
thereafter was one of the most important instruments of the
Observatory. The observations of the Zone of the Astrono-
mische Gesellschaft, from +49 50' to +55 10', by Rogers,
and that from 9 50' to 14 10' declination, by Searle,
were all carried out with this instrument as described elsewhere.
Another meridian instrument of special interest was the
"Russian transit," or " broken transit," made by Herbst,
mechanician of the Poulkova Observatory, under the direction
42 INSTRUMENTAL EQUIPMENT
of Struve. It also was received in 1870, and was mounted
just west of the large meridian circle. It was a portable
instrument having a lens of 2% inches diameter and 33 inches
focal length. A prism placed at the middle of the axis reflected
the light to the eyepiece at one side. The instrument was
used for longitude determinations and other occasional observa-
tions, and for teaching. 3
The Photographic Doublets. Edward C. Pickering, with
the aid of William H. Pickering, began experiments in celestial
photography in 1882. The advantages of the doublet were
early recognized, and a long series of doublets of different sizes
have contributed much toward the results obtained at the
Observatory during the last 40 years. Among the most useful
of these instruments have been the 8-inch Bache, the 8-inch
Draper, the i6-inch Metcalf, and the 24-inch Bruce. The
donor's name has generally been used to designate these tele-
scopes. All four are of similar construction. The 8-inch
Bache lens was originally a Voigtlander portrait lens. It was
bought at secondhand and refigured by the Clarks. Each
combination of the doublet consists of a crown and a flint glass.
The refiguring of the lens was necessary not only to improve
the definition but to change slightly the focal length, making
it 114.6 centimeters, so that the scale of the photographs
became 2 cm = i, the scale of the Durchmusterung charts.
When the Bache telescope was sent to Peru in 1889, for
work on the southern sky, it was replaced at Cambridge by
another similar instrument called the " Draper 8-inch doublet."
Objective prisms were employed with both instruments for
obtaining photographs of stellar spectra. Supplemented by
the work of larger instruments, they have led to the discovery
of numerous novae, variables, asteroids, and nebulae, and have
provided many of the photographs involved in the Draper
Catalogues of stellar spectra.
3 An elaborate description of the buildings and equipment of the Observatory
from 1855 to 1876 was given by Searle in the Annals (8, Part i, 1876).
THE PHOTOGRAPHIC DOUBLETS 43
In 1890, Miss C. W. Bruce of New York gave the Observatory
3,000 toward the construction and maintenance of a large
photographic telescope. Telescopes with a single achromatic
lens, corrected for photographic light, were used at that time
for photographic work at nearly all observatories. The field
of good definition of such a telescope is comparatively small.
A doublet gives good definition over a region several times as
great. For any research, therefore, such as the charting of
stars, nebulae, and other celestial objects, much greater speed
is possible with a doublet than with a telescope of the usual
form, such as that constructed by the Henry Brothers for the
use of the Astrophotographic Congress. On this afccount
Pickering decided to use the Bruce gift for the construction
of a much larger doublet than had hitherto been made. The
result was the 24-inch Bruce telescope of n feet focal length.
In effect it was an enlarged 8-inch Bache. The scale of the
resulting photograph was i mm = i', or 6 cm = i.
The construction of the Bruce telescope was intrusted to
Alvan Clark and Sons, of Cambridgeport. It was completed in
1894 and after preliminary trials at Cambridge, was sent to the
southern station of the Observatory at Arequipa, Peru, where it
remained until the closing of that station in 1927. It has proved
to be of immense value in the work of the Observatory. The
mounting was originally of the open fork type, the telescope tube
being suspended at the end of a fork, as with smaller doublets.
This plan of mounting was unfortunate in the case of so large
and heavy an instrument, especially at the latitude of Arequipa,
since manipulation was made difficult and flexures were
introduced. For use at the new South African station, the
instrument is being remounted in the two pier arrangement.
Thus equipped and placed it may confidently be expected to
yield material of the highest value in the solution of the stellar
problems under investigation by the present director of the
Observatory.
Another doublet of special importance is the 1 6-inch Metcalf
telescope. The lens was constructed gratuitously for the
44 INSTRUMENTAL EQUIPMENT
Observatory by the late well-known amateur astronomer,
the Reverend J. H. Metcalf . The definition is especially good.
Valuable investigations have been greatly assisted by its use,
such as the charts of the Kapteyn Selected Areas and of the
Harvard Standard Regions for the northern sky, and the
photographs for the determination of the position of the moon.
Curved plates have been used with this telescope, the curvature
being produced in the telescope with the aid of atmospheric
pressure and an air pump. The field of good definition is thus
considerably extended.
The Draper and Boyden Refractors. These telescopes,
one in the northern and the other in the southern hemisphere,
are a pair of instruments by means of which any investigation
within their scope can be made to cover the whole sky.
The n-inch telescope was obtained by loan from Mrs.
Draper, in 1886, in order to extend the work of the Henry
Draper Memorial. Later it became the property of the
Observatory by gift. Originally it was a visual telescope,
made for Dr. Draper by Alvan Clark and Sons. It was adapted
to photographic work by the use of a suitable correcting lens.
To obtain the spectra of the brighter northern stars, from one
to four objective prisms were placed over the lens. Spectra
of the brightest stars were thus obtained having a length of
about 5 inches, which showed in some cases many hundreds
of spectral lines.
This instrument was used for many years at the Jamaica
station by W. H. Pickering for visual observations of different
members of the solar system. It has also been employed by
King for obtaining out-of-focus images of the brighter stars
for photometric determinations.
The i3-inch Boyden refractor, of unusual construction, has
proved to be an exceedingly useful instrument. The crown
lens is reversible, and its two faces have different curvatures.
In one position, with the two lenses nearly in contact, the
spherical and chromatic aberrations are corrected for the visual
THE POLAR EQUATORIAL 45
rays. When the crown glass is reversed and separated some-
what from the flint glass, the aberrations are corrected for
the photographic rays. The plan was devised by Edward C.
Pickering, in consultation with the Clarks. The same idea
was independently proposed by Sir George S. Stokes and Sir
Howard Grubb at about the same time. In spite of some
apprehension in regard to the outcome of this scheme, the
results in the case of the i3-inch were satisfactory both visually
and photographically. Visually, it has been used by W. H.
Pickering and Douglass for observations of planetary detail,
and by various observers for the measurement of double stars.
Photographically, it led to the discovery of cluster variables
by Bailey, and provided photographs of the spectra of the
bright southern stars, a study of which was made by Miss
Cannon.
The Polar Equatorial. An interesting instrument in
active use at the present time is the 1 2-inch polar equatorial,
the mounting of which was devised by Gerrish. For many
years Pickering, in his extension of the Harvard Photometry
to faint stars, used the lens as a part of the 1 2-inch horizontal
photometer. When the observations planned for that instru-
ment were completed, the lens was taken for the construction
of the polar telescope. The telescope itself is fixed in position,
and the images of the stars are brought into the field by a
movable mirror easily controlled by the observer. The axis
of the instrument is parallel to the axis of the earth; the observer
looks into the eyepiece in the direction of the south pole.
The telescope is placed on the south side of the west wing of the
main building, with the observing end brought into the window
of a room on the second floor. The observer thus works in a
comfortable room, always seated in the same place and looking
in the same direction. The whole northern sky is at his
command, with the exception of a small region near the north
pole. This telescope has been found very convenient for
various kinds of visual observations, especially of variable stars.
46 INSTRUMENTAL EQUIPMENT
The Meridian Photometers. Pickering, when he began
his visual photometry of the stars, found no suitable photometer
in existence and proceeded to devise such an instrument, in
consultation with Alvan Clark and Sons. For the measure-
ment of the brightness of the naked-eye stars, included in the
early Harvard Photometry, an instrument having lenses of
about 2 inches diameter was used. Later, for the extension
of this research, a larger instrument was constructed on the
same general principles. It will probably be sufficient to give
a brief description of the second and larger instrument, which
had lenses about 4 inches in diameter and was capable of
measuring the light of stars as faint as the ninth magnitude.
Like most of the visual photometers that have been used at the
Harvard Observatory, it was a polarizing instrument, although
the i2-inch meridian photometer devised and employed by
Pickering for the measurement of faint slars made use of
wedges and shades.
The 4-inch meridian photometer was provided with two
object glasses placed side by side with a silvered glass mirror
in front of each. The lenses were inclined slightly to each
other, so that the light from both was brought into a single
eyepiece. A double-image prism, placed near the eyepiece
and at a distance from the objectives nearly equal to their
focal length, divided the light received from each lens into
two pencils. The pencil of ordinary rays from one lens was
made to coincide with the extraordinary rays from the other
lens, and the other pencils were excluded from the field of view.
With one mirror the star used as the standard of comparison,
generally a or X Ursae Minoris for the northern sky, was brought
into the center of the field. The mirror was capable of the
small motion necessary to keep this star in the proper position.
With the other mirror, which could be rotated readily so as to
command the meridian sky from one horizon to the other, any
star when near the meridian could be brought into the field
near the image of the standard star. Their light was then
equalized by the revolution of a Nicol placed in the eyepiece.
PLATE V. THE 24-iNCH BRUCE TELESCOPE, AS NEWLY MOUNTED AT
MAZELSPOORT.
(Facing page 46)
PLATE VI. THE 6o-iNCH REFLECTOR, MOUNTED IN PECKER'S FACTORY AT
PITTSBURGH,
THE 60-INCH REFLECTOR 47
As the Nicol revolved, the light of one star increased while that
of the other decreased. Four different settings of equality were
usually made, although in special cases the number was larger,
the mean of all being regarded as one determination of magni-
tude. The observations were repeated on one or more nights.
Suitable scales enabled the recorder to adjust the mirror for
stars of any right ascension and declination, and to make
a record of the readings of equality. The instrument itself
remained in a fixed position, the observer facing east or west.
For bright stars readily recognizable the settings of the instru-
ment by the circles gave the desired star with small probability
of error. For faint stars, the identification was checked by
any catalogue stars which might be near. For zone work, the
observer passed from one star to the next by the differences in
right ascension and declination.
Pickering also devised various polarizing photometers for
the photometric work carried on during many years, chiefly
by Wendell, with the 1 5-inch refractor. The principles
involved in their construction were somewhat similar to those
of the meridian photometers, but with great differences in
the details.
The 6o-inch Reflector. The Observatory obtained by
purchase in 1904 the 6o-inch reflecting telescope formerly used
by Common, of England. With this instrument Pickering
planned to extend the Harvard visual photometry to as faint
stars as possible. Much time and labor were spent in fitting
it for such observations. Owing to difficulties inherent in the
telescope and its mounting, however, the definition of the stars
was far from satisfactory. At about this time, also, the rapid
development of the photographic photometry of the stars made
a further extension of such work by visual methods less desira-
ble. Little use was made, therefore, of this telescope, although
some investigations were undertaken for the determination
of the total intensity of stellar radiations, a field for which its
great light-gathering power seemed to render it well fitted.
48 INSTRUMENTAL EQUIPMENT
Dr. Shapley, in the plans for the extension of his researches
into the extent of the visible universe, needed an instrument
of greater power than any of those in use at the Observatory.
One of the Common mirrors provided the glass for the mirror.
It was found to be well suited to the purpose and was refigured.
A mounting is being constructed (1927) by J. W. Fecker,
successor to Brashear and McDowell. The new reflector will
be sent to the station in South Africa; it will be the largest teles-
cope in actual service in the southern hemisphere. The
mounting is to be of the two pier type arranged for use in both
the Newtonian and modified Cassegrainian combinations.
The great need of such an instrument is clearly set forth in
the eighty second Annual Report of the Director:
The Harvard Observatory has carried on fundamental surveying work
in the southern skies for thirty seven years, attacking the numerous
problems in a comprehensive manner, but seldom analytically. For
example, the visual brightness, spectral classification, and variations in
light have been studied for thousands of stars: a score of new stars have
been found on plates made at the Boyden Station; some ten thousand
nebulae have been discovered; and surveys of double stars, star clouds,
gaseous nebulae, and star clusters have been products of the systematic
work with the several photographic refractors. But searching analyses
of special objects such as the Magellanic Clouds, globular clusters, gaseous
nebulae, and individual stars have generally been impossible. The rapid
photographic refractors and patrol cameras are suitable for the funda-
mental work and their use will be continued unabated, but a large well-
equipped reflecting telescope is necessary for the special analytical studies.
Miscellaneous Instruments. Several other instruments
deserve special mention. The lo-inch triplet, in which a
double concave lens has a central position and is used in making
the final adjustments, was ground and figured by Metcalf.
The definition given by this combination is unusually good over
a large field. The triplet is similar in construction to that
devised by H. Dennis Taylor, when a member of the English
firm of T. Cooke and Sons.
A fixed photographic telescope, having a lens of 12 inches
diameter, and of 135 feet focal length, with which W. H.
MISCELLANEOUS INSTRUMENTS
49
Pickering made systematic maps of the moon, was an interesting
experiment, though not of great general utility.
The 24-inch reflector mounted at Cambridge has been
of considerable value in obtaining material for special investiga-
tions.
Mention should be made of the development, by Gerrish,
of electrical methods for the control of large instruments. The
use of the electric motor synchronized by the pendulum of a
standard clock, instead of heavy weights, for driving the
instrument, as well as for securing slow motion in right ascen-
sion, has greatly facilitated the operation of heavy telescopes.
This method was introduced for the 24-inch reflector in 1907,
and was applied later to the 16- and 6o-inch telescopes.
OBSERVATORY INSTRUMENTS*
8-inch Bache Doublet
fS-inch Boyden Doublet
8-inch Draper Doublet
8-inch Refractor
f8-inch Polar Equatorial
fS-inch Doublets (Two)
f6H-inch Equatorial Refractor
fS-inch Transit Photometer (Two)
J4^-inch Transit Circle
t4-inch Meridian Photometer
f4-inch Comet-Seeker
4-inch Cooke Triplet
3 -inch Ross Patrol Telescopes (Three)
2%-inch Russian Transit
f 2-inch Meridian Photometer
* As of 1929; small portable telescopes and photographic cameras are not included in the
above list.
t Not now in active use.
6o-inch Reflector (Two Mirrors)
f 28-inch Draper Reflector
24-inch Bruce Doublet
24-inch Reflector
1 6-inch Metcalf Doublet
1 5 -inch Equatorial Refractor
i3-inch Boyden Refractor
12-inch Polar Equatorial
fi 2-inch (i35-foot) Refractor
i2-inch Metcalf Doublet
n-inch Draper Refractor
lo-inch Metcalf Triplet
t 83^-inch Meridian Circle
CHAPTER V
EXPEDITIONS AND FOREIGN STATIONS
REFERENCE has been made in Chapter I to astronomical
expeditions undertaken by members of Harvard University
during the first two centuries of its existence. The Harvard
Observatory since its foundation has carried out many scientific
expeditions several to observe total eclipses of the sun.
Total Eclipse of the Sun, 1851. After the establishment
of the Observatory, the first recorded attempt by a member of
the staff to observe a total eclipse of the sun was made by
George P. Bond in 1851. Taking advantage of a trip to Europe,
he made observations of the eclipse of July 28, at Lilla Eden,
Sweden. He was provided with a small telescope of about
two inches aperture and a power of 30 diameters, which was
loaned to him by Rlimker of the Hamburg Observatory. The
duration of totality was about four minutes. The conditions
for observation were perfect, and the scenic setting added to
the grandeur of the spectacle. Bond wrote a graphic account
of the event which exists only in typewritten form. His
scientific observations were published in the Astronomical
Journal for October, iSsi. 1
Bond was much impressed by the pure white beauty of the
corona and its visibility for an instant after the reappearance
of the sun. His comments on the prominences illustrate the
imperfect knowledge of that time regarding eclipse phenomena:
. . . they had rather the appearance of flames, not in sudden motion,
than of mountains, or of solid projections from the Sun, to which they
seemed to belong rather than to the Moon, if they are not optical
phenomena.
*A. J., 2, 49, 1851.
So
TOTAL ECLIPSE OF THE SUN, 1869 51
In the brief time at his command he recognized the real form
of one of the bridge-shaped prominences, which have been so
well shown in later years by photography.
Annular Eclipse of the Sun, 1854. Careful preparations
were made by the Observatory for the observation of the
annular eclipse of the sun on May 26, 1854. An arrangement
had been made with Dr. Bache, Superintendent of the United
States Coast Survey, by which George P. Bond, Charles W.
Tuttle, and Richard F. Bond, representing the Observatory,
were provided with telescopes and time-keepers. They planned
to observe the eclipse in New Hampshire from the summit of
Mount Washington, near the northern limit of the annular
phase. Unfortunately, after the laborious ascent of the moun-
tain, a cold rain prevented any observations. 2
Determinations of Longitude, 1855. Some reference
should be given to the various trips made in early days of the
Observatory for the determination of longitude. Before the use
of electrical methods, the determination of differences in
longitude was frequently made by observations of celestial
phenomena, and also by the transference of chronometers
from one station to the other, generally in care of ship's officers.
However, in order to obtain the best possible results for the
difference in position of Liverpool and Cambridge, Mr. Sydney
Coolidge, a volunteer assistant in the Observatory, took charge
of the transportation of the chronometers in 1855. He also
made the necessary transit observations both at Liverpool
and at Cambridge. Under his direction some 50 chronometers
were transported a distance of about 18,000 miles a large
undertaking in view of the slow ships of that day. 3
Total Eclipse of the Sun, 1869. The eclipse of 1869
occurred on August 7. Its path was from Alaska and Canada,
through Iowa, Illinois, Kentucky, and North Carolina. It
2 H. A., I, clxxviii, 1856.
8 Ibid., clxxxix.
52 EXPEDITIONS AND FOREIGN STATIONS
aroused wide interest and was observed by nearly all American
astronomers and by many from other countries. Congress
made a liberal appropriation for its observation. At the
request of Benjamin Peirce, Superintendent of the United
States Coast Survey, Winlock, then Director of the Harvard
Observatory, took charge of a party of observers at Shelbyville,
Kentucky. He made photographs of the corona and carried
on spectroscopic observations.
Other observers from the Observatory were Arthur Searle and
C. S. Peirce, who were assigned to adjacent locations in the belt
of totality. Peirce was stationed at Bardstown and Searle
at Falmouth. Edward C. Pickering, at that time Professor of
Physics at the Massachusetts Institute of Technology, made
spectroscopic and other observations at Mount Pleasant.
He also obtained a photograph of the corona with a portrait
lens. Survey parties occupied stations in Alaska, Iowa, and
Illinois, while representatives of other observatories and
independent observers were distributed along nearly the whole
path in the United States. The conditions of the sky were
generally favorable, and the scientific results obtained added
much to the knowledge of the nature of the sun.
Special attention was given to the form and nature of the
corona, about which little was then known, and to the spectrum
of the prominences. Photography was introduced on a scale
hitherto untried. A photograph made at Shelbyville with an
exposure of 40 seconds added to our knowledge of the form
and extent of the corona. Winlock observed in the spectrum
of the prominences during totality n bright lines of which 3
were visible before and after the total phase. He decided that
all such photographs should be made at the principal focus,
rather than with an enlarging lens, the more usual method at
that time. 4
Total Eclipse, 1870. The success of the observation of the
1869 eclipse induced many American astronomers to observe
4 H. A., 8, 56, 1876; Rep., U. S. Coast Survey, 116, 1869.
TOTAL ECLIPSE, 1870 53
that of the following year, on December 22, in Europe. Again
the Government of the United States, through the Office of the
Coast Survey, rendered important assistance. Benjamin
Peirce still retained his position as Superintendent of the Survey,
and was in general charge of American expeditions. Winlock,
aided by Henry Gannett, an assistant at the Harvard Observa-
tory, was placed in charge of the station at Jerez de la Frontera,
Spain. Charles S. Peirce occupied a station in Sicily. Asso-
ciated with Winlock in or near Jerez were a large number of
observers, some of whom later became famous. Among them
were Charles A. Young, Samuel P. Langley, and Edward C.
Pickering. The sky on the day of the eclipse was rather
cloudy, although at the time of totality the eclipse was only
partially obscured. A number of photographs were obtained
and many useful visual observations were made by members
of the expedition.
For use at this eclipse, Winlock devised a special attachment
for his spectroscope to ensure accuracy and speed in the deter-
mination of the positions of the lines observed. The arrange-
ment consisted of a point or cutting tool attached to that
part of the spectroscope which was moved to effect a pointing
on a given line. The record of position was impressed upon a
plate suitably placed. This apparatus appeared to work
successfully, but its importance became less with the introduc-
tion of photographic methods. Winlock had also constructed
a simple lens of long focus which was mounted in a fixed
position, the image of the sun being kept in position by a mov-
able mirror. This apparatus continued in use for a time at
Cambridge for taking daily photographs of the sun. The
method was not original with Winlock, but he seems to have
been the first to bring it into practical use.
Photographs made at the eclipses of 1869 and 1870 are
reproduced in the Harvard Annals. They were prepared in
general by drawings, photo-engraving processes at that time
not being well developed. 6
* H. A., 8, 56, 1876; Rep., U. S. Coast Survey, 134, 1870,
54 EXPEDITIONS AND FOREIGN STATIONS
Total Eclipse of the Sun, 1886. W. H. Pickering, while he
was a member of the faculty of the Massachusetts Institute of
Technology, formulated plans for the observation of the
eclipse which occurred on August 29, 1886. An account of this
expedition is given here, because Pickering soon after became
an assistant in the Observatory, and the Observatory provided
a part of the equipment and published the results in the Annals.
An appropriation of $500 was made by the Rumford Committee
of the American Academy of Arts and Sciences to aid the
expedition. This sum was to be applied to the purchase and
transportation of the necessary equipment, and, if anything
remained, to the cost of publication. Mr. Pickering paid his
own personal expenses and depended entirely on volunteer
assistants. The island of Grenada, in the West Indies, was
chosen as the site for the observations. Clouds covered the
sun on August 29 until within a few minutes of totality, when
conditions became favorable. Visual observations of Baily's
beads, shadow bands, and other eclipse phenomena were made
by members of the party and by local volunteer observers. The
principal instrument was a photo-heliograph of 38 feet focus,
intended for a study of the structure of the inner corona and
for a determination of its photographic intensity. Unfortu-
nately, no satisfactory photographs were obtained with this
instrument, although with others a few good plates were
obtained, showing the prominences and the form and intensity
of the corona. From these plates Pickering reached conclu-
sions regarding the structure of the corona, and the visual and
photographic intensity of the corona and of the sky. 6
Total Eclipse of the Sun, 1887. The Observatory took
part by proxy in expeditions to observe the eclipse of August
19, 1887. It was uncertain at that time whether the corona
was a fixed feature of the sun or whether it underwent rapid
changes. To determine this, two widely separated stations,
provided with similar apparatus, were needed. W. H. Picker-
6 H. A., 18, No. 5, 1890.
THE BOYDEN EXPEDITIONS, 1887 TO 1888 55
ing prepared the instruments and plates for the experiment.
Professor Charles A. Young at Rshev, Russia, and Professor
David Todd, at Shirakawa, Japan, undertook to have the proper
exposures made at these stations. Unfortunately, clouds
prevented successful photography. Had the weather permitted,
photographs would have been obtained at each station with a
lens of 10 inches diameter and of such a focal length as to
give an image of the sun i inch in diameter. In addition, in
Japan, photographs had been planned to give images of the sun
5 inches in diameter without enlargement. 7
The Boyden Expeditions, 1887 to 1888. A fund amount-
ing to about $238,000 was left by Uriah A. Boyden, of Boston,
for carrying on astronomical observations at such an altitude
as to avoid, so far as possible, the ill effects of the earth's
atmosphere. Early in 1887 the trustees of this fund transferred
it to the President and Fellows of Harvard College, for the use
of the Observatory.
A search for the site where Mr. Boyden's wishes might
best be carried out was at once undertaken, both by study
and correspondence and by personal investigation. Altogether,
a large number of more or less associated expeditions were
undertaken, during many years, in the fulfillment of this
obligation. The southern stations of the Observatory, first
in Peru and Chile and later in South Africa, were selected and
maintained in the spirit of Mr. Boyden's bequest.
Various appliances were devised to test the atmospheric
conditions at different sites. These appliances included photo-
graphic instruments showing the definition of star images and
trails and of trails of stellar spectra, at different localities and at
various altitudes. Meteorological observations, when not
already available, were undertaken by means of self-recording
instruments.
E. C. Pickering and W. H. Pickering visited different localities
and mountain summits in Colorado, in 1887. Records were
7 Ann. Rep., H. C. O., p. 6, 1887.
~
56 EXPEDITIONS AND FOREIGN STATIONS
continued after their departure by the aid of Professor F. H.
Loud, of Colorado College. Much valuable information was
furnished by General Greely, Chief of the United States Signal
Service.
Through the assistance of Mr. W. H. Cilley, of the
Oroya Railway, and Mr. V. H. MacCord, of the Southern
Railways of Peru, meteorological observations were carried
on during 1888 and 1889 to determine the desirability of a site in
some elevated locality in Peru. 8
Total Eclipse of the Sun, 1889. The total solar eclipse of
January i, 1889 was observed by several members of the
Observatory with a large equipment at Willows, California.
W. H. Pickering had charge of the expedition, assisted by King,
Black, and Bailey of the Observatory staff. Mrs. Bailey was
one of a large number of volunteer assistants. Russell T.
Crawford, later Professor of Practical Astronomy at the
University of California, was at that time a boy of thirteen
and a resident of Willows. He became an enthusiastic helper
in the work of the station.
The instrumental equipment for the observation of the
eclipse consisted of the i3-inch Boyden refractor, the 8-inch
Bache doublet, and several smaller instruments. The condi-
tion of the sky on the day of the event was nearly perfect.
Forty-seven photographs of different kinds were obtained,
and numerous visual observations were made. Valuable
meteorological observations were made by Professors Winslow
Upton and A. Lawrence Rotch. 9
A great crowd of onlookers gathered about the eclipse
station. As the corona flashed suddenly into view at the
instant of totality, a strange shout of applause, breaking a
deep and impressive silence, rose from the multitude.
The Mount Wilson Station, 1889 to 1890. After the
eclipse of the sun at Willows, W. H. Pickering proceeded to
southern California, which appeared to offer especial attrac-
*Ibid., p. 8, 1887; P- 7, 1888.
9 H. A., 29, No. i, 1893.
THE MOUNT WILSON STATION, 1889 TO 1890 57
tions for an observatory station. King and Bailey remained
to pack up the equipment, a part of which was destined for
some site in southern California and the remainder for Peru.
Mr. Pickering consulted with several persons in Los Angeles
and vicinity, and on January 23, 1889, accompanied by Alvan G.
Clark and a number of volunteers from Los Angeles, passed a
night on Mount Wilson. As a result of the information
obtained, it was decided to establish a provisional station
on the summit. After making some arrangements for this
purpose, Pickering returned to Cambridge.
King, assisted by Black, was chosen to take charge of the
installation and maintenance of the Mount Wilson Station.
The instrument selected was the Boyden i3-inch refractor
which had been successfully employed by King at the Willows
eclipse, and which was now forwarded to Mount Wilson, where
a suitable building was constructed for its protection. A
shelter was also provided for the two observers. No good
road to the summit existed at that time, and considerable
difficulty was experienced in conveying the heavier parts
of the instrument to the station. King and Black carried
on observations in this isolated location from May to November,
1889, when King returned to Cambridge. The photographic
work was continued into 1890 by Black, who then returned
the instrument to Cambridge for transshipment to the Peruvian
Station at Arequipa. The work carried out on Mount Wilson
was chiefly photographic. Many successful plates were
obtained of the moon, of planets, star dusters, double stars,
and nebulae.
Although the advantages of the climate of Mount Wilson
proved to be less satisfactory than had been anticipated, they
were, nevertheless, considered sufficient to justify the purchase
of a site and the foundation of a permanent station. For
various reasons, however, the attempt to obtain a secure title
was unsuccessful at the time, and later the establishment of
the station in the southern hemisphere made one on Mount
Wilson of less importance; hence the idea was abandoned.
58 EXPEDITIONS AND FOREIGN STATIONS
Many years afterward, Edward C. Pickering, while on a
visit to the mountain, made arrangements by which a memorial
tablet was placed on the site of the Harvard pioneer station.
It is near the present buildings of the Mount Wilson Observa-
tory of the Carnegie Institution.
First Peruvian Expedition, 1889. A recognition of the
need for astronomical observatories or stations in the southern
hemisphere was neither new nor peculiar to the Harvard
Observatory. Astronomers everywhere appreciated the neces-
sity of securing increased observations of southern stars. As
soon as Pickering began the Harvard Photometry at Cambridge
he was impressed with the desirability of extending the observa-
tions to the southern sky, and researches in stellar photography
only emphasized the necessity for a Harvard southern station.
The reception of the Boyden Fund made the establishment
of such a station feasible.
At first, two stations were under consideration, one in the
northern hemisphere so chosen as to fulfil the terms of the
Boyden bequest, the other in the southern hemisphere. There
appeared to be no good reason, however, why both considera-
tions, a lofty site providing the best attainable atmospheric
conditions, and a location somewhere south of the equator,
might not be combined in a single station. For such a station
the high plateaux and mountains of the west coast of South
America seemed to offer many attractions, and correspondence
was opened with various gentlemen in Peru. As a result
of these investigations, a preliminary expedition was sent
to Peru at the beginning of 1889, under the direction of S. I.
Bailey, at the same time that another expedition, described
above, was sent to test the climate of Mount Wilson, California.
On February 2, 1889, Mr - an d Mrs. Bailey and their son
Irving left San Francisco for Callao, Peru, on the San Josi, a
ship of the Pacific Mail Company. At Panama they were
joined by M. H. Bailey, who had with him additional apparatus
brought directly from the Cambridge Observatory by way of
H
h
<
h
03
PLATE VIII. (Above) MONT BLANC STATION, PERU. (Below) THE AREQUIPA
STATION, WITH EL MISTI IN THE BACKGROUND.
FIRST PERUVIAN EXPEDITION, 1889 59
New York. The chief instruments of the expedition were the
4-inch meridian photometer, which was to be used for the
extension of the Harvard Photometry, and the 8-inch
Bache doublet which had long been in use at Cambridge for
making stellar charts and spectrum plates.
As a result of somewhat extended investigations along
the Oroya railway, which runs from Callao through Lima to
the lofty interior of Peru, a preliminary station was chosen
near Chosica, a town lying in the valley of the river Rimac.
The valley itself at Chosica, shut in by lofty elevations, did not
give the desired horizon, especially to the north and south. A
summit was therefore selected, 8 miles by mule trail from the
village. This isolated site was occupied on May 8, 1889.
Portable buildings of rather light construction had been sent
from the United States. They served their purpose fairly
well in the mild climate of central Peru, even at the altitude
of 6500 feet. This hitherto unnamed summit was called
" Mount Harvard." The members of the mountain camp were
Mr. and Mrs. S. I. Bailey and son, Mr. M. H. Bailey, Seftor
Elias Vieyra, a Peruvian assistant, and two resident servants.
A muleteer made a daily trip from the valley to the station,
carrying food and water. Although 8 miles by trail from
the nearest neighbors, the station was often visited by Peruvians
and tourists, yet was never molested. It commanded a
wonderful view of Lima and Callao, the Pacific Ocean 30
miles away to the west, the great Andes on the east, and endless
mountain ridges and deep gorges on the north and south.
The sky at Mount Harvard became cloudy at the close
of the southern winter, and a further study of the west coast
was undertaken. Visits were made to Arequipa and vicinity,
to the region about Lake Titicaca, and to the deserts of Chile,
as far south as Valparaiso and Santiago. Two months were
passed at Pampa Central, a nitrate center on the Desert of
Atacama, in making observations for the Southern Harvard
Photometry. The sky on the desert was found to be very
dear, but living conditions would be both difficult and expen-
60 EXPEDITIONS AND FOREIGN STATIONS
sive for an astronomical station unless it were associated with
one of the large but uncertain nitrate or mining establishments.
As a result of all the investigations, Arequipa was recom-
mended for a permanent station, and this choice was approved
by the Director of the Observatory. On October 15, 1890,
Mount Harvard was abandoned with regret, and the instru-
mental equipment was removed to Arequipa, where the sky
remained favorable until about the middle of December. Late
December, January, February, and March proved to be very
cloudy, but the sky in April was exceptionally clear. During
the cloudy season, under the efficient guidance of Senor Juan
L. de Romana, of Arequipa, the various desirable sites in the
vicinity were carefully examined. The clear sky of April
permitted the completion of the observations for the Southern
Harvard Photometry, and, after assisting in the installation
of the new Arequipa Station, the Baileys returned to Cambridge
in May, 1891. 10
Second Peruvian Expedition, 1891; the Arequipa
Station. On January 17, 1891, Professor W. H. Pickering
arrived at Arequipa, accompanied by his family and by Messrs.
A. E. Douglass and George Vickers, assistants. They carried
with them the main equipment for the station, consisting of the
i3-inch Boyden telescope and various smaller instruments. To
these was added the apparatus used on Mount Harvard, with
the exception of the meridian photometer, which was returned
to Cambridge. Mr. Pickering selected a site for the station
which had been highly recommended by Senor Romana. It was
situated two miles northwest of Arequipa at an elevation of over
8000 feet above sea level, and 500 feet above the city. A
suitable residence, a laboratory, and buildings for the various
instruments were constructed within a few months.
The Arequipa Station of the Observatory remained in charge
of Mr. Pickering during the following two years. From 1893
until 1905, and in 1922 and 1923, it was in charge of S. L
w H. A., 34 Chap, i, 1895.
MINOR PERUVIAN EXPEDITIONS 6 1
Bailey for most of the time. In other years it has been, for a
longer or shorter period, in charge of H. C. Bailey, R. H. Frost,
Leon Campbell, Frank E. Hinkley, L. C. Blanchard, J. E.
Muiiiz, and John S. Paraskevopoulos. The other members
of the staff are listed in Chapter XX.
The station at Arequipa was maintained in active service
until 1927, a period of 36 years. A sufficient account of the
work done there is given in later chapters. In general the
observations were planned by the director in Cambridge, and
consisted in the extension to southern stars of the various
researches begun at Cambridge. At first many visual observa-
tions were made, such as those of the Southern Harvard
Photometry and its extensions, and the lunar and planetary
observations of W. H. Pickering and Douglass. Later the work
became more and more photographic. A few independent
investigations were made, such as the planetary work of W. H.
Pickering and the discovery of cluster variables by Bailey.
Minor Peruvian Expeditions. Various secondary expe-
ditions were undertaken by different members of the Arequipa
staff during the life of the station. In 1891, W. H. Pickering,
Douglass, and Vickers visited Bolivia and did some topo-
graphical work involving the measurement of several mountain
elevations, both in Peru and in Bolivia.
Under W. H. Pickering's direction, several visits were made
to the flank of the mountain range Chachani, 20 miles north
of Arequipa. A meteorological shelter was placed at an
altitude of 16,500 feet, and an unsuccessful attempt was made
to reach the summit, about 20,000 feet in elevation. While
returning to the United States, he obtained successful observa-
tions of the total eclipse of the sun at Mina Avis, near Vallenar,
Chile, on April 16, 1893. He was accompanied by Professors
A. Lawrence Rotch and A. E. Douglass. 11
In 1893, as a result of several exploratory trips made by
S. I. Bailey and other members of the staff, a meteorological
" Astr. and Ap., 12, 461, 1893.
62 EXPEDITIONS AND FOREIGN STATIONS
station was installed on the summit of El Misti, a nearly
extinct volcanic cone 19,200 feet high, about n miles northeast
of Arequipa. There was at that time a desire among mete-
orologists to obtain observations at the greatest possible
elevations. The Misti summit station was maintained for
about eight years, although not continuously. Visits to the
summit proved impracticable during the summer months
when the mountain was deeply covered with snow. Self-
recording instruments were employed which ran for 10 days
without rewinding, and eye observations were made when an
observer was present. The Misti Observatory appears to
have been the loftiest scientific station ever maintained. In
connection with the stations on the summit and flank of the
mountain, a series of similar meteorological stations were
maintained for many years, extending northward from the
Pacific Ocean at Mollendo across the western cordillera to
the high plateau, and thence beyond the eastern Andes to the
valley of the Urubamba, at Santa Ana, Peru. All of these
stations were occasionally inspected by a member of the
Arequipa staff. The observations were made, in general, by
resident natives, in some cases gratuitously. 12
Professor Winslow Upton, of Brown University, and formerly
an assistant in the Observatory, passed ten months at the
Arequipa Station, during the years 1896 and 1897, for the
purpose of determining its precise geographical position. His
outfit consisted of two portable transit instruments, two
mean time chronometers, a sidereal clock, a sextant, an engi-
neer's transit, and several minor instruments. Assistance
was given by members of the Arequipa Station. Telegraphic
signals were exchanged between the station and Arica, Chile,
whose position was accurately known. All of the observations
at Arica were made by Professor Upton. The resulting longi-
tude of the transit instrument of the Arequipa Station was
4* 46 n*.73 west f Greenwich. The latitude was found to be
16 22' 28".o, and the altitude above mean sea level, 8043 feet.
H. A., 39, 1906; 49, i, 1907.
s
CO
w
H
I
h
o
u
(/)
u
j
w
w
H
SECOND JAMAICAN EXPEDITION, 1900 TO 1901 63
Mr. Upton also determined the relative positions of various
points in the vicinity of Arequipa. 13 *
First Jamaican Expedition, 1899. An expedition was
undertaken by W. EL Pickering to test the "seeing," and to
determine whether the island of Jamaica offered favorable
atmospheric conditions for the use of a large telescope. Tests
were made with a five-inch telescope at various localities, a
standard scale of seeing devised by W. H. Pickering and
Douglass being used. The results of such tests made during
July and August, 1899, were compared with the results of
similar tests made at Cambridge both before and after the trip.
The atmospheric conditions in Jamaica were found to be favor-
able in several localities, especially at Mandeville. 14
Total Eclipse of the Sun, 1900. An expedition under-
taken largely at the expense of the Observatory, was sent to
Washington, Georgia, on May 28, under the direction of W.
H. Pickering. The special object of the expedition was a
search for a possible intra-mercurial planet. Unfortunately
no satisfactory results were obtained. Good photographs of
the inner corona and prominences, however, were made at
Wadesboro by an expedition sent out by the Secretary of the
Smithsonian Institution, which used a new telescope of 135 feet
focus, loaned by the Harvard Observatory. 15
Second Jamaican Expedition, 1900 to 1901. A second
expedition to Jamaica was undertaken by W. H. Pickering,
assisted by E. R. Cram, to test the value of a telescope having
a lens of moderate aperture and great focal length. For this
purpose a lens had been made with a diameter of 1 2 inches and
a focal length of 135 feet. The instrument had already been
found useful at the total eclipse of 1900, as stated above.
It was sent to Jamaica later in the same year. At Mandeville,
the lens and the photographic tailpiece were placed in different
18 H. A., 48, No. 9, 1903.
14 H. A., 51, Chap. 2, 1903.
11 Ann. Rep., H. C. O., p. 16, 1900; Pop. Astr., 8, 225, 1900.
64 EXPEDITIONS AND FOREIGN STATIONS
shelters connected by a covered way. The light was thrown
on the stationary lens by a movable mirror having a diameter
of 1 8 inches. The observations, of which an account is given
in Chapter VII, were chiefly of the moon, and were made from
January to August, 1901. Some investigation was also made of
the suitability of the instrument for stellar photography. In
his Annual Report for 1901, the director, E. C. Pickering,
states: "The long-focus telescope is, therefore, again in Cam-
bridge. Apparently an instrument of this form is not well
adapted to the study of the stars, unless it can have a much
larger aperture." 16
First South African Expedition, 1908 to 1909. After
nearly 20 years' trial of the climate of Arequipa, it seemed
important to investigate whether better conditions were
to be found elsewhere for the southern station of the Observ-
atory. Arequipa is in many respects an almost ideal site.
For six months of the year, from May to October, the conditions
leave little to be desired. Not only is the sky sufficiently clear,
but the steadiness of the air, the moderate diurnal range of
temperature, and the absence of dew are most satisfactory.
Occasionally such conditions prevail throughout the greater
part of the year, leaving a short and broken cloudy season.
Ordinarily, however, the cloudy season is long and unbroken,
interfering seriously with the work of the station.
The elevated plateau of South Africa had been highly
commended to Pickering by Sir David Gill, Sir William Morris,
and others familiar with its characteristics. Accordingly
an expedition in charge of Bailey was sent to investigate the
country. A visual telescope of 10 inches aperture, one of 5
inches aperture for testing the seeing, a photographic camera,
and a varied equipment for meteorological observations, were
provided.
Brief preliminary visits were made to various localities
in Cape Colony, the Orange River Colony*, the Transvaal,
"H. A., 51, 1903.
FIRST SOUTH AFRICAN EXPEDITION, 1908 TO 1909 65
and Rhodesia. Hanover, on the Upper Karoo, most highly
recommended by Sir William Morris and others, was selected
as the principal station for more detailed investigation. The
lo-inch telescope was set up and provided with a suitable
shelter, and astronomical observations were carried on when-
ever possible. Systematic meteorological observations were
also made at Bloemfontein, largely through the volunteer
assistance of Mr. James Lyle, and at Worcester by the aid of
Mr. Izak Meiring. Mr. L. S. Schultz, a resident of Hanover,
was engaged as an assistant to aid in the observations in that
village. The meteorological observations at those three
stations were continued throughout the year 1909. Bailey
returned to Cambridge in December of that year, but the
Hanover station was left in care of Schultz, who carried on
observations for several months in 1910. Toward the end the
observations were irregular and unsatisfactory, and the station
was closed.
The results of the expedition can be summarized briefly.
The high plateau of South Africa offers many inducements
for the establishment of a permanent astronomical station.
The conditions are good over a wide area. The amount of
clear sky and especially its distribution throughout the year,
are much more favorable than at Arequipa. On the other
hand, the steadiness of the atmosphere, though good, is no
better than that of Arequipa, and the diurnal range of tem-
perature and the precipitation of dew are greater. Dust
storms and violent thunderstorms are also common in South
Africa. From a purely scientific standpoint, Hanover, an
attractive but isolated village, offers very strong advantages.
The conditions at or near Bloemfontein are almost equally
good, however, and the social advantages for a scientific staff,
incomparably superior. The conditions at Worcester are
good, with an almost uniform distribution of the cloudiness
throughout the year, but the sky is distinctly less transparent
than on the plateau. Johannesburg has the social and other
advantages of a large city, and also favorable climatic con-
66 EXPEDITIONS AND FOREIGN STATIONS
ditions. Regarded from all considerations, Bloemfontein
appeared especially favorable, and is probably not surpassed
by any other locality in South Africa for an astronomical
observatory. No action was taken at the time, however,
since the financial condition of the Observatory did not then
permit the large expense involved in transferring the station
from Arequipa to South Africa. 17
The Station at Mandeville, Jamaica, 1912. W. H.
Pickering became permanently established at Mandeville in
1912. Little photographic work has since been done at the
station. Mr. Pickering has devoted his time chiefly to visual
observations of the moon and planets, using the n-inch Draper
refractor. The station was a part of the Harvard Observatory
and was maintained by it until Pickering's retirement from the
staff in 1924. Since that time he has maintained the station
as a private observatory. The n-inch telescope is now in
Cambridge, where in recent years it has contributed significantly
to the new developments in the field of spectrophotometry.
Chuquicamata and San Jose Stations, 1923 to 1926.
Dr. John S. Paraskevopoulos was placed in charge of the
Arequipa Station late in 1923. By request of the director,
Dr. Shapley, he undertook, in December, 1923, an expedition to
Chuquicamata, a mining town in the desert region of north-
eastern Chile. The region had long been known to have a
favorable sky. At Arequipa, the conditions are satisfactory
for six or eight months, but from December to March, the
southern summer, the sky is usually almost continuously
cloudy at night. As far back as 1890, it had been shown by
Bailey, as a result of two months passed at Pampa Central,
a nitrate town in the desert southwest of Chuquicamata, that
the region gave good conditions during the months most cloudy
at Arequipa. In more recent years, observations made by
L. B. Aldrich at a station near Chuquicamata, maintained
17 Ann. Rep., H. C. O., 1908, 1909, 1910; ScL Mon., ai, 225, 1925.
TOTAL ECLIPSE OF THE SUN, 1925 67
by the Smithsonian Institution for the study of the sun,
showed that excellent conditions prevailed there throughout
the year.
Paraskevopoulos took with him to Chuquicamata in Decem-
ber, 1923, two photographic telescopes of moderate size,
and carried on work during the months most cloudy at Arequipa.
The results were very satisfactory. A second expedition to
the same site in the cloudy season of 1925 to 1926 gave similar
results.
During the intervening cloudy season of 1924 to 1925,
a study was made by Paraskevopoulos of the conditions at
San Jose, a railway station on the desert between Arequipa
and the Pacific Ocean. A station in this vicinity, since it
is near to Arequipa and accessible by rail, would have been
much more convenient than one in Chile, had it proved favor-
able. The conditions proved to be very poor, however, and
the observations appeared to demonstrate that no advantage
would be gained by moving to San Jos6, or to any site on the
Desert of Islay.
The continuance of the station at Arequipa alone involved
the loss each year of about four consecutive months. The
selection of Chuquicamata alone as the site of the southern
station would, indeed, provide a very clear sky, but an extremely
inhospitable desert site. To occupy permanently two widely
separated stations would involve many inconveniences. It
would cause much extra labor, greater expense, a larger equip-
ment, and considerable loss of time. Under these circum-
stances, Dr. Shapley decided to remove the Arequipa Station
to South Africa.
Total Eclipse of the Sun, 1925. Observations of the
eclipse of January 24, 1925, were undertaken at several widely
separated stations. The chief object was a determination of
the total light of the corona by a plan devised by King. Shapley
was at Buffalo, New York, where clouds interfered. Miss
Cannon was stationed at Poughkeepsie, New York, Campbell
68 EXPEDITIONS AND FOREIGN STATIONS
at New London, Connecticut, and King and Miss Payne on
Nantucket Island, where Miss Harwood, Director of the
Maria Mitchell Observatory, took part in the observations.
Dr. W. J. Fisher observed the eclipse near North Falmouth,
Massachusetts, at the northern edge of the path of totality.
Dr. W. J. Luyten made observations near New York City,
from an airplane, which was prepared, if necessary, to rise
above any obscuring clouds. Nearly all the members of the
Cambridge Observatory visited the path of totality. It is
doubtful whether a total eclipse of the sun was ever seen before
by so many individuals. The conditions were favorable in
most localities, and the interesting event was observed by
several million people. Many special trains were run to
favorable localities from Boston and other large cities.
From the numerous photographs obtained of the corona,
King found among other things that the integrated brightness
of the corona within a circle 3 in diameter, in stellar magni-
tudes, is 10.96 photographic, and 11.61 photovisual,
with a color index of +0.65, corresponding in spectrum to a
star of Class Go. 18
Additional results were obtained from photographs made
at the Maria Mitchell Observatory by Miss Harwood. The
integrated photographic magnitude of the earthlight on the
full disc of the moon was found to be 3-2O. 19
The New Southern Station at Mazelspoort, near Bloem-
fontein, 1927. Generous gifts from the International Educa-
tion Board and from Harvard University provided funds in
1926 for the transfer of the Boyden Station to a more favorable
locality. Dr. Shapley finally decided to remove the station
from Arequipa, Peru, to a site near Bloemfontein, O.F.S.,
South Africa.
A beginning was made in dismounting the various instru-
ments at Arequipa in November, 1926, and in February,
18 H. C. 286, 1925; Pop. Astr., 33, 289, 1925.
H. C. 312, 1927; Pop. Astr., 33, 344, 1925-
THE NEW SOUTHERN STATION AT MAZELSPOORT 69
1927, they were forwarded to Bloemfontein. The Bruce
telescope, however, was sent to Pittsburgh, Pennsylvania,
where a new mounting was to be constructed by Mr. J. W.
Fecker, before its transshipment to South Africa. Dr. and
Mrs. Paraskevopoulos reached Bloemfontein in July, 1927.
After some investigations into the desirability of various
localities near that city, a permanent site was chosen at Mazel-
spoort, about 14 miles northeast of Bloemfontein. The
position of the new Boy den Station is approximately i h 45"* 37*
east longitude and 29.2 south latitude. The altitude is about
4500 feet. Assistance in preliminary explorations for a site
was rendered by Professor R. A. Rossiter, Superintendent of the
Bloemfontein Station of Detroit Observatory of the University
of Michigan. The City of Bloemfontein made generous
financial contributions to the establishment of the Harvard
Station, by the building of roads, by the laying of water, power,
and telephone lines, by expert engineering service, and in other
ways. The station is on the summit of a " kopje," or hill,
near the water and electric plants of the City of Bloemfontein.
By the end of 1927, considerable progress had been made in the
building of the new station.
CHAPTER VI
PUBLICATION OF SCIENTIFIC RESULTS
The Harvard Annals. The founders of the Observatory
early recognized that the success of a scientific institution
must be judged mainly by its published results. " Statutes"
for the guidance of general policies, and " Regulations " in
regard to the publication of observations, prepared by Presi-
dent Jared Sparks, were passed in December, 1849. Among
the regulations it is ordered that:
The publication shall be entitled, Annals of the Astronomical Observa-
tory of Harvard College; the volumes, or parts of volumes, shall be uni-
form in size, quality of the paper, and style of execution, and the title-page
of each volume shall bear an inscription indicating from what source the
means of printing it were derived. 1
The Annals thus became the official publication for the
more extensive investigations of the Observatory. Begun
under the Bonds, they have been carried forward by Winlock,
Pickering, and Shapley, and their associates, until at the
present time they consist of nearly 100 quarto volumes.
The nature of the Annals has changed considerably; the
contents of early volumes are more general than those of recent
times. Volume I contains the early Annual Reports of the
Director and of the Visiting Committee, important correspond-
ence regarding policies and instruments, and other matters not
purely astronomical. Also, during the early years, and
especially during Pickering's administration, meteorology
received much attention. This was in harmony, nevertheless,
with the Statutes of the Observatory, which state:
The objects of the Observatory are, to furnish accurate and systematic
observations of the heavenly bodies for the advancement of Astronomical
1 H. A., x, Ixii, 1856.
70
THE HARVARD CIRCULARS 71
Science, to cooperate in Geodetic and Nautical Surveys, in Meteorological
and Magnetical Investigations, to contribute to the improvement of
Tables useful in Navigation, and, in general, to promote the progress of
knowledge in Astronomy and the kindred Sciences. 2
William C. Bond's interests and observations related chiefly
to geodesy and navigation; and magnetic and meteorological
observations occupied the attention of the volunteer assistants
at the old Dana House Observatory. Under Pickering's
administration an intimate relation existed between the
Astronomical Observatory and the Blue Hill Meteorological
Observatory, which later became a separate department
of the University, though its observations for many years
had been published in the Annals. 3 Certain observations
of the New England Meteorological Society and the New
England Weather Service also appeared in the Annals. 4 In
connection with the study of climatic conditions at the southern
stations of the Observatory, many meteorological observations
were made which have been published in the Annals under the
heading " Peruvian Meteorology." 5
At the present time, the work of the Observatory is con-
fined chiefly to astronomical investigations, and the Annals
contain only the results, usually in catalogue or tabular form,
of the larger researches, such as the great catalogues of the
Harvard Photometry and its extensions, and especially the
Henry Draper Catalogues of stellar spectra. 6
The Harvard Circulars. For the prompt announcement
of the results of its work, the Observatory began in 1895 the
publication of Circulars. As planned by Pickering, these
Circulars were to be somewhat comprehensive in their scope,
in order to include the results of recent observations, new
plans of work, gifts, and bequests, and, indeed, any subject
9 Ibid., lix.
8 H. A., 20 ; 30 ; 40 ; 42 ; 43 ; 58 ; 68 ; 73 ; 83 ; 86, Parts i, 2, 4; 87, Part i.
4 H. A., 21 ; 31 ; 41, Nos. 1-4.
'H. A., 39 J4Q; 86, Part 3.
H. A., 14; 23; 24; 26; 27; 28; 34; 44; 45; 46; 50; 54; 91-100.
72 PUBLICATION OF SCIENTIFIC RESULTS
of astronomical interest. They generally contained a few
quarto pages. At the present time, with the changed character
of the Bulletins, the Circulars are confined more strictly
to purely astronomical subjects, and contain such single
investigations as in earlier years would have formed Numbers
in volumes of the Annals devoted to miscellaneous researches.
The number of Circulars issued up to the end of the year 1927
was 319.
The Harvard Bulletins. The Harvard Observatory has
always made some effort to announce important astronomical
discoveries to the public as well as to other observatories. In
his Annual Report for 1883, Pickering described an important
extension of the system of announcing astronomical discov-
eries by telegraph and cable, a service that had been in use for a
number of years. An association of 50 European observatories
was formed with headquarters at Kiel, for the purpose of
giving prompt information about astronomical discoveries in
different countries. An American service of this nature, which
had previously been rendered by the Smithsonian Institution,
was transferred to the Harvard Observatory as the American
counterpart of the European bureau.
For a long time this service was telegraphic only, but in
1898 the Harvard Bulletins were introduced in order to supple-
ment the telegraphic service by promptly mailed announce-
ments of important discoveries. For many years the Bulletins
were devoted chiefly to cometary announcements. At first
they were neostyled from hand-written copies, but beginning
with No. 501, issued on October i, 1912, the Bulletins have been
printed. Later the scope of the Bulletins was extended to
include notes on novae, variable stars, and other objects.
Under Dr. Shapley's direction the nature of the Bulletins
has been completely changed. They have taken on in large
measure the character of the Circulars, but each contains
several communications instead of only one. Since October,
1926, they have generally been issued regularly on the first day
HARVARD REPRINTS 73
of each month, and have been much enlarged, containing
announcements on many subjects under investigation in the
Observatory. The number of Bulletins issued up to the close
of the year 1927 was 853.
Harvard Announcement Cards. The change in the scope
and periodicity of the Bulletins left a need for prompt announce-
ments, and the Harvard Announcement Cards were begun on
March 12, 1926. This series of cards gives immediate distribu-
tion to astronomical announcements received by telegram.
They are similar in purpose to the early Bulletins. They can
be sent out much more promptly than the present Monthly
Bulletins, and they relieve them from including telegraphic
announcements regarding comets, novae, asteroids, and similar
matters.
Harvard Reprints. In 1923, in order to bring together
into convenient and accessible form various astronomical
communications made by members of the Observatory to
different scientific journals, a series of reprints was inaugurated.
By the end of 1927 the number of such reprints was 42. Prior
to the beginning of this series, a large number of astronomical
papers had been published by members of the staff in various
journals, and can be found only by laborious searching of the
indices. The Bonds, in addition to their contributions to the
Annals, published nearly 200 papers in outside journals, and
during the long directorship of Pickering the number of such
contributions was also very large; they appeared in the publica-
tions of the American Academy of Arts and Sciences, in the
Monthly Notices of the Royal Astronomical Society, the
Astronomische Nachrichten, the Astronomical Journal, and
elsewhere. Recently, such papers have appeared chiefly in the
Proceedings of the National Academy of Sciences, Popular
Astronomy, and the Proceedings of the American Academy of
Arts and Sciences. Many of the earlier communications were
important scientific treatises; others were more in the nature of
announcements of astronomical discoveries. Even a proper
74 PUBLICATION OF SCIENTIFIC RESULTS
index of them all would fill a small volume, and although its
inclusion here would be desirable, it is evidently impossible.
The Annual Reports. The Report of the Director was
first issued in 1846, and the Annual Reports have since been
continued without interruption; all have been published except
those for the years 1856 to 1858, and 1874 to 1876. They
give a synopsis of the work and needs of the institution, and
provide a brief history of its activities. The earliest numbers
were published in the first volume of the Annals. Later
numbers were included in the Annual Reports of the President of
the University, and were also issued as separate reprints.
Additional notes on the activities of the Observatory can be
found in the Annual Reports of the Visiting Committee, which
were also begun in 1846 and were continued with few breaks for
many years. The early reports were printed in the first volume
of the Harvard Annals. When made in writing, they have
also been published by the University in connection with the
reports of the Visiting Committees appointed by the Board of
Overseers for the various departments of the University.
Harvard Monographs. A series of Monographs was begun
in 1925 with the publication in book form of "Stellar Atmos-
pheres," by Miss Payne. The Monographs were designed to
have a larger scope and rather a more readable form than the
more restricted Circulars and Bulletins. It is planned that
other volumes of a monographic nature will be issued in the
same form. The second of the series is Dr. Shapley's mono-
graph on star clusters a summary of his own contribution
to the subject and of other relevant investigations, and con-
taining a large amount of material not published before.
The third is a spectroscopic study, by Miss Payne, of the high
luminosity stars supplanting many sections of her earlier
book and carrying further the problems outlined there. The
present volume is the fourth of the series. Volumes dealing
with meteoric problems, by Dr. Fisher, and with long period
MISCELLANEOUS 75
variables, by Dr. Shapley, Mr. Campbell, and Miss Payne,
are in preparation or under consideration.
Miscellaneous. In addition to its printed publications,
the Observatory has issued astronomical photographs and
lantern slides, not only for the use of astronomical societies,
but for the instruction of students and the public. An exhibi-
tion of illuminated transparencies of celestial objects has long
been a permanent feature of the Observatory, and similar glass
positives have been sent to other places to form a part of
such exhibitions. Most students and visitors can gain much
more information from an inspection of such photographs
than from observations with the telescope.
Funds for publication were lacking during the early years
of the Observatory. Such funds have since been provided,
but not in such amount as to avoid the necessity for great
care and economy. At all times the Observatory has depended
in part on special gifts to prevent serious delay in the publica-
tion of the results of its work.
PART II
THE SCIENTIFIC PROBLEMS
CHAPTER VII
THE SOLAR SYSTEM
The Brightness of the Sun. Although systematic and
extended solar research has never been a part of the Observ-
atory program, interesting pioneer work has been done on
sunspots, on the solar spectrum, and especially on the photom-
etry of the sun. One of the earliest contributions from the
Observatory was a series of sunspot drawings for the years
1847 to 1849, by William C. Bond. These, with brief notes,
were published after much delay in 112 plates. 1 The series,
of course, does not compare favorably with later photographic
work, but since they antedate solar photography the plates
are of considerable value. A large number of fine drawings
of solar spots and prominences were also made by Trouvelot
in the years 1872 to 1874, specimens of which were reproduced
in the Annals. 2
Many determinations of the brightness of the sun, expressed
in stellar magnitudes, have been made by astronomers, the
light of the sun being compared with that of Sirius and other
stars. As early as 1860 George P. Bond determined the relative
light of the sun and moon, and compared sunlight with the light
of various celestial objects. He found that the sun gives
us nearly 6,000,000,000 times as much light as Sirius, over
3,000,000,000 times as much light as Jupiter at opposition,
and 622,600,000 times the light of Venus at maximum. Such
difficult comparisons of sunlight and starlight are never made
by the casual observer of the heavens he is more likely to
compare the brightness of the sun and moon; Bond found that
* H. A., 7, 1871.
8 H. A., 8, Part 2, 1876.
79
8o THE SOLAR SYSTEM
the sun gives us 471,000 times as much light as the mean full
moon. 20
One of the objects of the second Jamaican expedition,
undertaken in 1900, was to obtain, if possible, satisfactory
determinations of the brightness of the sun and moon. Exten-
sive observations were made, and the sun's light was compared
with that of Sirius, Capella, Arcturus, and Vega. As a mean
of the results of these comparisons, William H. Pickering found
26.83 f r the visual magnitude of the sun. 3 In other words,
the sun gives about 10*0 times as much light as a first-magnitude
star.
Among the more important contributions from the Harvard
Observatory to solar astronomy is the determination of the
photographic and visual magnitudes of the sun by Edward
S. King an investigation extending from the year 1903 to
1910, and culminating in the values 25.83 and 26.81,
respectively. 4 Although carried out by different and independ-
ent methods, these results by King agree closely with those
obtained by the Pickerings.
To test the constancy of the sun's magnitude, Leon Campbell
undertook in 1917 a long series of visual photometric observa-
tions of the planet Uranus, following a suggestion of Edward C.
Pickering that any conspicuous variations in the total solar
radiation should be revealed by accurate photometry of Uranus,
whose light could be directly compared with that of neighboring
stars. Campbell found, not a variation in the sun's light, but
the variability of the light of Uranus itself. The observed
range was 0.15 magnitude, and the period of 0^.451 agrees
so well with the period of rotation as determined spectroscopi-
cally at the Lowell Observatory, that the fluctuation was
assumed to be due to the rotation of the planet, different por-
tions of whose surface are unequally bright. 6
2tt Mem. Amer. Acad., 8, 221, 287, 1861; M. N. R. A. S., 21, 197, 1861.
3 H. A., 61, Chap. 5, 1908.
4 H. A., 59, No. 10, 1912.
6 H. C. 200, 1917.
THE MOON'S BRIGHTNESS 8 1
Reflected sunlight has been studied not only by means of
the planets and the moon, but also through observations of the
zodiacal light and Gegenschein. Investigations on the appear-
ance and nature of the zodiacal light were made by Arthur
Searle for many years, beginning in 1877, but occasional
observations had been made at the Observatory since 1840.
The details of these observations, and a discussion of them on
the theory that the light is caused by sunlight reflected from
particles belonging to the solar system are given in Harvard
Annals 19, Part 2, 1893. Searle later published observations
of the Gegenschein made by various observers, especially at
Arequipa. 6 He also discussed certain luminous bands which
in his opinion affect the appearance of the zodiacal light. 7
The Solar Spectrum. With the development of photo-
graphic methods, Edward C. Pickering included some work
on the solar spectrum in the general study of spectral classifica-
tion, paying special attention to the varying intensity of the
atmospheric lines in the solar spectrum as affected by variations
in temperature, moisture, and other meteorological conditions. 8
He also did pioneer work on line intensity for the spectral
regions around the Fraunhofer line E, 9 and thus helped to pave
the way for the future investigations of solar and stellar
atmospheres.
Recently there has been a renewal of researches on line
intensity in the solar spectrum, using the searching methods
of spectrophotometric analysis recently developed at the
Observatory. The sun, therefore, while not assiduously
studied, is not absent from the Observatory's programs, and is
kept constantly in mind as one of the stars.
The Moon's Brightness. Work on the photometry of the
moon was begun early, and also on that of other members of
the solar system. George P. Bond, in 1860, presented to the
6 H. A., 33, No. 2, 1900.
*/ta*., No. 3-
8 H. A., 48, No. 8, 1903.
H. C. 72, 1903.
82 THE SOLAR SYSTEM
American Academy of Arts and Sciences two papers on this
subject. 10 Bond's experiments, based in part on photographs
made by Whipple with the large refractor, were pioneer efforts
in photographic photometry and led to interesting results.
They appeared to show that the moon absorbs about 10 parts
out of ii of the light that falls upon it; Jupiter, on the other
hand, appeared to reflect, or at least to shine with, more light
than falls upon it from the sun that is, to be slightly self-
luminous. This result for Jupiter has never been certainly
confirmed. Bond found full moonlight to be 7.38 times as
bright as half moonlight a difference of 2.17 magnitudes and
only 1/471,000 as bright as the sun.
This value for moonlight was corrected by W. H. Pickering's
observations made in Jamaica in 1900. He found the visual
magnitude of the moon to be 12.50. Assuming this value
and the corresponding magnitude of the sun, 26.83, the sun's
light is about 540,000 times that of the full moon. 11
As a part of his extended investigations into photographic
photometry on a uniform scale, Edward S. King made a
determination of the photographic magnitude of the moon at
different phases. Photographs of the moon, having various
exposures, were compared with standard squares formed by the
light of an Argand lamp. King's results were derived from a
study of nearly a hundred plates taken at all seasons and at
different temperatures, careful attention being given to the
effects of changes in temperature and humidity. A photo-
graphic magnitude of 11.20 was obtained for the light of the
full moon, and of 9.01 for the half moon, a result which
agrees well with the early determination of Bond. The
photometry of the sun and moon presents many difficulties and
is still a subject of investigation by Professor King. 12
The Surface of the Moon. In 1871, N. S. Shaler, Professor
of Palaeontology at Harvard University, having previously
10 Mem. Amer. Acad., 8, 221, 287, 1861; M. N. R. A. S., 21, 197, 1861.
" H. A , 61, Chap. 5, 1908.
H. A., 59, No. 3, 1912.
THE SURFACE OF THE MOON 83
had the moon under observation for several years, employed
the large refractor on 35 nights in a study of the surface of the
moon from the standpoint of a geologist. He came to the con-
clusion that all the contours of the lunar surface are the results
of volcanic action, and that the radiating bands are crevices
stained on their borders by escaping gases. 13 Similar views
have been held by many selenographers, but the origin of the
lunar markings is still in doubt.
During the years 1872 to 1874, the large refractor was used
by Trouvelot, who made many elaborate and beautiful drawings
of celestial objects, including details of the lunar surface. A
number of these were published in Harvard Annals, 8, Part 2,
1876. No more accurate representations of the surface of the
moon were ever made before the perfection of photographic
methods.
From his entrance into the Observatory in 1886 until the
present time (1927), William H. Pickering has given much
time to observations of the lunar surface. He early announced
his rejection of the general belief that the moon is an entirely
dead and waterless world, void of any atmosphere. His
own observations, supported by those of other observers,
indicated, in his opinion, considerable changes on the lunar
surface, especially in the craters Plato and Linne. He even
concluded that his observations pointed strongly to the exist-
ence of some form of lunar vegetation at the present time. He
asserted the existence of a lunar atmosphere, and was con-
vinced that his observations of Linne made during the total
eclipse of October 16, IQO2, 14 showed definite changes.
W. H. Pickering also prepared an atlas of the moon in 80
photographic plates. The visible surface of the moon was
divided into 16 parts, and each of these is represented on five
plates, one showing the region at lunar sunrise, one at sunset,
and other plates at intermediate phases. The changes in the
appearance of lunar features under varying illumination are
" H. A., 8, 50, 1876.
14 H. A., 32, 1894; H. C. 67, 1902.
84 THE SOLAR SYSTEM
thus strikingly shown. Pickering was of the opinion that
these photographs also show genuine physical changes in the
lunar features, especially in the crater Linn6; and he supple-
mented the photographs by elaborate drawings. The scale of
all the plates is 5 seconds of arc to the millimeter. One of the
most interesting features in connection with this research is the
instrument with which it was undertaken. The photographs
were made in the principal focus of a telescope having a lens
of 12 inches diameter and 135 feet focal length. At that time
it seemed uncertain whether such an instrument might not
surpass telescopes of more usual construction in certain lines of
photographic work. The moon appeared to offer the best test.
In definition the results did not compare favorably with the
best photographs of the day, and they are, of course, far sur-
passed by photographs made with the great instruments of
later date. The experiment, however, was well worth a trial. 15
Much additional work has been done on the moon by W. H.
Pickering. 16
Lunar Eclipses. The total lunar eclipse of January 28,
1888, was observed with three ends in view: observations of
occultations of stars, desired by Struve; a study of the varia-
tions of actinic brightness; and, especially, a search for a possible
lunar satellite. A theoretical determination of the probable
size of such a satellite, its distance, and possible magnitude,
was made by W. H. Pickering, but a search for it on several
good photographs that were secured led to negative results.
The conclusion reached was that no object so bright as the
tenth magnitude could have escaped detection, and that the
moon can have no satellite more than 200 meters in diameter. 17
Later attempts have been made to find a lunar satellite, but
without success.
Eclipses of the moon may yield other observations of value,
such as the occultations of faint stars, which may be used for
"H. A., 51,1903.
18 H. A., 53, No. 4, 1904; 61, Chap. 8, 1908.
17 H. A., 18, No. 4, 1890.
DETERMINATION OF THE MOON'S POSITION 85
determination of the dimensions and parallax of the moon,
study of the earth's shadow, as projected on the eclipsed
oon, may also contribute something toward a better knowledge
the earth's atmosphere.
An extended investigation of the lunar eclipses between
!6o and 1922 has been made by Dr. Willard J. Fisher, in the
>pe of finding evidence of a structure of the earth's shadow
^responding to the known dust layers of the atmosphere,
roof of such a relationship was not immediately obtainable,
it a thorough study was made of the relative brightness of the
lipses. Fisher found that the position of the moon's path
ith regard to the center of the shadow is significant; that the
Feet of volcanic dust is evident in the shadow on the moon;
id that the atmosphere of the earth's northern hemisphere is
ss transparent than that of the southern. 18 Dr. Fisher later
scussed many observations of the total eclipse of the moon of
ugust 14, 1924, which had a dark spot visible near the middle
the shadow. The conclusion previously reached was
jrified, that the atmosphere of the earth's northern hemisphere
less transparent than that of the southern hemisphere. 19
Determination of the Moon's Position. The first
,tempt to determine the position of the moon photographically
as made by George P. Bond in 1857. Various attempts were
ade later by European astronomers. In 1911 Edward C.
ickering, in consultation with Ernest W. Brown of Yale
niversity and Henry N. Russell of Princeton University,
idertook further researches to this end. The success of the
idertaking was largely due to Edward S. King, who perfected
ie apparatus and technique for obtaining suitable photographs,
he measuring of the plates and the discussion of the results
ere carried out by Professor Russell, or under his direction,
ussell concluded that " the photographic method, at the first
ial, gives results apparently somewhat superior in accuracy
18 Smithsonian Miscellaneous Collection, 76, No. 9, 1924.
H. C. 284, 1925-
86 THE SOLAR SYSTEM
to meridian observations of the highest class." Later measure-
ments confirm this estimate of accuracy. Russell states that
it is obvious from an inspection of the diagrams that the
precision of the photographic observations is on the average
at least fully comparable with that of the Greenwich meridian
circle and greater than the altazimuth observations. 20
The Observatory has not been and is not now equipped to
compete in lunar photography with some other observatories;
but it has played a worthy part in the early photometric work,
in making accurate drawings, in investigating lunar geology,
and in experimenting in the photography of the position and
surface of the moon.
The Planets and Their Satellites. Soon after the mount-
ing of the large refractor in 1847, planetary observations were
enthusiastically begun by the Bonds, especially on Saturn, its
rings, and satellites. These were continued for about 10 years,
and led to the discovery of Bond's Dusky Ring and the eighth
satellite, Hyperion. Many other interesting observations of
this system were made, notably at the times when the plane of
the rings passes through the earth and the sun. Charles W.
Tuttle and Sydney Coolidge took part in these observations. 21
During the 20 years from 1857 to 1877, observations of the
planets seem to have languished, except for George P. Bond's
photometric work, and some micrometric measures of the
satellites of Saturn, Uranus, and Neptune, made during 1866 to
1868 by Joseph Winlock, with the assistance of Benjamin
Peirce, Charles S. Peirce, Samuel P. Langley, and George M.
Searle. 22
When Edward C. Pickering took up his duties as director,
early in 1877, he turned his attention not only to the pho-
tometry of the stars, but also to the photometry of some of
10 H. A., 72, No. i, 1911; 76, No. 7, 1915; 80, No. n, 1917; 81, No. 5, 1919;
85, No. 9, 1926.
"H. A., 2, Part i, 1857.
H. A. f 13, Chap. 4, 1882.
THE PLANETS AND THEIR SATELLITES 87
the planets and their satellites, and of some asteroids. The
observations were made at first with the 1 5-inch refractor, but
later different meridian photometers were devised. For use
with the large refractor, photometers of special construction
(chiefly of polarizing type) were employed, made for the most
part under Pickering's supervision. Since much light is lost
in a polarizing photometer, very faint objects (such as the
satellites of Mars, which were discovered by Hall at about that
time) must be observed without the intervention of any absorb-
ing or reflecting media except those of the telescope itself.
The satellites of Mars, therefore, were compared with a starlike
image formed by passing the light of the planet through an
extremely minute hole in a metal screen. A series of observa-
tions of Phobos and Deimos was made in 1877, and again in
1879, by Pickering, assisted by Searle, F. Waldo, and Wendell.
The subject was of wide interest at that time. The positions
of the satellites, also, were measured frequently, and data
were thus furnished for improved orbits of the satellites, and
more accurate determinations of the mass of Mars. 23 Observa-
tions in 1 88 1 to 1882, made with an improved photometer,
gave the mean magnitudes, 14.42 and 14.11, for Deimos and
Phobos, respectively, and 13.13 for the magnitude of Deimos
at mean opposition. 24
At one time or another almost every form of photometer
has been tried at the Observatory. A conjunction of the
planets Mars, Saturn, Jupiter, and Venus, in 1877, afforded an
opportunity to compare their relative magnitudes. No
telescope was employed, as the light was sufficient with the
photometer alone. 25 Photometric measures were also made of
the satellites of Jupiter, Saturn, Uranus, and Neptune. 26
Observations of the planets and brighter satellites and minor
planets were carried out also with the meridian photometers. 27
23 H. A., ii, Chap. 7, 1879; 13, Chaps. 5 and 6, 1882.
* H. A., 33, No. 9, 1900.
25 H. A., n, Chap. 3, 1879.
26 Ibid., Chaps. 8-10, 1879; 69, Chap. 12, 1909.
* H. A., 24, 265, 1890; 46, Chap. 8, 1904.
88 THE SOLAR SYSTEM
The photographic magnitudes and color indices of Venus,
Mars, Jupiter, Saturn, and Uranus have been more recently
determined by King, 28 using the accurate out-of-focus methods
described in Chapter XI.
Eclipses of Jupiter's Satellites. An extensive and impor-
tant research at the Observatory consisted in the observation
of the precise times of eclipses of the satellites of Jupiter.
The determination of these times presents special difficulties,
for the satellites have sensible discs, and therefore the eclipse
is not an instantaneous event, but has considerable duration.
The time consumed by the satellites in entering or leaving the
shadow of the planet varies in general from 4 to 13 minutes.
Hence, with different observers and instruments, using ordinary
methods of visual observation, the recorded times of eclipse
differ by several minutes. To avoid this large element of
uncertainty, Edward C. Pickering undertook in 1878 to deter-
mine by photometric means the moment when the center
of the satellite enters or leaves the shadow. The light of the
eclipsing satellite was usually compared with that of another
satellite. Readings were rapidly made with a polarizing
photometer from the beginning to the end of the disappearance,
or reappearance. Such observations during a period of 25
years, 1878 to 1903, by E. C. Pickering, Searle, and Wendell
form Part i of Harvard Annals, 52, 1907. A discussion of these
observations by Ralph Allen Sampson, Professor of Mathe-
matics and Astronomy in the University of Durham, now
Astronomer Royal of Scotland, was published two years later.
Professor Sampson developed the theory of these eclipses,
corrected existing theories, and discussed the Harvard observa-
tions. He came to the conclusion that various anomalies
which were present were due to the departures of Jupiter's
figure from a perfect spheroid, and that the departures are
probably irregular and transient. 29 Additional visual observa-
28 H. A., 59, No. 10, 1912; 85, No. 4, 1923.
* H. A., 52, Part 2, 1909.
PLANETARY OBSERVATIONS BY W. H. PICKERING 89
tions of the eclipses were made by Wendell from 1903 to 1912,
the year of his death. 30
Photographic observations of the eclipses of Jupiter's
satellites were made by Edward S. King from 1888 to 1898, with
the n-inch Draper refractor. He obtained many series of
images of Jupiter and its satellites taken at intervals of 10
seconds. On plates thus taken the image of the eclipsing
satellite gradually disappears or reappears, and the moment
of half brightness can be determined. A comparison of the
results of these observations with those of the visual photo-
metric observations referred to above shows that in general
for satellites I and II, the photographic determination of the
time is somewhat later than the visual for disappearance, but
earlier for reappearance. The fogging of plates by halation,
due to the bright image of Jupiter, greatly increased the diffi-
culties encountered in their reduction. 31 King also photo-
graphed several lunar occultations, including some of Saturn,
by a somewhat similar method. 32
Planetary Observations by W. H. Pickering. For many
years William H. Pickering has given much attention to plane-
tary observations. At Arequipa, in 1891 to 1892, he undertook
observations of an artificial disc, in order to determine, in
ordinary observations of the planets, the errors due to irradia-
tion, poor definition, and other causes. A large disc, 8 feet
in diameter, on whose surface were painted black lines, dots,
and crosses, was placed on the flank of Mount Chachani, at
an altitude of about 16,600 feet, and at a distance of 11.25
miles. The results, however, were not altogether satisfactory,
since the observations on the artificial disc were made in the
daytime and were influenced by poor seeing and other condi-
tions. Similar observations were later carried on at Cam-
bridge. Many observations, too, were made by W. H. Picker-
30 H. A., 69, Chap. 13, 1912.
81 H. A., 80, No. 10, 1916.
M H. A., 59, No. 7, 1912.
90 THE SOLAR SYSTEM
ing and Douglass on the surface markings and other peculiarities
of Mercury, Venus, Mars, Jupiter, and Neptune. Among the
conclusions drawn from these observations were: the periods
of rotation and revolution of Mercury must be nearly, or quite,
equal, and the planet's atmosphere is extremely rare; the
diameter of Venus was found to be 7662 miles, and her atmos-
phere is probably many times as dense as that of the earth.
Pickering and Douglass observed no color in the atmosphere of
Venus. The diameter of Neptune was found to be 2 ".30, a
value somewhat less than that previously found by most
observers, but in agreement with later determinations. The
ellipticity of Jupiter's satellites also has received much
attention. 33
The Ninth Satellite of Saturn. From an examination
of Bruce plates made at Arequipa, William H. Pickering dis-
covered in 1899 a ninth satellite of Saturn. This discovery was
not an accident, but the result of a definite plan and long
search. The name " Phoebe" was appropriately assigned to
the new satellite by Pickering, thus adding the name of another
member of Saturn's family. The orbit was found to be
elliptical, and a study extending over several years revealed
the fact that the motion of the satellite is retrograde. This
was unexpected at that time, but later the motion of two of
the outer satellites of Jupiter, discovered by Perrine, was also
found to be retrograde. Pickering also found certain extremely
faint images on the Bruce plates, which he attributed to the
presence of a tenth satellite of Saturn. To this object he gave
the name " Themis." The reality of the tenth satellite,
however, has never been confirmed elsewhere, and until this
is done by an independent investigator, the existence of Themis
must be considered doubtful. 34
The Surface of Mars. Many observations have been
made, and numerous papers written concerning the surface
M H. A., 32, Chaps. 4 and 5, 1900; 61, Chap. 6, 1908; 82, No. 4, 1923.
84 H. A., 53, Nos. 3, 5, 6, and 9, 1905; 60, No. 3, 1908; 61, Chap. 7, 1908.
THE TRANSNEPTUNIAN PLANET 91
markings and physical conditions of the planet Mars, by
W. H. Pickering. The greater part of this work has been
published in astronomical journals, especially in Popular
Astronomy. Several investigations, however, appear in the
Annals; one, on Martian Meteorology, is a study of the tem-
perature, cloudiness, seasonal changes, and atmospheric
circulation, based chiefly on photographs of the planet made
at Arequipa in 1888 and iSpo. 35 Many determinations of
the positions of various points on the surface of Mars were
made during the oppositions of 1914, 1916, 1918, 1920, and
1922. On these were based the paper "Location of a Hundred
Points on the Planet Mars." It is illustrated by a map showing
the positions of the well-determined points. 36
The Transneptunian Planet. W. H. Pickering undertook
to investigate by graphical methods the evidence in favor
of the existence of a transneptunian planet. The possible
existence of such a planet had been in the minds of astronomers
for a long time, and several attempts had been made to discover
it. After a preliminary discussion of the perturbations caused
by Neptune on Uranus, Saturn, and Jupiter, Pickering con-
sidered the perturbations caused on Uranus and Saturn by
some unknown planet, and the influence of such a planet on
Neptune. Elements were derived for the unknown trans-
neptunian planet, which he designated by O. 37 Two years
afterward he located, by means of cometary statistics, three other
planets exterior to it; he believed them to be extremely massive
and very remote. 38
A revision of these results, made several years later, gave a
summary of similar researches made by other astronomers.
Revised elements for Planet O were derived, but an examination
of photographic plates gave negative results. Similar examina-
tions elsewhere had no better outcome. If such a planet
88 H. A., 53, No. 8, 1905.
88 H. A., 82, No. 5, 1924.
87 H. A., 61, Part 2, 1909.
88 H. A., 61, Part 3, 1911.
92 THE SOLAR SYSTEM
exists it is doubtless rather faint, perhaps of the twelfth mag-
nitude or fainter. Had it been as bright as the eighth or
ninth magnitude, it could hardly have escaped detection so
long. 39
The Asteroids. Occasional observations of asteroids have
been made by members of the Observatory since 1866. During
Winlock's administration, the positions of a number of aster-
oids were determined. 40 In 1877, E. C. Pickering, assisted
by Searle and Upton, began photometric observations of
the brighter asteroids in connection with the photometry of the
stars, 41 and photometric observations were made with the
Meridian photometer from 1882 to 1888. 42
Henry M. Parkhurst of New York, in association with
the Observatory, made a valuable contribution to the pho-
tometry of asteroids in 1887 and 1888. His long series of
photometric observations were of special interest in showing
the relation of phase to brightness. 43 Searle found that these
results had an important bearing on his discussion of the
brightness of the zodiacal light and Gegenschein. 44 Park-
hurst continued his observations until iSSg, 45 and E. C. Picker-
ing's conclusions based on Parkhurst's measures compared
well with those obtained in Germany by Mtiller. Both found
independently, and by different methods, that the effect of
the phase upon the magnitude of an asteroid is sensibly pro-
portional to the angle determining the phase, an unexpected
law of variation, conforming to no theory that had been
proposed. 46 These conclusions were confirmed by observations
made with the large refractor by Searle and Wendell. 47
H. A., 82, No. 3, 1919.
40 H. A., 13, Chap. 7, 1882.
41 H. A., II, Chap. 12, 1879.
H. A, 24, 264, 1890.
H. A., 18, No. 3, 1890.
"H.A., 19, 235, 1893-
H. A., 29, No. 3, 1893.
46 Ibid., Appendix.
c H. A., 33, No. i, 1900.
VARIABILITY OF EROS 93
Several new asteroids have been discovered on the Harvard
photographs, and doubtless others, not yet noticed, are present
on the plates, besides many trails of known asteroids. Ocllo,
(475), discovered at Arequipa in 1901 by Stewart on a Bruce
plate, is an especially interesting object. The inclination of
its orbit is considerable and the eccentricity is larger than that
of any asteroid known at that time.
Reverend J. H. Metcalf, in his private observatory, which
was long associated with the Harvard Observatory, discovered
several new asteroids with photographic telescopes of his own
construction.
Variability of Eros. Eros, , though small in size, is in
many ways the most interesting of the asteroids. It was
discovered in 1898 by Witt. At times it comes nearer to the
earth than any other known celestial body except the moon.
Such times, however, are rare. One occurred in 1894, four
years before the discovery of Eros. Fortunately, its path in
1893 an d J ^94 became well known from an examination of the
photographs in the Harvard collection. An accurate deter-
mination of its orbit was thus possible without delay. At
times of close approach, the parallax of Eros, and hence indi-
rectly the parallax of the sun, can be determined with a^high
degree of accuracy. 48
Early in 1901, Oppolzer announced the variability of the
light of Eros, which was promptly confirmed by several observ-
ers. It was found to have a period of about five hours, or
perhaps one-half that length. Wendell found that its range of
variation was i.i magnitudes on March 12, 0.4 magnitude on
April 12, and less than o.i on May 6. 49
During the opposition of 1903 to 1904, systematic photo-
metric observations of Eros were made at Arequipa by S. I.
Bailey. Both visual and photographic methods were employed.
The variations in light were clearly shown by the visual observa-
H. A., 53, No. 10, 1005; H. C. 34, 1898; 36, 1898; 37, 1899; 51, 1900.
A. N., 155, 309, 1901.
94 THE SOLAR SYSTEM
tions, and were amply verified by the photographic obser-
vations on Bruce plates. The double period, 0.2196 day, was
found to satisfy all the observations. The range of variation
appeared to change slowly and uniformly, during the time
covered by the observations, the range varying from one-half
to three-quarters of a magnitude. Photometric observations
were also made of 22 other asteroids, five of which showed
evidence of variability. 50
Investigations on the light curve of Eros in 1914 were
made by Margaret Harwood, Director of the Maria Mitchell
Observatory. From an examination of all available data,
including photographs made at the Harvard, as well as at the
Maria Mitchell Observatory, she found a variation of about
0.3 magnitude in the light of Eros, and an apparent period of
0^.3064 instead of 0^.2196, as previously found. 51 Later Miss
Harwood made an exhaustive summary of all the data in
regard to Eros and other variable asteroids, and discussed
theories in regard to the variations. 52
Discovery and Observation of Comets. The establish-
ment of the Harvard Observatory on a sound foundation was
due, as shown elsewhere, to the deep public interest in the
great comet of 1843. Indeed, there has always been a popular
demand for information in regard to new or brilliant comets.
It was natural, therefore, that the early members of the Observ-
atory staff should give them considerable attention. Alto-
gether, a number of new objects were discovered; and much
time has been spent in their observation, and in the computation
of orbits. George P. Bond's monograph on Donati's comet
of 1858, a work which has been called an astronomical classic,
contains many elaborate drawings and diagrams of the physical
appearance of the head and tail of the comet, and a large
collection of data from various sources. 63 Comets were the
60 H. A., 72, No. 5, 1913.
61 H. A., 76, No. 8, 1915.
" H. C. 269, 1924.
" H. A., 3, 1862.
DISCOVERY AND OBSERVATION OF COMETS 95
first occasion for the astronomical telegraph service, for which
the Observatory became the center.
For many years, beginning about 1880, a large amount of
volunteer work was done by Seth C. Chandler, a remarkably
rapid computer, who would carry through the computations
necessary to the announcement of the elements of a new orbit,
with little or no regard for rest or sleep. Similar work was
later carried on by Wendell. Observations of comets were
made by Winlock, C. S. Peirce, G. M. Searle, and Wendell,
during the years 1867 to i88i. 54
A study of Comet Swift, 1892, was made by W. H. Pickering
from photographs taken at Arequipa with various instruments.
From an examination of these photographs Pickering concluded
that the comet revolved about a longitudinal axis in a period
of about four days. He also drew attention to the " electrical
nature of the phenomena exhibited," and made a detailed
comparison of these phenomena with terrestrial auroras. 55
Photometric observations of the intensity of the light
of different parts of several comets, which appeared from 1879
to 1893, were made by E. C. Pickering, Searle, and Wendell. 56
A statistical investigation of nearly 500 comets and reappear-
ances of comets, which have been well observed during the last
2000 years, was made by W. H. Pickering. The orbits of these
comets were classified in different ways, and Jupiter's "family"
of comets was discussed. When the comets are classified
according to their aphelion distances, the influence of an
unknown planet, Q, beyond Neptune, is indicated. Mr.
Pickering explains "how we may compute the distance, eccen-
tricity, and longitude of perihelion of a planet that has never
been seen." To explain the various groups of comets, planets
P, Q, and R are assumed, as well as a transneptunian planet,
O. A photographic search for Planet was made in 1911 with
negative results. 67
M H. A., 13, Chap. 8, 1882.
M H. A., 32, Chap. 10, 1900.
M H. A., 33, No. 8, 1900.
* H. A., 61, Part 3, xgix.
CHAPTER VIII
TERRESTRIAL PROBLEMS
As part of its work on members of the solar system, the
Observatory has carried on researches on the earth in its rela-
tion to the rest of the celestial bodies. These researches have
fallen into four groups: studies of meteors in their paths
through the upper atmosphere of the earth; meteorological
studies of the lower atmosphere; work on terrestrial magnetism;
and geodetic work for the accurate location of positions on the
earth's surface.
The Study of Meteors. No systematic study of meteors
was undertaken for many years after the foundation of the
Observatory. Occasional notes occur, however, in the records
of different observers regarding the appearance of especially
brilliant meteors, or fireballs, which could not fail to attract
attention. The most famous of these was the fireball of
September 30, 1850, which was seen by Jenny Lind as she sat
at the eyepiece of the new 1 5-inch refractor. This meteor was
also observed by William Mitchell at Nantucket and by many
others. 1
From 1884 to 1888, O. C. Wendell published in the Sidereal
Messenger computations of radiant points from which meteors
following the orbits of known periodic comets should appear
at certain dates. Similar papers by him appeared in the Astro-
nomische Nachrichten in 1886, in Astronomy and Astrophysics
in 1892, and in Popular Astronomy in 1908. In several cases
an intimate relation was shown to exist between the orbits
of meteors and known comets.
1 Annual of Scientific Discovery, 1851.
96
THE STUDY OF METEORS 97
The Leonid shower had become conspicuous from its brilliant
apparitions in 1833 an d 1866. E. C. Pickering was active in
promoting a systematic study of its return in 1899. Its
appearance in 1833 ^ a d been a most striking exhibition, and
although it was somewhat less so in 1866 and 1867, a brilliant
spectacle was expected in 1899. As showers, however, might
occur one or two years earlier or later, the program was arranged
to begin in 1897 an d cover the period 1897 to 1899. A compre-
hensive scheme of observations was made out, a map of the
region of the Leonid radiant was prepared, and the cooperation
of observers in all parts of the world was secured. The work
of 1897 was both visual and photographic; members of the
Observatory occupied stations at Cambridge and on Blue Hill,
and 138 meteors were observed. The results were discussed in
the Harvard Annals by W. H. Pickering. 2
The work at the return of the shower in 1898 was largely
photographic. On November 14, 96 photographs were
taken at Cambridge with the Draper n-inch equatorial and
with n smaller instruments. Two cameras were taken to
Tufts College, and 25 simultaneous photographs were taken at
both stations. In all, 34 trails of n different meteors were
photographed a remarkable collection of data for a single
night's work. 20 Attempts to photograph the spectra of these
meteors failed. 3
Extensive preparations were made for the expected return
of the Leonids in November, 1899. The world-wide organiza-
tion of observers was complete, and at the Observatory prepara-
tion was made for both visual and photographic observations.
The Leonids, however, failed to appear in considerable numbers,
and no results deemed worthy of publication were obtained. 4
In the years immediately following, comparatively few meteors
2 H. A., 41, No. 5, 1902; H. C. 31, 1898.
2a The Harvard data have only recently been discussed by Dr. Fisher in Har-
vard Bulletin 870, 1930. The data obtained at Tufts College are till unpub-
lished.
'H. .35,1898; 40, 1899.
g8 TERRESTRIAL PROBLEMS
appeared in Cambridge although observations were made in
1901 and I9O4. 8 Rather brilliant Leonid showers, however,
were reported from other parts of the world. 6
W. H. Pickering contributed occasional articles in later
years on meteors and meteor theory to the Astrophysical
Journal and to Popular Astronomy, and took an important
part in the discussion of the " meteoric procession " of February
9, 1913. This remarkable event was observed from Saskatche-
wan to the South Atlantic, and was caused by a long, narrow
swarm of bright meteors which followed an apparently curved
path through the upper atmosphere at heights which seemed
to change little in all that long journey. 7
Occasional meteor trails occur on the astronomical photo-
graphs in the Harvard collection. These plates were generally
taken as stellar charts or spectrum plates, and the meteor
trails are fortuitous. During the years while Mrs. Fleming was
busied with the examination of these plates, she made a
record of 91 meteor trails and four meteor spectra. Some of
these were placed on exhibition as illuminated transparencies.
The first systematic examination of any of the Harvard plates
for the special study of meteors, however, appears to have been
begun in 1922 when Miss Ames and Miss Howarth, under Dr.
Shapley's direction, undertook an examination of 2000 plates
made with a Cooke lens of about one inch aperture, having
exposures of one hour. More exactly, the 2000 plates had a
total exposure of 2297 hours. Four sets of regions and time
intervals were so chosen that each included the radiant point
and date of a known meteor shower. The total number of
meteors found was 24, "indicating the great rarity of meteors
sufficiently bright for detection by the patrol telescopes as
ordinarily used in charting stars to the eleventh magnitude." 8
H. C. 89, 1904.
8 Pop. Astr., 10, 400, 1902.
7 Pop. Astr., 30, 632, 1922; 31, 96, 443, 501, 1923- A recent rediscussion of
the data by Dr. W. J. Fisher, published in Harvard Reprint 47, 1928, interpreted
all the observations satisfactorily for the first time by taking into account the
equatorial rotation and bulge of the earth.
8 H.B. 788, 794, 1923.
PLATE XI. (Top) SPECTRUM OF A METEOR. (Photographed with the
Bruce Telescope.) (Middle) MULTIPLE METEOR TRAIL. (Bottom) SPECTRUM
OF LIGHTNING.
(Facing page 98)
U
u
THE STUDY OF METEORS 99
At about the same time King determined the Orionid radiant
very exactly from three trails found on a single plate. A
parabolic orbit for the Orionid meteors was also computed
by the method of Bauschinger, using the 1900 and 1922 positions
of the radiant. 9
In 1925, a grant for meteor work at the Observatory was
made by the J.Lawrence Smith Fund Committee of the National
Academy of Sciences. Under this grant work was undertaken
by Dr. Willard J. Fisher, and is still in progress. Some account
of its scope is indicated in the following summary.
a. Discovery, Measurement, and Study of Meteor Trails on the
Harvard Plates. An examination of 71,454 plates made with
different instruments yielded 213 meteor trails. The total
number of such trails is now known to be at least 360; another
illustration of the rarity of such trails on photographic plates
of the sky a result of the rapid motion of the meteors. But
the photographic data compensate for their fewness by their
accuracy; each is an authentic record of an air path; and
knowledge of meteors is largely based on air paths.
b. Promotion of the Study of Fireballs. Interest in fireballs
is aroused by the circulation of questionnaires in the daily
press and by radio, whenever any notable fireball of the sort is
reported and by subsequent popular publication of the results;
the answered questionnaires received from numerous amateur
observers are studied and discussed and the results are published
and circulated in the scientific press and as abstracts in the daily
papers. Among the phenomena which were thus handled at
the Observatory were the fireballs of November 15 and December
29, 1925, and August 10 and October 16, 1927.
c. Theoretical and Critical Study of Meteoric Problems.
Attempts are made to promote the gathering of precise photo-
graphic data on the air paths of meteors. Only thus can the
evanescent changes in the air paths be recorded for measure-
ment, or spectrum records be obtained, so essential for the
understanding of the physical processes which accompany the
9 H. B. 778, 1922; 783, 1923.
100 TERRESTRIAL PROBLEMS
destruction of one of these solids. Photography cannot
replace the eye in meteor observations, but the two methods
supplement each other. 10
Meteorology. One result of the assiduous study of meteors
will be the increased knowledge of the upper atmosphere. The
lower atmosphere, within reach of our recording instruments,
is still a problem which astronomers must take into considera-
tion. In seeking sites for astronomical observing stations long
series of meteorological observations are needed. At the
present time there is an abundance of independent mete-
orological observatories or stations. A century ago, however,
such separate observatories were rare, and meteorological
observations were often undertaken by astronomical observa-
tories, including the Harvard Observatory as a logical part of
their work. 11
Extended meteorological observations were early undertaken
at the Dana House Observatory. So important did this line
of investigation appear to the first director, William C. Bond,
that in his Annual Report for 1849 he made the following
statement:
It has for a long time been a subject of regret among those interested
in meteorology and terrestrial magnetism, that there was not within the
limits of the United States a single regularly organized Meteorological
Observatory, where a continued and systematic course of observation
was pursued, such as might serve for a point of departure whence differ-
ences might be reckoned, and where instruments intended to be used on
surveys and explorations might be verified by standards indicating the
momentary condition of the atmosphere and the magnetism of the earth.
We are now in a condition to furnish all the instruments required for
such an establishment, and need only a suitable building for their accom-
modation, such as would be afforded by the erection of the western wing
of our Observatory, according to the original design. 12
10 H. B. 845, 849, 852, 853, 1927; 854, 1928; Pop. Astr., 34, 421, 1926; Proc.
Nat. Acad. Sci., 12, 728, 1926; 13, 540, 578, 1927; Journ. R. A. S. Can., 20,
225, 1926; Science, 64, 507, 1926; 66, 507, 1927.
11 See pp. 18, 34.
12 H. A., I, cxxxix, 1856.
METEOROLOGY IOI
The plan of establishing an associated meteorological
observatory was never completely carried out; nevertheless,
systematic meteorological observations were made in Cambridge
for nearly half a century. 13 Later, the establishment of the
closely associated Blue Hill Meteorological Observatory
rendered unnecessary a continuance of laborious meteorological
observation at the Cambridge Observatory. Until 1888 the
data were collected continuously. They were reduced and
discussed by Arthur Searle, and were published in the Annals,
together with notes on auroras and thunderstorms. 14
The Blue Hill Meteorological Observatory was founded
by A. Lawrence Rotch in 1885, as a private institution. It
soon became one of the best equipped meteorological stations
in the United States and its relation to the Harvard Astro-
nomical Observatory was very intimate. After its establish-
ment it became apparent that the Harvard Astronomical
Observatory could be of greater service to science by under-
taking the publication of the Blue Hill results than by an
extension of its own meteorological work. An arrangement
was therefore concluded by which the Blue Hill observations
appeared in the Annals of the Astronomical Observatory of
Harvard College. Rotch became a member of the Harvard
staff, and the ultimate union of the two institutions was
contemplated. On the death of Mr. Rotch in 1912, however,
the Blue Hill Meteorological Observatory, which he had left
by will to the University, was made a separate department
by the Corporation. Nevertheless, from 1889 to 1927 ten
volumes of the Annals were devoted to the results obtained
at the Blue Hill Meteorological Observatory. These included,
in addition to the usual tables of meteorological observations,
a large variety of papers discussing different phases of the
"Partial reports: Mem. Amer. Acad., 1846; American Almanac, 1844 to
1857; Patent Office Reports, 1856 to 1859.
14 H. A., 19, Part i, 1889.
16 H. A., 20; 30; 40; 42; 43J 58; 68; 73; 83; 86, Parts i, 2, and 4; 87, Part i.
102 TERRESTRIAL PROBLEMS
For the further encouragement of meteorological science,
cooperation was established with the New England Mete-
orological Society in the publication of its results during the
years 1888 to 1895, 16 and the observations of the United
States Signal Service on the summit of Pikes Peak, Colorado
(altitude 14,134 feet), from 1874 to 1888 were also published
by the Observatory. 17
In 1887, under the Boyden Fund, extensive series of meteor-
ological investigations were undertaken for the purpose of
determining the best site for an astronomical station, either
in the northern or southern hemisphere. Personal visits
were made to Colorado and California, and correspondence
was opened with the officials of the Central and Southern
railways of Peru, which reach high altitudes. After the
establishment of the Boyden Station at Arequipa, Peru,
regular meteorological observations were maintained from 1891
to 1927. In addition to the observations at Arequipa, a
number of secondary meteorological stations were maintained
for several years, extending from Mollendo on the Pacific
Ocean over the western Andes to the Titicaca Plateau, and
beyond the eastern Andes to Santa Ana in the valley of the
Urubamba River. This line of stations reached its highest
point at the station established in 1893 on the summit of El
Misti, at an elevation of 19,200 feet. The results obtained at
these stations constitute an important contribution to mete-
orology in a region where few observations had previously been
made, and at altitudes seldom if ever attained. 18
Terrestrial Magnetism. Isolated though important obser-
vations in terrestrial magnetism had been made for several
centuries, but the subject was first made international and
handled in a strictly scientific manner only a few years before
the foundation of the Harvard Observatory. Humboldt
erected the first magnetic observatory at Berlin in 1828.
16 H. A., 21 ; 31 ; 41, Nos. 1-4.
17 H. A., 22.
H. A., 39 J49; 86, Part 3.
TERRESTRIAL MAGNETISM 103
In 1833 Gauss, in his theoretical study of the earth's magnetism,
finding his progress stopped by the want of accurate and
extensive data, founded a magnetic observatory at Gottingen.
A little later Humboldt asked aid of the Royal Society of
London, which made an appeal to the English-speaking world
for more extended observations. This appeal was answered
by the magnetic observatory in Philadelphia and by the recently
established Observatory at Cambridge, A suitable equipment
of magnetic instruments was provided through a grant of the
American Academy of Arts and Sciences.
The scheme of simultaneous observations first arranged
by the Royal Society for the different stations was designed to
cover the three years 1840 to 1842. Work was begun at the
Dana House Observatory in March, 1840, with the Gauss
magnetometer of Mr. Bond; and later the observations were
extended to the three newly arrived magnetometers provided by
the American Academy. The observations were continued
until March, 1843.
The plan of the Royal Society prescribed that the declination
magnetometer and the horizontal and vertical force instru-
ments should each be observed once every 2 hours during the
24 hours on every day of the year. One day in each month
was set apart for observations with the three instruments
at shorter intervals. On these days, called " term-days/'
the declination magnetometer was to be read every 5 minutes
and other instruments every 10 minutes, making in all 576
observations during the day. All these observations were
made by volunteer observers. The death of William C.
Bond, Jr., in 1841, increased the difficulties encountered in
securing such continuous observations without paid assistants.
During some of the period, the work was superintended and
the results discussed in part by Professor Lovering, assisted
by Professor Benjamin Peirce. 19 During this period also
the student members of "The Meteorological Society of
Harvard University/' assisted in the work at the Observatory,
19 Mem. Amer. Acad., New Series, 2, i, 85, 1846.
104 TERRESTRIAL PROBLEMS
which included a time service and detailed meteorological
observations. The observations showed the extreme com-
plexity of the magnetic variations, the small diurnal range in
declination and its irregularities, and the effects of solar cycles,
and auroras.
Additional observations for a second period of years were
proposed by the Royal Society. Owing, however, to the
engrossing nature of the observations, the lack of paid assistants,
and the press of other work, Mr. Bond was forced to decline
participation in a second campaign at that time, and such
observations have never again been taken up at the Observa-
tory. America, however, has made large contributions to
the study of terrestrial magnetism, especially by the many
and widely separated stations of the United States Coast and
Geodetic Survey, and by the work of the Carnegie Institution
under the direction of Dr. L. A. Bauer.
Geodesy. During its early years, the Observatory was
closely associated with geodetic work. Both before and after
his connection with the Observatory, William C. Bond was in
official relation with the United States Coast Survey. At
that time, Boston, that is, the " Cambridge Observatory,"
was generally regarded as the best determined position in
America, and the center to which other positions were referred.
The report of the Visiting Committee for 1856, under the
chairmanship of Robert C. Winthrop, stated that:
... it may be understood from various papers contained in the
Reports of the Superintendent of the Coast Survey that the longitude of
all the principal positions in the United States are dependent on the
longitude of the Harvard Observatory. 20
The accepted longitude of Harvard was not based upon
the recent chronometer expeditions, but depended primarily
upon the long and careful series of longitude determinations
made by William C. Bond by observations of eclipses, transits,
H. A., I, clxxxiv, 1856.
GEODESY 105
occultations, and moon culminations. The reliability of these
results had been appreciated as early as 1845 by t* 16 American
and British Commissions in charge of the Survey of the North-
eastern Boundary, which made use of Bond's results. His
value of the longitude was only slightly modified by the chro-
nometer campaigns of 1849, 1850, 1851, and 1855, and only
slight additional modifications in the position of the Observatory
have resulted from more recent determinations of the longitude
by the telegraph and by radio.
The longitude of the Sears Tower, West of Greenwich, as
determined by Bond's long series of observations and by many
chronometer expeditions, was 4* 44 30*. 7. The following
differences in longitude were derived from the Massachusetts
and United States surveys:
East of Sears Tower
The Observatory at Dorchester 14". 776
The Observatory at Dana House 3 . 098
Cupola of State House, Boston 15 . 525
In 1844 and 1845 Colonel James B. Graham, Chief Astronomer
and Surveyor of the Northeastern Boundary Commission,
participated with the Bonds in the determination of the latitude
of the new Observatory. 21 The latitude of the Sears Tower was
north 42 22' 48".!. The following differences in latitude were
also derived from the Massachusetts and United States surveys:
South of Sears Tower
The Observatory at Dorchester (W. G. Bond) 3' 37". 49
Old Observatory at Dana House 31 .82
Cupola of State House, Boston i 23 .89
The present accepted values of the latitude and longitude of
the Sears Tower are:
Latitude +42 22' 47".6; longitude 4* 44 3i*.o5. 22
After the position of the Observatory had been determined
with all possible precision, less attention was given to geodetic
problems. The Observatory has always been ready, however,
21 Benjamin Peirce, Mem. Amer. Acad., New Series, 2, 183, 1846.
w H. A., i, xvii, 1856.
106 TERRESTRIAL PROBLEMS
to cooperate in geodetic work. For instance, in 1888, when
Professor Mary E. Byrd desired to determine the longitude
of the Smith College Observatory at Northampton, Massachu-
setts, the use of the Russian Transit, sidereal clock, and chrono-
graph was extended to her. Corresponding instruments
were used at the Smith College Observatory. Miss Byrd was
assisted by Professor Mary W. Whitney, of Vassar College.
Telegraphic signals were exchanged between the two stations
on six nights, the observers exchanging stations after the third
night. The position of the Russian Transit, as determined at
that time, was 4 h 44 m 3i s .o$$. The difference in position be-
tween the Russian Transit in Cambridge and the Smith College
Observatory was found to be +6 m 2 8 .o63, giving 4^ 50^3*. 096,
as the longitude of the latter station. 23
The latitude and longitude of the Boyden Station of the
Observatory at Arequipa, Peru, was determined in 1896 to
1897, under Professor Winslow Upton, by the regular staff of
the station as described in Chapter V. The determination
of the latitude was made by transits in the prime vertical,
using the Rogers Transit of the Arequipa Station. The mean
result of observations made on several nights was 16 22'
28".o. A preliminary determination of the longitude was
first made by moon culminations, as well as by a partial solar
eclipse, and by a chronometer carried from New York to
Arequipa in July, 1896. The means of the three methods gave
a provisional value of 4 h 46 12.
Difficulty was encountered in obtaining the necessary tele-
graphic connection between Arequipa and Arica by the land
route, and the cable from Mollendo was used instead. This
required the use of a relay at Mollendo, where the necessary
duties were performed by Mr. Clymer.
At Arica the longitude of the church spire, la Iglesia Matriz
is 4* 41 m 19^.991, as determined by Lieutenant Commander Davis.
The transit pier used by Upton was near the church.
The results of the campaign gave:
23 H. A., 29, No. 2, 1893.
GEODESY 107
Longitude transit pier at Arica, West of Greenwich 4* 41**. 19* .90
Difference in longitude of Arica and Arequipa +4 51 .83
Longitude of Arequipa, transit instrument 4 46 n . 73
Professor Upton also made a determination of the altitude
of the Boyden Station above sea level, by the use of the railway
survey and the measured difference in altitude between the
railway at Arequipa and the Boyden Station. The resulting
altitude is 2451.4 meters, or 8043 feet. 25
At the request of the Canadian Government, a longitude
campaign between the Ottawa and Harvard Observatories was
conducted in 1905 by Dr. Otto Klotz, at that time in charge of
the Canadian Survey. The important series of longitude
determinations carried on by the Canadian Government,
extending completely around the world, was thus connected
with the extensive system in which the Harvard Observatory
has been a part. A small transit building was erected for this
work after consultation with Dr. Klotz and the Superintendent
of the United States Coast and Geodetic Survey. This shelter
has remained as a permanent feature of the Observatory
grounds, and has been found useful by officials of the govern-
ment in later investigations.
25 H. A., 48, No. 9, 1903.
CHAPTER IX
ASTRONOMY OF POSITION
ASTROMETRY, the astronomy of position, was at one time
the main concern of nearly all astronomical observatories. The
chief interest of astronomers was centered on the movements
and influence of the sun and planets, and the positions of the
" fixed " stars were needed as points of reference; or, if the stars
were not fixed, then their motions also were required in order
to determine their precise positions at any time. Although
astrophysics, leading the way to stellar evolution and other
cosmic problems, has usurped the leading place in interest
today, astrometry still plays an important r61e. It has
occupied a prominent place in the work of the Harvard Observa-
tory since its foundation to the present time.
The Bond Zones. Owing to lack of suitable instruments,
few observations for precise positions of the stars were under-
taken with meridian instruments until the arrival of the 8-inch
meridian circle obtained by Winlock in 1870. The chief work in
astrometry during the early years of the Observatory was the
observation of the faint stars in the zone from declination o oo'
to +1 oo'. The observations were made with the i5-inch
equatorial refractor, and were begun by George P. Bond in
1852 and carried out with the assistance of C. W. Tuttle, Safford,
and Coolidge. A few observations were made by W. C. Bond.
The recorder was usually Tuttle during the years 1852 to 1859,
but during the remainder of the period 1859 to 1861 Asaph
Hall was recorder.
The methods of observation need a brief explanation. A very
thin sheet of mica, through which the stars were readily seen,
was placed in the focus of the telescope. A series of lines
108
THE BOND ZONES 109
were engraved on the mica, dividing the field of the eyepiece in
declination into 66 equal divisions, each having a value of
10". Perpendicular to these were two lines so spaced as to
represent 4* at the equator. Each series, or zone, consisted
of the stars in about two hours of right ascension, and 10'
in declination. After the zero of right ascension had been
determined, the telescope was firmly clamped and remained
fixed in position until the conclusion of the zone. The stars
to be observed, which on the average entered the field of view
at the rate of about two a minute, were observed as they trailed
through the field. The declination of a star could be estimated
readily to the nearest second of arc, and the observation was
recorded by an assistant. The transits of the star across the
vertical lines gave the position in right ascension, and were
recorded on the chronograph, at that time a newly completed
device not in general use. Each star was usually observed on
two nights. An extended account was given by Bond of the
methods and formulae employed in the reduction of the observa-
tions. Standard stars were selected from all the lists available;
the zones, however, contained about 14 new stars to i standard
star. These zones were published in three parts, the first
containing stars from the equator to declination +0 20' the
second, from +0 20' to +0 40', and the third from +0 40' to
+ 1 oo'. In all, the zones contained over 16,000 stars, 1 of
which about 2000 were duplicates.
The above zone observations were made between the years
1852 and 1861. In 1912, Professor Pickering and Miss Har-
wood, recognizing that this material offered an unusual oppor-
tunity for the determination of the proper motions of faint
stars from visual observations, prepared a plan for reducing all
the measures to a homogeneous system. The Nicolajew zone
of the Astronomische Gesellschaft contains 1756 stars of the
Bond catalogues, and the positions are more accurate than
those available to Bond. Pickering and Miss Harwood reduced
the Bond observations to accord with the more precise positions,
1 H. A., i, Part 2, 1855; 2, Part 2, 1867; 6, 1872.
110 ASTRONOMY OF POSITION
and carried them all forward to the epoch 1875.0. The new
positions, therefore, are those of the dates of observation, so
far as the proper motion is concerned, but reduced to the system
of the Nicolajew Catalogue. 2
Transit Observations. A small transit instrument was
mounted in the east wing in 1848 by W. C. Bond. This
instrument had apparently received some injury during ship-
ment which made it unreliable for observations in declination.
It could be used, however, for determinations of right ascen-
sions, and was so employed by Safford, who observed a catalogue
of standard Polar stars and clock stars for the reduction of
observations in right ascension. Safford also observed a list
of 505 stars in right ascension during the years 1862 to 1865. 3
Micrometric Measures. Many observations of position
were made with a large filar micrometer attached to the 1 5-inch
telescope between the years 1866 and 1872, and similar obser-
vations were occasionally made until 1882. These investi-
gations included double stars, nebulae, satellites, asteroids,
comets, and occultations by the moon. The chief observers
were Winlock, G. M. Searle, and C. S. Peirce. 4
Meridian Circle. The large meridian circle, described
in Chapter IV, was received early in 1870. Transit obser-
vations were begun on November 10 of the same year by
Rogers, who was placed in charge of the instrument. The
early plans for work were formed by Winlock, but the observa-
tions, their reductions, and the discussion of the results were
due to Rogers. The chief undertaking for many years was
the observation and reduction of the zone between the limits
+49 50' and +55 10', the part assigned to the Harvard
Observatory by the Astronomische Gesellschaft in their plans
for the revision of the northern Durchmusterung. While
*H. A., 75, Part i, 1912.
8 H. A., 4, Part i, 1863; Part 2, 1878.
4 H. A., 13, Part i, 1882.
MERIDIAN CIRCLE III
the observation of the Gesellschaft Zone was, perhaps, the
chief object to be attained, it was by no means the only inves-
tigation carried on during the years necessary for its completion.
Begun in 1870, the observations of Rogers and his assistants
were largely completed by 1879, but their final publication
was not finished until 1896. Rogers resigned his position at
the Observatory in 1886 to accept a professorship at Colby
College, but he continued to supervise the reduction and prep-
aration for publication of his observations. Chief among
Rogers' assistants were Mr. Augustus McConnel, and Mr. J. F.
McCormack, principally in recording, and Miss R. G. Saunders,
Miss Anna Winlock, Miss S. C. Bond, Mr. W. Upton, and Mr.
W. V. Brown, in the work of reduction.
The Catalogue of the Gesellschaft Zone is found in Harvard
Annals, 15, Part 2. It gives the precise positions of 8627
stars between +49 50' and +55 10'. The determinations are
differential. The primary stars which were employed in the
reduction of this catalogue and other catalogues, as a result of
the observations of the meridian circle at that time, were
selected from the Catalogue contained in Volume XIV of the
Publications of the Astronomische Gesellschaft. Much time
was given to observations of these primary stars. In addition
several general catalogues were formed for different purposes.
The published results of Rogers' work, which occupy seven
volumes of the Annals, 5 contain elaborate discussions of
all the methods employed in observation and reduction, of
determinations of proper motions, sources of errors, and com-
parisons with other catalogues.
In 1887, Pickering arranged to observe a southern zone
in the plan of the Astronomische Gesellschaft for the revision
of the Southern Durchmusterung. This work was intrusted
to Arthur Searle, who spent the greater part of his time for
about 20 years, with a staff of assistants, in making the necessary
observations, in superintending their reduction, and in dis-
6 H. A., 10, 1871, 1872; 12, 1874, 1875; 15, 1886, 1892; 16, 1886; 25, 1893; 35,
1894; 36, 1896.
112 ASTRONOMY OF POSITION
cussing the results. The observations of this zone, from
9 50' to 14 10', were begun in 1888, and were practically
completed in 1898, although their publication was not concluded
until 1914. The chief assistant in the observations was
Mr. J. A. Dunne, and in the work of reduction, Mrs. Eddy and
Misses Harwood, Hodgdon, Michaelis, Searle, and L. Winlock.
The eight-inch meridian circle, used by Rogers for the observa-
tions of the northern zone, was employed by Searle with few
modifications. When observations were begun with the
instrument in 1870 a system of spider lines was employed, but
was replaced in the following year by a glass plate with etched
lines; this type of glass plate was used until 1900.
The catalogue of the stars of the southern zone contains
refined positions for 8337 stars. It is preceded by an elaborate
description of the methods of observation and reduction. 7
The details of the observations are given in other volumes. 8
In the final volume relating to this southern zone, Searle
made a comparison of his results with other catalogues, using
all accessible lists which contained any considerable number
of stars in the region of the zone; 29 such catalogues were com-
pared. The positions were all reduced to the epoch 1900.0.
It was thought advisable to investigate the systematic differ-
ences which were likely to exist in the different catalogues and
to apply such methods of adjustment as seemed to be
demanded. 9
Searle also made a discussion of the use of geometric methods
in the theory of combining observations, referring to the
methods generally used and the possibility of improving
them. 10
In comparatively recent times, photographic methods for
the determination of position have, to a large extent, taken
the place of the filar micrometer and meridian circle, except
8 H. A., 41, No. 7, 1902; cf. also H. A., 33, No. n, 1900.
7 H. A., 67, 1912.
8 H. A., 62, 65, 66, 1910-1911.
9 H. A., 77, 1914.
10 H. A., 60, No. i, 1908.
THE ALMUCANTAR 113
in the case of fundamental stars. Especially is this true
where only approximate positions are needed. For the
extended lists of new variable stars, nebulae, and the like,
published at Harvard, it has been necessary to give positions
only with sufficient precision to insure the identification of
the objects. When positions are taken from a catalogue,
the simplest procedure is to bring forward the catalogue position
to the desired epoch, but if this is not done, approximate
positions can be rapidly determined from photographs with a
reticle and reading microscope, by measuring the distances
from two or more adjacent stars whose positions are known.
Precise positions also can be obtained from photographs,
and this has been done in some cases. Rectangular coordinates
are often given in place of declinations and right ascensions. 11
The Almucantar. Some reference should be made to the
almucantar, an ingenious invention of Chandler. The accuracy
of his determinations of the right ascensions and declinations
of stars in 1884 an d 1885 rivalled those of meridian circles.
In the almucantar, which floats on mercury, gravitational
action about an imaginary vertical axis is substituted for
motion of rotation about the horizontal axis of a meridian
circle. In Chandler's final instrument a 4-inch telescope
was used. This telescope was first pointed to the east of the
meridian and the time of transit of a star was noted. Later,
the time of transit of the same star was observed to the west
of the meridian. Such observations served for the determina-
tion of time and latitude as well as right ascension and declina-
tion. Chandler demonstrated experimentally that the probable
error of equilibrium must lie within one tenth of a second of
arc, a quantity at the extreme limit of perception, or of indica-
tion by the spirit level. 12
The accuracy of the almucantar observations is well shown
in Chandler's latitude determinations. In observations made
11 H. A., 48, No. i, 1903; 53, Nos. i, 2, 1905; 60, No. 3, 1908.
M H. A,, 17, 1887.
H4 ASTRONOMY OF POSITION
in 1884 and 1885, he pointed out that a curious progression
occurred throughout the series. 13 No explanation for this
change was proposed at that time. In 1891, however, he
published an article in which he showed that his observations
could be interpreted only by a variation in latitude. 14 Mean-
while, Kiistner had announced, in 1888, the variation of
latitude as proved by German observations. Chandler's
later masterly discussion of this subject does not properly
belong to the history of the Harvard Observatory.
The principle of flotation had been recognized as early as
1825, but appears to have been forgotten until Chandler
began his experiments in 1879. Since the latter date various
floating instruments or almucantars have been constructed. 15
13 A. N., 112, 113, 1885.
14 A. J., II, 59, 1891.
16 A. J., 21, 57, 1900; M. N. R. A. S., 60, 572, 1900; 61, 315, 1901.
CHAPTER X
ASTRONOMICAL PHOTOGRAPHY
DAGUERRE announced the success of his experiments in
photography in 1839, only a few months before the old Harvard
Observatory was established at the Dana House. The early
plates, called "daguerreo types " after their inventor, were
formed by sensitizing the polished surface of a silver, or silvered
copper plate, and gave excellent portraits of individuals.
Very long exposures were required, and landscapes, photo-
graphed today in a small fraction of a second, required exposures
of six or eight hours.
Beginnings of Astronomical Photography. The inven-
tion of photography opened the way to astonishing develop-
ments in astronomy, but not at once. Just as the triumph
of Daguerre was the final outcome of nearly half a century
of experimentation by many investigators, so the develop-
ment of photography proceeded for nearly half a century more
before it became a powerful factor in the advance of modern
astronomy.
The three main stages in the progress of photography were
the daguerreotype, the collodion wet plate, and the dry plate.
Bright objects, such as the sun and moon, could be photo-
graphed with the daguerreotype, and later with wet plates.
The astronomical world was obliged to wait, however, for the
slow perfection of the dry plate before photography could be
used extensively in stellar researches.
No sooner had the success of the daguerreotype been
announced in 1839 than Arago suggested its useful application
to astronomical research, confining the suggestion to the sun
and moon on account of the lack of sensitiveness of the early
Il6 ASTRONOMICAL PHOTOGRAPHY
plates. It was in America, however, that Dr. John W. Draper
in the following year (1840) obtained the first photograph
of the moon, with an exposure of 20 minutes. Daguerreotypes
were also used as early as 1842 at total eclipses of the sun, and
the sun itself was photographed in 1845.
From 1849 to 1851, a series of photographs of the moon was
made at the Harvard Observatory, arousing considerable
enthusiasm among astronomers. The photographs were made
with the i5-inch refractor, whose lens was corrected only for
visual rays. The resulting pictures of the moon, although not
in perfect focus, were the best obtained up to that time, though
they could not rival the best visual drawings of the lunar
surface. Indeed, despite all the marvellous photographs
obtained by the giant telescopes of the present day, the rivalry
between visual and photographic observations still persists in
regard to the surface markings of the members of the solar
system, especially of the planets. It is still claimed that
fainter and more delicate details can be seen than photographed.
Progress of Stellar Photography. It is in stellar astron-
omy, however, that photography has made its most important
advances and distanced competition by visual methods it is in
stellar astronomy that the Harvard Observatory has made its
most notable contributions. The first photograph of a star
ever obtained was made at the Harvard Observatory in 1850 by
Whipple, under the direction of W. C. Bond, using a daguerreo-
type plate with the 1 5-inch telescope. An image was obtained
of a Lyrae, magnitude 0.14, and also of a Geminorum,
a double star, magnitude 1.58, whose two components were
indicated by the elongation of the image. No impression could
be obtained of the Pole Star, or of any other star fainter than
the second magnitude, however long the exposure. Instru-
mental and photographic difficulties prevented further experi-
ments at that time.
The investigations were renewed under the direction of G. P.
Bond in 1857 by Whipple and Black professional photographers
PROGRESS OF STELLAR PHOTOGRAPHY 117
) gave invaluable volunteer assistance. A better control
:k had been provided for the 1 5-inch telescope, and the
oduction of the collodion process in photography provided
tes that were more sensitive and more easily manipulated.
April, 1857, images were obtained of Mizar and Alcor on a
;le plate with an exposure of 80 seconds, and images of the
ijhter component could be obtained in from 3 to 5 seconds. A
es of plates of these double stars was made, and a study
the positions and distances of the companion stars was
ried out by G. P. Bond. The results were in close accord
h the visual observations of Struve. Thus it was early
wn that in double star observations photographic methods
Id be expected to yield results rivalling in accuracy the best
lal observations.
n 1850, the limit of photographic attainment had been stars
rhter than the second magnitude; by 1857, the limit had been
*nded to the sixth magnitude. 1 In 1858 G. P. Bond
e the details of further photographic observations of double
*s, concluding with the following sentence:
ideed in every direction the art seems to be susceptible of greater
ection, which may yet render possible its extension, to stars four or
magnitudes beyond our present limit (i.e. to the tenth or eleventh
nitudes). 2
n 1859 Bond demonstrated that a certain time, dependent
the brightness of the star and on other conditions, elapsed
jr the beginning of the exposure before any observable
,ge was formed. He suggested that, instead of the vague
mates of magnitude then made visually (stellar photometry
; unknown at that date), precise determinations of magnitude
e possible by a study of the size and intensity of the photo-
phic images. 3 The three papers on this subject by G. P.
id have been called the classics of astronomical photography,
also wrote an enthusiastic letter on the subject to William
^. N., 47, i, 1857.
L N., 48, i, 1858.
L N., 49. 81, 1859.
Il8 ASTRONOMICAL PHOTOGRAPHY
Mitchell of Nan tucket, in 1857, from which the following brief
quotation is made:
Suppose we are able finally to obtain pictures of seventh magnitude
stars. It is reasonable to suppose that on some lofty mountain and in
a purer atmosphere, we might with the same telescope include the eighth
magnitude. To increase the size of the telescope three-fold in aperture
is a practical thing, if money can be found. This would increase the
brightness of the star images, say eight-fold, and we should be able then
to photograph all the stars to the tenth and eleventh magnitudes, inclu-
sive . . . What more admirable method can be imagined for the study
of the orbits of the fixed stars and for resolving the problem of their
annual parallax than this would be, if we could obtain the impressions of
the telescopic stars to the tenth magnitude!
Henry Draper and the Beginnings of Stellar Spectros-
copy. To trace the development of astronomical photography
in the world at large would involve a long account of the
researches of many distinguished men a subject beyond the
scope of this work. Some reference must be made, however, to
Henry Draper, for his work became intimately associated
with the Harvard Observatory. Dr. Draper followed the
scientific lines begun by his father, Dr. John W. Draper, who
took the first lunar photograph. In 1881, Henry Draper
obtained a photograph of the Orion Nebula on which stars were
shown to the fourteenth magnitude. After about 20 years
of experimental work carried on by many investigators, fairly
reliable dry plates had become available about 1875. The
nebular photograph taken by Draper was perhaps the first
ever made which showed the images of stars as faint as could
be seen with a telescope of equal aperture a result rendered
possible by improvements in the instrument, in the technique,
and in the photographic plates. The photograph, by means
of its power of accumulating the energy falling upon it, had
thus become an instrument of research as powerful as the eye
itself. 4
As early as 1863, Huggins had attempted to photograph
the spectrum of Sirius, but no lines were shown. The first
4 Proc. Amer. Acad., 20, 407, 1885; Washington Obs., 226, 1878.
ASTRONOMICAL PHOTOGRAPHY 119
photograph of a stellar spectrum in which the characteristic
lines were visible was obtained by Henry Draper when in 1872
he took a spectrum of Vega in which four lines were seen. 5
Work of this nature was carried on for some years with slit
spectroscopes by Huggins and Draper but was confined to
bright stars. 6
Astronomical Photography tinder Pickering. Photo-
graphic investigations were again undertaken at the Harvard
Observatory in 1882, under the direction of E. C. Pickering,
assisted by W. H. Pickering, at that time an instructor in
photography at the Massachusetts Institute of Technology.
Instead of the 1 5-inch lens which was uncorrected for the actinic
rays, portrait lenses were employed, at first one of 7 inches
diameter and 37 inches focal length. A long series of experi-
ments was carried out with this and other lenses, attached to
an equatorial mounting, or at rest. As a result of these experi-
ments, a new series of stellar photographs was begun in March,
1885, with a better instrument a Voigtlander lens of 8 inches
diameter and 45 inches focal length, corrected and mounted by
Alvan Clark and Sons. The cost of this equipment was borne
by the Bache Fund, and the telescope was called the "Bache
Telescope/' So successful did it prove to be in various ways
that it was kept in almost continuous use, either at Cambridge
or Arequipa, until 1923, when 53,754 photographs of the sky
had been made with it.
With the Bache telescope the spectrum investigations of
the Henry Draper Memorial were begun. By placing a large
prism over the object glass, stellar spectra of excellent quality
were obtained. The work of this instrument was later supple-
mented by that of various photographic telescopes of greater
size, notably the n-inch Draper and the i3-inch Boyden
refractors. From one to four objective prisms were used,
depending upon the brightness of the star. The length of
6 Amer. Journ. Sci., 18, 419, 1879.
Phil. Trans. Roy. Soc., p. 669, 1880; Proc. Amer. Acad., 19, 231, 1884.
120 ASTRONOMICAL PHOTOGRAPHY
the spectra thus obtained varied from i centimeter, or even less,
to 10 centimeters. Even in the spectra of the smallest scale,
the excellence of the definition permitted the classification
needed for the various lists and catalogues of the Henry Draper
Memorial. 7
Construction and Guiding of Astronomical Cameras.
Various investigations into the general principles of photo-
graphic processes, in their application to astronomy, have been
made by members of the Observatory. There is no essential
difference between the lenses used for portraiture and those
for astronomical work. Indeed, in the early days of photo-
graphy, very large lenses were employed by professional photo-
graphers to avoid excessively long sittings, because the plates
then obtainable were extremely slow. Such lenses were used
by the Pickerings in their early investigations with only such
regrinding as was necessary to produce the desired scale and tc
give good definition over a large field; some of the lenses needed
no change. Barnard and others also used similar equipment
with marked success.
The lenses first used were doublets, later employed in a much
enlarged form in the 24-inch Bruce telescope. For many
purposes a single achromatic combination corrected for the
photographic rays has been used, a form similar to the ordi-
nary visual telescope except in the corrections given to the lens,
Such was the instrument made by the Henry Brothers of Paris,
and employed in the formation of the Astrographic Catalogues
and Maps.
Good lenses became generally procurable, but there were
other problems. To obtain well defined photographs of a
moving object, such as the moon or a star, the telescope must be
carried forward by a suitable driving clock, or other apparatus :
which will follow the object in its motion: the chief requirement
is an arrangement by which the effect of the earth's rotation
is neutralized. The apparent motions of the sun, moon, and
7 Mem. Amer. Acad., n, 179, 1888.
THE PHOTOGRAPHIC IMAGE 121
stars all differ, and must all be provided for, unless extremely
short exposures are to be given.
The vast majority of the celestial photographs in the Harvard
collection have been obtained with instruments guided by
mechanical means, in many cases devised or improved by
Professor W. P. Gerrish. An adjustable control dock regulates
the motion of the telescope, so that it follows the apparent
motion of the stars with such precision that the resulting images
on a chart plate are nearly circular. With small and rigid
instruments, the control clock is all that is usually necessary.
For larger telescopes, however, the experiment becomes
correspondingly more difficult. Further mechanical devices
may be employed to advantage; but for instruments of great
size, personal guiding of the telescope becomes necessary in
order to obtain the best results. The image of a star, either in
the field of the telescope itself or of the "finder," is followed
visually and all irregularities of motion are promptly corrected
by the observer. W. H. Pickering made an early investigation
into some of the principles involved in celestial photography,
as an introduction to his study of the Orion Nebula. 8
The Photographic Image* An investigation of the forms
of images in stellar photography was begun by E. S. King in
1896. The form of an image is chiefly influenced by the rate
of the clock, refraction, the adjustment of the polar axis,
flexure, and any imperfection in form of the driving gears which
would introduce periodic irregularities in the motion of the
instrument. King showed that the usual supposition that a
star moves on sidereal time is incorrect. Even on the meridian
there is a deviation due to refraction. The instrument, too,
may be adjusted on the true pole with its axis parallel to the axis
of the earth, but, if it is adjusted by polar stars, its adjustment
is on the refracted pole. The real motion of the star is never
sidereal and rarely uniform. King made a careful determina-
tion of the corrections to dock rates which would allow for the
8 H. A., 32, Part i, 1895.
122 ASTRONOMICAL PHOTOGRAPHY
various irregularities caused by differential refraction, polar
adjustment, flexure, and the like, and his results have been
used in practice with much success. 9 A long, elaborate, and
important series of investigations, dealing with many of the
principles involved in photography, has also been carried on for
many years by King. The results obtained are referred to later
under the special problems concerned. 10
Photography has entered into all departments of observa-
tional astronomy, and in some of them, as in spectroscopy,
it has practically displaced visual observations. The great
advances of the last half century would have been impossible
without it. Most of the recent work of the Harvard Observa-
tory has been based on celestial photographs. The great
collection now housed at Cambridge contains some 300,000
photographs, which constitute a history of the sky for nearly
half a century. Even the early plates do not appear to have
suffered serious deterioration by lapse of time, and in many
respects they increase in value with age.
The dream of G. P. Bond of a time when photographs of stars
to the tenth magnitude might be obtained came true long ago,
not many years after his early death. Had he lived to old age,
he himself would have seen its fulfillment. Today stars to the
tenth magnitude can be photographed in a fraction of a second,
and with long exposures, stars many thousands of times
fainter, below the twentieth magnitude. One may well wonder
what the future will reveal.
9 H. A., 41, No. 6, 1902.
10 H. A., 59, 1912.
CHAPTER XI
STELLAR PHOTOMETRY, VISUAL AND PHOTOGRAPHIC
THE determination of the brightness of celestial objects
by photometric methods has occupied a prominent place in the
history of the Harvard Observatory. In preceding chapters
much has been said of researches concerning the brightness of
various members of the solar system, and what follows relates
chiefly to the photometry of the stars.
The Beginnings of Photometry. The desirability of
grouping the stars according to their brightness, or magnitude,
was recognized by ancient astronomers. The earliest record
of an attempt of this nature, which has come down to us, is
given in the Almagest of Ptolemy (Epoch, 138 A.D.). The
results there given, however, appear to have been derived
from the observations of Hipparchus (second century B.C.).
All the stars visible to the eye are divided in the Almagest
into six classes, called "magnitudes," the first group including
20 of the brightest stars, the sixth group or magnitude including
stars faintly visible, and the other groups, the intermediate
magnitudes. Ptolemy also used the terms " greater " and
"less" to indicate magnitudes brighter or fainter than the
average magnitude of a class, thus permitting more precise
estimates of the individual stars. The letters representing
these words have been replaced in modern times by decimals,
at first expressed to tenths, and later, with the perfection of
photometric methods, to hundredths, and even in some cases
to thousandths of a magnitude.
For many centuries the world accepted the astronomy of
Ptolemy with little or no attempt to question its accuracy.
In the tenth century, however, Sflfi made a valuable revision of
123
124 STELLAR PHOTOMETRY, VISUAL AND PHOTOGRAPHIC
the magnitudes in the Almagest, giving additional stars. In
the catalogue of Ulugh Beg (Epoch, 1437), the magnitudes of
S6fi are retained. The work of estimating the visual magni-
tudes of the stars was enormously extended in more recent
times by many observers, especially by Tycho Brahe, the
Herschels, Struve, Argelander in his Uranometria Nova and
with Schonfeld in the Bonn Durchmusterung, Houzeau, Heis,
and Gould and his associates in the Uranometria Argentina
and in the Cordoba Durchmusterung.
Peirce's Early Photometric Experiments. Photometric
determinations of magnitude that is measures with a pho-
tometer used visually made little advance until the closing
quarter of the nineteenth century. In 1871, when Charles
S. Peirce at the Harvard Observatory planned a series of
photometric observations of certain stars, the only photometric
observations known to him were those of Seidel, of Munich,
who had observed in all 208 stars during the years 1844 to 1860,
using a Steinheil photometer; and a few observations by Rosen
at Poulkova and by Zollner. Wolffs observations of 475
stars made at Bonn from 1869 to 1875 w ^^ a Zollner photometer
were not published until 1877. 1
In attempting to reform the existing scales of magnitudes
by the aid of instrumental photometry, Peirce decided that
they should be so adjusted that equal numerical differences
in magnitude would be represented by equal ratios in light.
Fortunately, by Fechner's psychophysical law, the ratio of
light between successive magnitudes already in use was approxi-
mately constant, although the results obtained by different
observers varied considerably even among the naked eye
stars. Peirce attempted to reduce all the discordant scales
of magnitudes of the various observers to one, and to render
his magnitudes accordant with it. He made no reference to
the scale proposed by Pogson, and later adopted by Pickering,
in which the magnitudes were obtained by the use of 0.400
1 H. A., 9, Chap. 4, 1878; 14, 329, 1884.
THE POLARIZING PHOTOMETER 125
is a divisor of the logarithmic ratios. Previously, values as low
is 0.350 and as high as 0.440 had been involved.
It is obvious that the work of Peirce during the years 1871
;o 1875 was f a pioneer nature. It was begun at the Observa-
;ory in Cambridge under the general direction of Joseph
iVinlock, at that time director, and was carried forward in
Washington and elsewhere. The observations were made with
i Zollner astrophotometer attached to a small portable tele-
;cope. In this form of photometer, an artificial star, produced
3y lamplight shining through a small hole, is brought into the
leld of the telescope. Its light is then reduced by means of
i Nicol prism to equal that of the star to be compared. A cap
vas placed over the lens to reduce the brightness of the stars
vhen necessary. With such an apparatus Peirce measured the
ight of 494 stars, in declination from 40 to 50, North. His
)lan was to obtain the magnitudes of all the stars in Argelander's
Jranometria, between the above limits, in order to furnish the
nagnitudes of stars which might be observed " at every altitude,
vith which to compare others in forming a new uranography."
The value of Peirce's work was much increased by his dis-
:ussion of the nature of light and the colors of many stars,
ind by his elaborate comparison of the magnitudes of stars
riven in the lists of Ptolemy, Stifi, Ulugh Beg, Tycho Brahe, the
Herschels, Seidel, and the Bonn Durchmusterung. 2
The Polarizing Photometer and the is-inch Telescope.
\t the beginning of 1877, when Edward C. Pickering
:>egan his duties as Director of the Observatory, the need
'or further systematic and extended photometry of the stars
ras urgent. The work already done, while valuable in throwing
ight on the nature of the problem, was distinctly preparatory,
md gave little material for the use of astronomers. It is true
:hat estimates of magnitudes had been made for several hundred
thousand stars in the various Durchmusterungeri and else-
where, but they were on no uniform scale.
*H. A.,9, 1878.
126 STELLAR PHOTOMETRY, VISUAL AND PHOTOGRAPHIC
For the naked eye stars, the estimated magnitudes were
fairly accordant, but the introduction of telescopes of greater
power brought fainter stars into the problem. Large dis-
cordances occurred in the estimates of the fainter Durch-
musterung stars, and for very faint stars the estimates by
different observers sometimes differed by several magnitudes,
chiefly because of the diversity of the scales employed.
As a physicist already interested in photometry, Pickering
at once became absorbed in this problem. In spite of the
few brief lists of stars which had been observed photometri-
cally, the subject needed to be approached independently and
placed on a permanent foundation. It was desirable that
the magnitudes of the lucid stars, well established by many
centuries of usage, should remain unchanged except for minor
corrections, and it was hoped that the system might be capable
of indefinite extension by the adoption of a uniform scale of
magnitudes which would command the approval of the astro-
nomical world. Uniformity was achieved by the adoption
of the scale proposed by Pogson, that the ratio of one magnitude
to the next should be fixed as the fifth root of 100, 2.512, or
more exactly, as the number whose logarithm is o.4. 3 This
ratio gives results in essential harmony with the estimates of
magnitudes of the brighter stars since the time of Ptolemy.
It is a natural outgrowth of the conclusion of Sir John Herschel,
about 1830, that a star of the first magnitude is one hundred
times brighter than one of the sixth magnitude. It was neces-
sary, also, to fix upon a zero point for the scale, and this was
done by bringing the magnitudes into general agreement with
the values given in the Uranometria Nova and the Bonn Durch-
musterung. These principles for the determination of stellar
magnitudes both for zero point and scale have been generally
accepted by astronomers of all countries.
Pickering's first photometric observations were made with
the large refractor, to which were attached various photometers
devised by himself. Most of these were polarizing photometers.
3 M. N. R. A. S., 17, 13, 1856; Radcliffe Obs., 15, 296, 1856.
THE HARVARD PHOTOMETRY AND ITS EXTENSIONS 127
Wedge photometers were also occasionally used, but Picker-
ing early decided that whenever possible it was better to avoid
the use of any instrument in which the images of the stars are
compared with that of an artificial star.
The photometer commonly used with the large refractor
had movable double-image prisms and a revolving Nicol
attached to a graduated circle. When two adjacent objects
were viewed in this instrument, two images of each were
formed by the double-image prism, either of which, by turning
the Nicol, could be made as faint as was desirable. Whatever
their relative light, the faint image of the brighter could be
reduced to equality with the bright image of the fainter object.
The true relative magnitudes of the two objects could then be
deduced from the angle through which the Nicol was turned.
With a photometer of this kind only adjacent objects can be
compared, such as the components of double stars, or the
satellites of planets. During the years 1877 to 1879, observa-
tions of many double stars were made by Pickering, assisted
by Searle and Upton. In many cases the difference in light
between the components of double stars was more than 10
magnitudes, and in a few cases, from 12 to 13 magnitudes.
Such objects are extremely difficult of precise observation with
any photometer, and the results are doubtless affected by
considerable errors. In publishing this work no magnitudes
of the stars were given, but only the differences in mag-
nitude between the components, using the Pogson scale;
no zero for the scale of magnitudes had at that time been
adopted. 4
The Harvard Photometry and Its Extensions. Soon
after he assumed the duties of director, Pickering began to
plan the extensive stellar photometric surveys which in later
years contributed so much to the advancement of astronomy.
Much experimentation was necessary before an instrument
suitable for rapid and precise measurements was ready. The
4 H. A., II, Part i, 1879.
128 STELLAR PHOTOMETRY, VISUAL AND PHOTOGRAPHIC
photometer, devised by Pickering and constructed by the
darks, was called a " Meridian Photometer." With a meridian
instrument, the stars may be observed in the most favorable
position and can be brought into the field of view and identified
with ease and rapidity. The observer remains at all times in
the same position as regards the eyepiece, the line of sight is
horizontal, and comparisons are made with other stars, not
with artificial standards.
The first meridian photometer was ready for use early in
1879. The lenses had a diameter of 1.6 inches and a focal
length of 32 inches. It was designed especially to obtain the
relative magnitudes of all stars, of the sixth magnitude and
brighter, readily visible at Cambridge. It consisted essentially
of a horizontal telescope pointing east or west, having twc
similar objectives and a single eyepiece. A right angled prism
was placed in front of each lens. One of these was adjusted
so as to bring into view the Pole Star, a. Ursae Minoris, which
could be kept in any desired position by small readjustments
in the position of the prism. The other prism could be turned
about the axis of the instrument so as to bring into view a
star of any declination when near its meridian passage. The
collimation could be altered somewhat to permit an extension
of the time of observation. The two pencils of light, one from
the Pole Star and the other from the star to be compared,
passed through a double-image prism, compensated by glass 3
which gave two pencils for each star. By varying the angle
of the prism and the glass, the ordinary image of one star was
made to coincide with the extraordinary image of the other
star, when by the revolution of a Nicol the images could be
equalized. Readings of an attached graduated circle were
made, from which the relative magnitudes of the two stars
could be derived.
With this instrument, from 1879 t 1882, 4260 stars north oi
declination 30 and of magnitude 6.2 and brighter were
observed by Pickering, assisted by Searle and Wendell. In this
early work all the stars were compared directly with the Pole
THE HARVARD PHOTOMETRY AND ITS EXTENSIONS 129
Star which was assumed to have the magnitude 2.0. The
magnitudes of the stars thus obtained were subject to three
corrections. The first was due to any difference in the images
formed by the two objectives and was derived from comparisons
of the Pole Star with itself, at the beginning, middle, and
end of each series. The second correction was for atmospheric
absorption. For the best determination of this correction
many observations and elaborate discussions were made. The
third correction was due to any error in the assumption that
the magnitude of the Pole Star is 2.0. This correction, being
constant, serves merely to fix the zero of the scale of magni-
tudes. Since it seemed desirable to have the magnitudes
accord in general with the estimated magnitudes of Argelander,
a correction of +0.27 magnitude was obtained by a comparison
of the corresponding magnitudes of 100 circumpolar stars
of about the fifth magnitude, which were common to the Bonn
Durchmusterung and Uranometria Nova, and to the Harvard
Photometry. These stars, whose magnitudes were determined
with special care, were taken as standards, and in all later
photometric work the final magnitudes were made to depend
on the mean magnitude of the circumpolar stars, so that any
variation in the light of the Pole Star, which was still used as
an intermediary, would have no effect on the results. Any other
star of suitable magnitude would be satisfactory, and X Ursae
Minoris and a Octantis have been so used. The correction
first used, +0.27, combined with the correction for absorption,
gave 2.15 as the magnitude of the Pole Star. A later mean
value derived from many observations is 2.12.
At the beginning of the photometric work, careful observa-
tions of various kinds were made to determine whether the
light of the Pole Star was constant, with the conclusion that
its light did not vary sensibly. Nevertheless, in 1911, Hertz-
sprung showed that it was a variable star of short period.
W. W. Campbell had previously discovered that it was a
spectroscopic binary. The range of variation, as determined
by different observers, is between 0.08 and 0.17 magnitude.
130 STELLAR PHOTOMETRY, VISUAL AND PHOTOGRAPHIC
This variation was probably too small for detection by the
methods in use in iSyp. 5
During the years 1882 to 1886, wedge photometers were
used with the 15 -inch telescope by Searle for the observation
of faint stars. The polarizing photometers were not suited to
this work. One of the wedges employed was made by Hilger of
London, under the supervision of Professor Pritchard, who
undertook to superintend the construction of a wedge photom-
eter as nearly as possible like the instruments in use at the
University Observatory of Oxford. The Harvard observations
were undertaken not only to extend the knowledge of the rela-
tive brightness of faint stars, but especially to determine the
relations of the scales of magnitude used by different observers.
In the photometers employed, a wedge of tinted glass, optically
compensated by cementing to it a similar wedge of clear glass in
a reverse position, is placed in the focal plane of the telescope.
This completed wedge carries an opaque bar or heavy line
parallel to the edge of the wedge. The interval between the
transit of a star across the bar and its disappearance in the
wedge is the observed quantity from which the brightness
of the star is deduced. Various difficulties and uncertainties,
which are thoroughly discussed, arise in the use of such a
wedge. The zero and scale were based on the photometric
results of the meridian photometers, which were already in use
before the completion of this work. The first observations
undertaken were of the faint stars in the Bond Zone from
+o5o' to +ioo'. The results were considered so satisfactory
that the work was extended to two narrow zones from +49so /
to +5ooo', and from +545o' to +55oo'. The object of the
latter observations was to furnish aid in the determination of the
relation of the Durchmusterung magnitudes of the fainter stars
to the Harvard photometric scale. 6
The catalogue of 4260 stars north of 30 (measured with
the first meridian photometer) which became known as the
6 H. A., 14, Part i, 1884; H. C. 174, 1912.
8 H. A., 13, Part 2, 1888.
THE HARVARD PHOTOMETRY AND ITS EXTENSIONS 131
" Harvard Photometry," was only the beginning of the photo-
metric surveys which Pickering had planned. These surveys
were designed to include much fainter stars, and to extend
over the whole sky. For this purpose a larger instrument
was necessary, and a new one was constructed on the same
general principles as the small meridian photometer. The
chief modification was in the use of mirrors instead of right
angled prisms to reflect the light of the stars into the objectives.
The lenses of the new instrument were four inches in diameter
and about five feet in focal length.
With this photometer stars to the ninth magnitude could be
observed readily, and even to the tenth magnitude under
especially favorable circumstances. As in the former work,
four comparisons or settings were made on each night, and the
observations were carried on for three or more nights. The
principal work at first undertaken with this instrument, and
carried out during the years 1882 to 1888, was the determination
of the magnitudes of a sufficient number of stars in the Bonn
Durchmusterung to serve as standards for a photometric
revision of that work. All the stars not called fainter than 9.0
in the Durchmusterung, in zones 20' in width, at intervals of 5,
were observed. The plan was extended to declination 20,
to include the observations of Schonfeld. The observations
were made by Pickering and Wendell; 20,982 separate objects
were observed in 1067 series. They included a few variable
stars, planets, and satellites. 7
A complete discussion of this work was made by Pickering,
who gave also a description of the instrument, an account
of the stars selected, the circumpolar standards, atmospheric
absorption, and the methods employed, as well as a comparison
of the results with other modern catalogues, and a reduction
of the Bonn Durchmusterung to the photometric scale. The
Harvard and Bonn scales coincide at the fourth and eighth
magnitudes. 8
7 H. A., 24, 1890.
8 H. A., 23, 1890, 1899.
132 STELLAR PHOTOMETRY, VISUAL AND PHOTOGRAPHIC
Many later investigations were undertaken with the 4-
inch meridian photometer. Perhaps the most important
of these was the extension of the Harvard Photometry to the
far southern stars, thus making it cover the whole sky. The
methods employed were similar to those already described;
<r Octantis, whose magnitude is 5.47, was used as the com-
parison star in all the observations, but the final magnitudes
of the measured stars were independent of the brightness of
the Pole Star. They were derived from the mean magnitude of
standard stars selected from the catalogue of the northern
Harvard Photometry. A number of these stars of known
magnitudes were measured in each series. The zero and scale,
therefore, should be the same as that of the northern catalogue.
Nearly 8000 stars were observed during the years 1889 to 1891.
The observations were all made by Solon I. Bailey. Prelimi-
nary reductions of the series were carried out in Peru and Chile
as soon as possible after the observations were made, but the
final reductions and the publication of the results were carried
out in Cambridge under the direction of Professor Pickering.
Before the establishment of the Boyden Station at Arequipa,
while various sites were being investigated, the photometer was
in use. Thus at different times observations were made at
" Mount Harvard/' Peru (near Chosica), latitude south about
12, altitude 6500 feet; at Arequipa, Peru, south i622 / , 8000
feet; and at Pampa Central, Chile, south 23 10', 4530 feet. 9
During the years 1891 to 1894, Pickering, using the 4-
inch meridian photometer, made a revision of the northern
Harvard Photometry. The original observations had been
made 10 years earlier with a smaller instrument, and a redeter-
mination of the magnitudes was desirable. Several hundred
additional stars were also observed. 10 The history and descrip-
tion of the photometer, the methods of observation and reduc-
tion, and other matters relating to the work of this instrument
during the years 1891 to 1898, were published later. 11
9 H. A., 34, 1895.
H. A., 44, Part i, 1899.
11 H. A., 44, Part 2, 1902.
THE HARVARD PHOTOMETRY AND ITS EXTENSIONS 133
From 1895 t 1898, Pickering used the 4-inch photometer
in forming a photometric Durchmusterung 12 of all stars of
magnitude 7.5 and brighter, north of declination 40. This
investigation was extended to the south pole during the years
1899 to 1900, by Bailey at Arequipa, 13 for all stars of magnitude
7.0, and brighter. During the formation of the northern
Durchmusterung, photometric observations of a large number
of variable stars and other miscellaneous objects were made
by Pickering. 14
By the year 1906, more than a million comparisons of nearly
fifty thousand stars had been made with the 2 -inch and the
4-inch photometers. Ua Some of the brighter stars had been
measured many times, and, because the resulting magnitudes
inevitably varied somewhat, some confusion prevailed as to
which determination should receive the preference. Pickering,
therefore, prepared a revision of the magnitudes of all the
brighter stars, by taking the mean values of all the determina-
tions given in the different Harvard catalogues. Equal
weights were given to each catalogue, independently of the num-
ber of observations concerned. The mean magnitudes thus
derived from all the measures made during the years 1879 to
1906, for stars of magnitude 6.5 and brighter, were published
in Harvard Annals, 50, 1908. This catalogue received the name
of the " Re vised Harvard Photometry," and became the stand-
ard reference work for the magnitudes of the brighter stars. An
extension of the same work to the fainter stars, measured in
general with the 4-inch photometer, was published in
Harvard Annals, 54, 1908, and gave the revised magnitudes
of 36,682 stars fainter than magnitude 6.5. Volumes 50 and
54 of the Harvard Annals really constitute a single work, giving
the best visual magnitudes at that time available. In Harvard
Annals, 50, was also given the class of spectrum, taken in
general from Harvard Annals, 27 and 28.
12 H. A., 45, 1901.
18 H. A., 46, Part i, 1903.
14 H. A., 46, Part 2, 1904.
14 *H. A., 14; 23; 24; 34; 44; 45; 46.
134 STELLAR PHOTOMETRY, VISUAL AND PHOTOGRAPHIC
Stars but little fainter than the ninth magnitude could
be observed with the 4-inch meridian photometer. The
further extension of visual photometry demanded the observa-
tion of much fainter stars, and Pickering proceeded to the
construction of a larger instrument, consisting of a 1 2-inch
horizontal telescope into which the light of the stars was
reflected from a rotating silvered glass mirror, inclined 45
to the axis of the instrument. Although the instrument
remained a meridian photometer, the other principles involved
in its construction were rejected, for the express purpose of
avoiding loss of light in polarization. An artificial star was
used for all the comparisons, and a wedge of shade glass to
reduce the light, instead of a polarizing apparatus. With
this instrument Pickering first extended his Durchmusterung
revisions to fainter stars. 15 A great number of observations
also were made of the fainter comparison stars for variables;
of the Bond Zone from o4o' to ioo'; of a sequence in the
Pleiades; of sequences of the stars in the various Standard
Regions, 30 square, into which he had divided the sky; and
in the Kapteyn Selected Areas. Observations were also made
of other special objects. 16 For many years Miss Florence
Cushman took an important part in the work of reduction and
preparation for publication of the photometric observations.
During many years important photometric observations
were made by Wendell, using the 1 5-inch telescope with polariz-
ing photometers devised by Pickering. Since with these
photometers only adjacent stars could be compared, the sources
of error due to differences in the condition of the sky at various
points were avoided. The observations by Wendell were made
with unusual care and skill, and the results are correspondingly
precise. The investigations carried on by him consisted
chiefly of observations of variable stars and of the fainter
comparison stars for variables. 17
15 H. A., 70, 1909.
" H. A., 74, 1913.
17 H. A., 69, Part i, 1909; Part 2, 1913.
PLATE XIV. THE 12-INCH POLAR TELESCOPE.
PHOTOGRAPHIC PHOTOMETRY 135
From 1885 to 1917, many minor photometric investigations
were made in Cambridge, Arequipa, and South Africa. 18
Pickering planned for several years to extend the Harvard
Photometry to still fainter stars by the use of the Common
6o-inch reflector. Much time was spent in adapting the
instrument to this work. The results were not satisfactory,
however, since the images of the stars were poor. Meanwhile,
the development and progress of photographic photometry, with
its greater possibilities, made a further extension of visual
photometry of small importance.
Photographic Photometry, One of the most striking
features in the development of modern astronomy is the part
played by photography. Its possibilities were early recognized.
As a result of pioneer experiments in stellar photography,
begun at the Harvard Observatory by Whipple and Black
in 1850, George P. Bond was able to state by 1857 that . . .
the intensity and size of the images, taken in connection with
the length of time during which the plate has been exposed,
measure the relative magnitudes of the stars. 19 Little or no
attention was given to this important line of research for many
years following, chiefly owing to lack of funds.
Preliminary experiments in celestial photography, including
photometry, were begun in 1882 by E. C. Pickering and
W. H. Pickering. A photographic lens of 2^ inches aperture
was used at first, and later one of eight inches. Among other
results, it was found that accordant relative magnitudes could
be obtained from stellar trails. 20
In 1885, under the direction of E. C. Pickering, the subject
was again taken up in a serious attempt to find the best methods
for the determination of photographic stellar magnitudes.
The instrument employed was an 8-inch Voigtlander photo-
graphic doublet, reground by the Clarks, of 44 inches focal
18 H. A., 18, Nos. i, 2, 3; 33, Nos. i, 10; 64; 72, Nos. 4, 5, 6, 7; 76, Nos. 9, 12;
80, Nos. 7, 13.
19 Letter of G. P. Bond to William Mitchell, July 6, 1857.
20 Mem. Amer. Acad., n, 179, 1886.
136 STELLAR PHOTOMETRY, VISUAL AND PHOTOGRAPHIC
length; so that the scale of the plates agreed with that of the
Bonn Atlas. The measures and computations were made by
Mrs. Fleming. It was pointed out that for such determinations
the images of the stars may be either in the form of points,
lines, or surfaces. When they are trails, a correction for
declination is necessary. Points and trails were utilized in
this work. Comparison scales were formed by successive
images of a star, having exposures of 3% 9% 27% 8i 8 , 243% and
729*. The ratio of three between exposures was found to
give images differing by approximately one magnitude. Scales
were also made by the use of different apertures. Photographic
magnitudes were found for 1009 stars within one degree of the
North Pole, 420 stars in the region of the Pleiades, and 1131
stars near the equator. The plates were all reduced to a
common scale, which was compared with that of the Harvard
Photometry. Various difficulties arose, partly owing to a
want of photometric magnitudes of the faint stars. Com-
parisons were also made with the scales of Wolf and MM.
Henry. 21
Whatever of interest and value the above results may have
had, they were in no sense final. For several years following,
many experiments and measures of photographs were made,
but, owing to the difficulties involved and the lack of any
absolute photographic scale of magnitudes, little progress was
made.
The determination of photographic magnitudes would
be simple except for the great number of variations which
occur in photographic processes. One method of measurement
is by the use of a glass scale, containing a succession of stellar
images of different intensities, made by one star with different
exposures, or by a number of stars with the same exposure,
or by the use of different apertures. Images of the stars
whose magnitudes are desired, including a suitable number of
standard stars of known magnitude, are then compared with
the scale images. The observations thus obtained form a
21 H. A., 18, No. 7, 1890.
. MEASURES OF PHOTOGRAPHIC MAGNITUDE 137
series from which the desired magnitudes can be derived. In
reality, however, many complications and difficulties enter,
and the reductions may become complex and the results doubt-
ful. The methods and difficulties were carefully discussed
by King, Miss Leavitt, and others in the various publications
referred to in this chapter.
King's "Absolute" Measures of Photographic Magni-
tude. Beginning about 1900, an important and independent
contribution to the determination of photographic magnitudes
on a uniform or absolute scale was made by Edward S. King.
Preliminary investigations regarding the action of photographic
plates had been undertaken as early as 1896. These dealt with
the advantages and difficulties of photographic processes
and the technique necessary in order to obtain reliable results. 22
The great power of photographic methods for the determination
of stellar magnitudes is to some extent balanced by a multitude
of difficulties which tend to introduce systematic as well as
accidental errors. King's first photometric research was the
determination of the photographic intensity of various sources
of light. The scale was that of the Harvard Photometry.
Apparatus suitable for the investigation was devised by King.
The absorption of the lens of the n-inch Draper telescope was
determined, and the way was opened for the successful extension
of photographic photometry. 23
After the application of his methods to the photometry
of the moon and planets, King undertook the determination of
the photographic magnitudes of the bright stars by means of
extra-focal images. Seven foci were used, and their relative
photometric values were determined. The exposure was 60
seconds in all cases. Polaris and other standard stars were
included in each series. To eliminate accidental errors,
observations of each star were made on five or more nights.
Magnitudes were obtained for 33 stars. In order tc minimize
28 H. A., 59, No. i, 1912.
**Ibid., No. 2.
138 STELLAR PHOTOMETRY, VISUAL AND PHOTOGRAPHIC
the errors involved in photographic processes, as far as possible,
the following rules were observed: that the light of all the
stars should be equalized; that the exposures should all be
of the same duration; that the stellar images to be compared
should be on one plate and developed simultaneously; and that
the measures should be repeated several times. 24 This investi-
gation was extended later to include 76 stars, in general of
magnitude 3.5 and brighter. In the catalogue of these stars,
in which their photographic and photometric magnitudes occur,
the class of spectrum, taken from Harvard Annals, 50, is also
given. The mean differences between the photometric and
photographic magnitudes of 109 stars, in relation to their
spectral classification, are given in a special table. The proof
of this definite relation constituted an advance of great impor-
tance. The zero of the scale adopted made the photometric
and photographic magnitudes equal for stars of Class A. It
was shown that the differences between the magnitudes varied
systematically from 0.40 for Class Oes to +1.68 for Class
M. These results were slightly modified later by the data
derived from a greater number of stars. They make it possible
to obtain the photographic magnitudes of all stars whose
photometric magnitude and spectral classification are known. 25
His investigation was later extended to include 153 stars.
In regard to his methods, King stated :
. . . that the photographic magnitudes of the 153 stars here given are
"absolute" magnitudes: that the scale, or the relation of star to star, is
independent of any other series or system of magnitudes, visual or photo-
graphic. All the data for determining these relations have been derived
from the plates used in this investigation. The only point of contact
with the photometric magnitudes of H. A., 50 has been the condition, that
the mean of the photographic magnitudes for stars of Class A should agree
with the photometric values.
In connection with his magnitude work, King discussed the
question of an absorbing medium in space, and deduced some
^., No. 4.
Ibid., No. 5.
THE NORTH POLAR SEQUENCE 139
ridence of its existence. 28 The subject was again considered
iter when much more extensive material was available. King
included that:
All the indications point to the presence of an absorbing medium in
>ace, or some factor which produces effects similar to absorption, by
aking the more distant stars redder. 27
i a still later consideration of the subject, King presented
le hypothesis that a local cloud of absorbing matter, extending
'om the sun to at least 100 light years, envelops our local star
uster. 28
King's photometry was later extended to include the bright
;ars of the southern sky and to include results obtained by the
se of different instruments. 29 He also, by means of photo-
raphs made with the 24-inch reflector, carried out his measures
) stars as faint as the eleventh magnitude. 30
Although the out-of-focus methods of King gave excellent
jsults, their extension to very faint stars would be difficult,
not impossible. The adoption of an absolute scale and zero
oint, by the international committee on magnitudes, provided
secure and permanent foundation for future work. The scale
as the same as that of the Harvard Visual Photometry,
here the ratio is 2.512, or the quantity whose logarithm is
4. The zero finally adopted makes the photometric and
hotographic magnitudes equal for stars of Class A, of magni-
ides from 5.5 to 6.5. 31
The North Polar Sequence. When Pickering, in 1906,
efinitely began on a large scale the determination of photo-
raphic magnitudes, he had already been experimenting for
bout 20 years on the subject, but had been delayed by the
iherent difficulties of the problem and the lack of an absolute
Ibid., No. 6.
27 H. A., 76, No. i, 1916.
28 H. C. 299, 1927.
29 H. A., 76, Nos. 5 and 6, 1915.
80 Ibid., No. 10.
81 A. N., 186, 40, 1910.
140 STELLAR PHOTOMETRY, VISUAL AND PHOTOGRAPHIC
scale. In 1907, he announced his plan for the formation of a
standard Polar sequence, to be used in extending the uniform
scale of photographic magnitudes to the whole sky. Work on
such a plan had already been in preparation for several years.
In this investigation Miss Henrietta S. Leavitt, by her unusual
ability, originality, and enthusiasm, became the leading figure,
and to her Pickering intrusted the execution of his plans.
The precise determination of the Polar Sequence was of primary
importance. Its value in the progress of photometry could
hardly be overestimated, for as soon as this sequence should
be definitely established and accepted by astronomers, its scale
of magnitudes could be transferred by photographic methods to
any region in the sky. This has now been done extensively.
The North Polar Sequence, as finally adopted, consisted
of 46 stars between the fourth and twenty first magnitudes.
An additional 29 stars were measured, as well as 21 faint stars,
comprising all that could be measured within 3' of the Pole on
plates made with the 6o-inch Mount Wilson reflector. This
made in all 96 stars. In the adopted sequence, all stars brighter
than magnitude 11.4 are of Class A, with the exception of one F
star; 12 of the additional stars referred to above, from magni-
tude 6.8 to 13.5, form a sequence of red stars. One of the chief
difficulties in the way of obtaining precise magnitudes on an
absolute scale is that due to color, which leads to variations in
magnitude depending on many factors, such as differences in the
lenses and mirrors, in photographic plates, and in developers.
The magnitudes of the 96 stars were investigated on 299
photographs taken with 13 different telescopes, with apertures
varying from 0.5 inch to 60 inches. For stars of such great
range in magnitude, telescopes of different size were necessary;
also, since the errors involved are often large, the variety of
photographs employed was expected to cause the errors to
balance one another more or less. Both refractors and reflectors
were used. A number of independent methods were used in
the hope of reducing systematic errors; for example, different
foci for out-of-focus images; Iceland spar to reduce the light
THE STANDARD REGIONS 141
by a computed amount; objective screens; varying apertures;
and different exposures. All these methods are subject to
large systematic errors, and different plates taken by the same
method under apparently similar conditions often give diverse
results, so that too much weight should not be assigned to the
results of a single investigation. In all cases, corrections must
be determined and applied as far as possible.
The color equation was found to vary for different instru-
ments, as was to be expected. Miss Leavitt recommended the
adoption of the following definition:
Photographic magnitudes coincide with photometric magnitudes on
the Harvard System for stars having spectra of Class Ao between the
magnitudes 5.5 and 6.5, and are fainter than the photometric magnitudes
by i. oo magnitude for stars having spectra of Class Ko between the same
limits.
The results given in the table of adopted magnitudes were
compared with the photographic magnitudes obtained at the
Gottingen, Yerkes, and Mount Wilson Observatories, by King
at Harvard, and by others. Later researches have shown that
some modifications in the magnitudes are necessary. 32
The term " absolute" magnitude was frequently used by Miss
Leavitt in her publications, and sometimes by other investiga-
tors of that period. As employed by them it simply meant the
finally accepted magnitude of a star on an absolute scale,
whether photometric or photographic. The absolute magni-
tude of a star in the usage of the present day is the apparent
magnitude the star would have at a distance of ten parsecs.
The Standard Regions. Recognizing the impossibility of
determining physical constants for all faint stars, Pickering,
as early as 1884, devised a plan for dividing the whole sky
into 48 equal regions. These became known as the " Harvard
Standard Regions." The plan, as developed later, involved a
study of all the bright stars in the regions, but for the fainter
82 H. A,, 71, No. 3, 1914; H. C. 108, 1906; 125, 1907; 150, 1909; 160, 1910; 170,
1912.
142 STELLAR PHOTOMETRY, VISUAL AND PHOTOGRAPHIC
stars, a single sequence for each region near the center. In
1905 the more extensive plan of Professor J. C. Kapteyn,
having 206 " Selected Areas/' seemed destined to supplant
the Standard Regions, but as much work had already been
done on them, Pickering decided to complete the original plan.
A sequence was therefore selected near the center of each
region, consisting in general of stars from the sixth or seventh
to the sixteenth or seventeenth magnitude. For the stars of
these sequences, the photometric magnitudes are given,
derived from Pickering's visual observations (extending to
about magnitude 13.0 for all stars as far south as declination
15) and from observations by Bailey for regions farther
south. Fainter stars were beyond the reach of the photometers
in use. The photographic magnitudes were determined by
Miss Leavitt; the classification of the spectra by Miss Cannon;
and the positions by Miss Walker. For the determination of
the photographic magnitudes, duplicate exposures were made
at first on the same plate, one of the Polar Sequence, and the
other of the sequence to be measured. Later, the plates were
made in series. The sequences in the Standard Regions at
declination +15 were used to extend the same scale of photo-
graphic magnitudes to regions too far south to be compared
directly with the Polar sequence. 33
Standards of Magnitude for the Astrographic Catalogue.
The International Committee on Photographic Magnitudes
recommended to the various observatories which took part
in the preparation of the Astrographic Map of the Sky
that the magnitudes of the stars concerned should be reduced
to the scale of the Polar sequence. It also recommended that
a single observatory should make a comparison for selected
parts of the sky. 3 " An offer from the Harvard Observatory to
carry out this suggestion was accepted, and the investigation
was undertaken by Miss Leavitt. Sequences of from 15
33 H. A., 71, No. 4, 1917-
84 Bui. du Com. Internal. Perm. Carte du Ciel, 6, 391, 1913.
KAPTEYN'S PLAN OF SELECTED AREAS 143
to 22 stars were selected near the centers of the overlapping
zones, and the photographic magnitudes were determined
by a comparison with the stars of the North Polar Sequence
by the methods already described. The results for the northern
zones were published first. They include 108 series, from
declination +4. 5 to +64. 5. 35
The prosecution of this work was interrupted by the death
of Miss Leavitt in 1921, but later it was carried forward by
Miss Walker, under the direction of Dr. Shapley. The addi-
tional sequences needed to complete the investigation for the
southern sky from declination 2. 5 to 64. 5 were 96 in
number. 36
Kapteyn's Plan of Selected Areas. A large and impor-
tant contribution to the determination of photographic magni-
tudes was made in connection with Kapteyn's Plan of Selected
Areas. For the execution of his scheme, Kapteyn was obliged
to depend on the cooperation of other observatories. Pickering
offered the resources of the Harvard Observatory to furnish
certain data necessary to the progress of the plan. But first
need was for charts of all the selected areas, 206 in number,
distributed over the whole sky. This necessity was met by
photographs of these areas. For the northern sky, plates
were made with the Metcalf 1 6-inch telescope, having exposures
of 6o m and i m , and showing stars to about the sixteenth magni-
tude. For the southern sky plates were made with the 24-inch
Bruce telescope, having exposures of 120, and showing stars to
about the seventeenth magnitude. Both instruments were
photographic doublets.
The Harvard Observatory also furnished photographic
magnitudes on the international scale of a sequence of stars
at the center of each area, to be used as standards. This
part of the work was carried out by Miss Leavitt. The
methods employed were essentially the same as in the case of
36 H. A., 85, No. i, 1919.
36 H. A., 85, No. 7, 1924; No. 8, 1926.
144 STELLAR PHOTOMETRY, VISUAL AND PHOTOGRAPHIC
the Harvard Standard Regions referred to above. Twelve
photographic plates were received from the makers in a sealed
box. These plates were exposed successively in the telescope
for exactly io m , the first, sixth, and twelfth on the North
Polar Sequence, and the remaining plates on the desired areas.
Harvard Standard Regions were also included. Southern
areas were photographed with the Standard Regions at +15.
The magnitudes of all the sequence stars were derived at
Cambridge and sent to Groningen. All other reductions
as well as the labor of publication were done under the direction
of Kapteyn. The photographic magnitudes in the Kapteyn
catalogues were determined from the estimated diameters of
the images of the stars, all of which rest on the magnitudes
determined at the Harvard Observatory for the stars of the
sequences. For very faint stars, important assistance was
rendered by Scares, of the Mount Wilson Observatory. The
northern Selected Areas were published first. 37 After the
death of Kapteyn in 1922, the extension of his Plan of Selected
Areas to the southern sky was carried forward by his successor,
Dr. P. J. van Rhijn. 38
Photovisual Photometry. The determination of photo-
metric and photographic magnitudes by no means exhausts
the subject of stellar photometry. A study of all the radiant
energy of the star is needed. The difficulties of even a visual
photometry have been many, and a perfect agreement among
different investigators is not to be expected, as is shown by a
comparison of the scales of the Harvard and Potsdam visual
photometries. 39 The chief factor in causing such diversity
is color, but even in the case of stars of the same color, no
absolute accordance can be expected with different observers
and instruments. The wide divergence between the photo-
graphic and photometric scales is also largely due to color,
37 H. A., 101, 1918.
38 H. A., 102, 1923; 103, 1924.
39 H. A., 64, No. 4, 1912.
PHOTOVISUAL PHOTOMETRY 145
and consequently, to the portion of the spectrum involved.
A complete photometry would include the star's radiations of
all wave lengths independently. Such a photometry may be
effected by some form of thermocouple, but such a method
could not be used for faint stars at present. Visual photometry
attempts to measure the amount of the radiation which gives
the sensation of light. Photographic photometry shows the
intensity of those radiations revealed by the ordinary photo-
graphic plate. The two differ widely in the spectral regions
concerned. In the Draper Catalogue magnitudes were given
derived from measures of the photographic intensity of the
spectrum near the line G. The magnitudes thus obtained
differ from other photographic magnitudes. 40
It was early suggested that the many advantages of photo-
graphic processes might be utilized in photometry by the
use of a suitable combination of color screens and plates,
the effect of which would be to yield a scale of magnitudes
comparable to visual magnitudes. Such magnitudes are
known as photovisual. In connection with her work on the
North Polar Sequence, Miss Leavitt obtained some photovisual
magnitudes by the use of isochromatic plates and yellow screens,
but the results then obtained were not on an independent and
absolute scale, and were only accepted as provisional. 41 King
has made some interesting investigations in this line. As
in other investigations, he employed the method of out-of-
focus images, using the 8-inch Draper and the lo-inch Metcalf
telescopes. Plates stained with erythrosine, or commercial
isochromatic plates, were employed, light reaching them
through an intensely yellow screen (dyed with Rapid Filter
Yellow) which cut off the blue end of the spectrum. Polaris
was photographed on each plate as a standard, and corrections
were made for its variation in light. The magnitudes of 24
stars were obtained in this manner. The results would, of
course, be altered numerically by changes in the screen or the
40 H. A., 27, 1890.
41 H. A., 71, 142,
146 STELLAR PHOTOMETRY, VISUAL AND PHOTOGRAPHIC
plates, but, as King points out, they constitute a standard
in themselves. 42
King later extended his study of photovisual magnitudes
to include 100 bright stars. The observations were all made
with the 8-inch Draper telescope. The same color screen was
used, with plates similar to those previously employed. There
are no large differences between the completed photovisual
magnitudes and the corresponding photometric magnitudes,
the mean difference for the 100 stars being 0.07 magnitude.
These differences, however, become less as the stars become
more red, implying that the photovisual standard is nearer
than the photometric to the red end of the spectrum. King's
method gives an independent determination of color index,
numerically somewhat larger than that derived from visual
photometry, but on a definite scale. 43
Miscellaneous Results. In addition to the visual and
photographic photometry already described, a great number
of magnitudes of stars have been determined in connection
with other problems. In the Henry Draper Catalogue of
stellar spectra, both photometric and photographic magnitudes
are given. The former, when not derived from Harvard
Annals, 50 and 54, are Bonn and Cordoba Durchmusterung
magnitudes reduced to the scale of the Harvard Photometry;
but for stars south of 62 the photometric magnitudes were
derived from the Cape Photographic Durchmusterung by the
application of corrections depending on the spectral class.
The photographic magnitudes were also obtained, in some
cases, indirectly from existing catalogues. 44 For the extensions
of the Henry Draper Catalogue only photographic magnitudes
are given. They are obtained through comparison with a Stand-
ard Region, a Selected Area, a sequence of the Astrographic
Map, a variable star sequence, or the North Polar Standards. 45
42 H. A., 81, No. 4, 1919.
43 H. A, 85, No. 3, 1923.
44 H. A., 91 to 99.
46 H. A., 100, No. i, 1925; No. 2, 1926; No. 3, 1927.
MISCELLANEOUS RESULTS 147
Photometric problems still form a large part of the program
of the Observatory. Two of the major researches now occupy-
ing much of the time of the Observatory are extensive surveys
of the Milky Way for the discovery and investigation of variable
stars, and a systematic determination of photographic magni-
tudes on a uniform scale. Another phase of photometry
that has been developed at Harvard during the past six years
is the spectrophotometric work to which more extended refer-
ence is made in the chapter devoted to spectroscopy.
CHAPTER XII
SPECTROSCOPY
THE spectroscope has been surpassed only by the telescope
in its influence on the development of astronomy. Without
its power of analysis, little would be known of the real nature
of sun or stars. Although Fraunhofer pointed out the presence
of dark lines in the solar and stellar spectra during the early
part of the nineteenth century, the significance of these lines
was not made clear until 1860 and later, largely through the
labors of Kirchhoff and Bunsen. It is not strange, therefore,
that little or no attention was given to the subject of spectro-
scopy at the Harvard Observatory during the administration
of the Bonds, 1839 to 1865. Winlock's chief interests, 1866 to
1875, also lay in other directions, although he made spectro-
scopic observations of the sun at times of total eclipse, as
described elsewhere.
Visual Spectroscopy. Astrophysical problems did not
become of primary importance in the programs of the Observa-
tory until 1877 when Edward C. Pickering, a physicist, became
director. Great advances in stellar spectroscopy were destined
to be made by photographic methods, but these were not
begun at the Harvard Observatory until 1882. Meanwhile,
by the use of a direct-vision spectroscope with the large refrac-
tor, and with other telescopes, rapid surveys were made of
large numbers of stars for the detection of objects having
peculiar spectra. A large list of such objects was published,
and it was pointed out that the long period variables could be
readily found by the peculiarities of their spectra. The results
obtained were interesting and valuable, but visual observations
soon gave way to photographic methods.
148
EARLY PHOTOGRAPHY OF SPECTRA 149
Early Photography of Spectra. The characteristic lines
of the solar spectrum had been photographed as early as 1842;
but although Huggins made experiments in 1863, in the hope
of obtaining photographic spectra of stars, no characteristic
spectral lines were shown on his plates. 1 Dr. Henry Draper,
an amateur astronomer of New York, was the first to obtain, in
1872, the photographic spectrum of a star showing clearly
the spectral lines. Dr. Draper's spectroscopic studies were
brought to an end by his death in 1882, As a memorial to
his life and work, Mrs, Draper, his widow, established a
department of stellar spectroscopy at the Harvard Observatory,
which she supported with large gifts during her life and gener-
ously endowed at her death. The investigations thus carried
forward under the direction of Mr. Pickering became known
as the Henry Draper Memorial. It was this generous
support, much needed at that time, which enabled Pickering
to carry out spectroscopic researches on an unprecedented
scale, especially the classification of the spectra of great numbers
of stars. The results of these investigations have been of
almost incalculable value in the development of modern
astronomy.
The pioneer experiments of Fraunhofer had been made with
an objective prism, and later Secchi had used it in his visual
observations of the spectra of about 4000 stars; previous to
1885 observers in general had made use of the slit spectroscope
in their attempts to photograph stellar spectra. Pickering
returned to the use of the objective prism for stellar work.
For spectroscopic observations of such an object as our sun
a slit spectroscope is required, but for stars, which appear as
points even in a telescope, no slit is necessary. The first
investigation of importance was undertaken with an 8-inch
photographic doublet, in front of which was placed a prism hav-
ing a dear aperture of 8 inches and a refracting angle of 13.
Such an apparatus gives on the plate at any instant a narrow
broken line, which can be spaced out into a surface, either by
1 Phil. Trans. Roy. Soc., 154, 428, 1864; Mem. Amer. Acad., n, 179, 1882.
150 SPECTROSCOPY
changing the rate of the driving clock, so that it differs by the
desired amount from the sidereal rate, or by a slow motion
of the plate itself. The resulting spectra were in general about
one centimeter in length and showed sufficient details to enable
the character and class of spectrum to be determined.
With the plates and methods at first employed, the spectra
of stars to about the eighth magnitude could be photographed
with an exposure of one hour, and to the sixth magnitude with
an exposure of five minutes. Later, much fainter stars were
reached with instruments of no greater size but with a prism
of smaller refracting angle. For detailed study of the bright
stars, the n-inch Draper refractor, of nearly 13 feet focal
length, and the 13 -inch refractor of 16 feet focal length were
used with one or several prisms, according to the magnitude
of the star. For a few of the brightest stars, spectra have been
obtained four inches in length, showing hundreds of lines.
Various other instruments have been used for special problems.
The objective prism offers many advantages over the slit
spectroscope but has certain disadvantages. Less light is
lost, where all the light is of the utmost importance. Also,
many spectra can be photographed at the same time and on
the same plate. On the other hand a comparison spectrum
is difficult to obtain. An absorbing medium of some nature was
early tested. Perhaps the best material yet found is neodym-
ium chloride, but the results are not entirely satisfactory.
Spectra obtained with the slit spectroscope, with the accom-
panying comparison spectra of known substances, have
undoubted advantages in the determination of wave lengths,
of the motions of stars in the line of sight, and in other ways.
The First Draper Catalogue. The first Harvard catalogue
of stellar spectra contained a classification of the spectra of
10,351 stars north of declination 25. Few stars brighter
than the sixth magnitude were omitted. The spectrum of
each star was in general photographed several times, in all
cases with the 8-inch doublet and objective prism. The cata-
THE FIRST DRAPER CATALOGUE 151
logue was called the Draper Catalogue of Stellar Spectra. 2
It seemed necessary at the beginning to make use of an empirical
classification. Especial attention was given at first to the
four spectral types of Secchi; but it soon became evident
that a much more detailed classification was needed, and the
letters of the alphabet were adopted. All stars showing the
same characteristics were grouped under the same letter.
To stars of Secchi's Type I were assigned the letters A to D;
to those of Type II, the letters E to L; to Type III, the letter
M ; and to Type IV, N. Nearly all, if not all, of these letters
are used in the Draper Catalogue, but a number of them
were rejected later. For example, the letter C was later given
up because an apparent duplicity in the lines which it repre-
sented was found to be due to the poor quality of the photo-
graphs concerned. Also, in certain cases, two groups were
formed where but one was needed. For example, stars really
of the same class were at first placed under E and G; but
E was later rejected since apparent differences between the
groups were shown to be in the photographs but not in the
stars. These omissions and changes in the order of certain
letters to correspond with the probable life history of the stars
caused the final arrangement of the letters to appear somewhat
grotesque. To change the letters once assigned to stellar
groups would cause confusion, however, and the order of the
alphabet is not important, since the letters simply serve as
symbols.
No subdivisions of the classes represented by the different
letters employed are given in this early Draper Catalogue.
In a few cases for the fainter stars an interrogation mark (?)
is used to indicate doubt, and even when it is not employed
occasional uncertainties exist, due principally to the inclusion
of stars too faint for exact classification on the plates then
available. The work of measurement and classification was
done by Mrs. W. P. Fleming under the direction of Mr. Picker-
ing. During the progress of the work it became evident that
H. A., 27, 1890.
1 52 SPECTROSCOPY
stars of the different classes do not fall into distinct groups, or
types, but tend to pass insensibly from one class into another.
In addition to the spectral class, the Draper Catalogue gives
photographic magnitudes; and, in Table II, the hydrogen
lines of shortest wave length visible, the intensity of the
Fraunhofer K line, 3934, and the presence or absence of the
F line, 4861. A discussion of the plates and methods used and
the results obtained in the Draper Catalogue was published
later. 3
Miss Maury's Pioneer Analyses of Spectra. Early in
the progress of the Henry Draper Memorial, Pickering planned
a study of the spectra of bright stars with as much detail as
the equipment of the Observatory would furnish. With the
n-inch and i3-inch telescopes, each star was usually photo-
graphed near the center of a plate, and the number of prisms
and the exposure depended upon the requirements in each
case. One or more additional spectra often appeared, however,
on the same plate. To Miss Antonia C. Maury was assigned
the discussion of the photographs made in Cambridge, including
all bright stars north of declination 30. The work was
begun in 1888 but not completed until 1895 or 1896. About
4800 photographs of 68 1 stars were examined, all made with
the n-inch telescope by the use of from one to four objective
prisms. This telescope was originally constructed for visual
observations by Dr. Draper, but had been fitted to photographic
work by the addition of a correcting lens. Pickering considered
it of primary importance that each observer should group
together all stars having similar spectra, without especial
consideration to theory which could better be discussed later.
Miss Maury preferred not to follow the classification of the
Draper Catalogue, finding it inadequate for her purpose,
and advanced a new and elaborate classification of her own.
Her nomenclature is logical, and, with some modifications
and extensions, might well have met the needs of astronomers
8 H. A., 26, Part i, 1891.
MISS MAURY'S PIONEER ANALYSES OF SPECTRA 153
had it been generally accepted. It is evident, however, that
one classification is better than several, and the international
acceptance provisionally of the revised Draper classification
makes it desirable to translate other systems into it. This is
simple, in the case of Miss Maury's work, as is well shown in
Table XV, in Harvard Annals, 28, page 145.
In order to determine the wave lengths of lines in stellar
spectra, the solar spectrum was photographed with the n-inch
telescope, using a 1 5-inch reflecting telescope as a collimator.
The stellar spectra obtained with four prisms could then be
compared directly with the solar spectrum, both being on the
same scale.
Miss Maury was provided with plates made by the use of
three or four prisms for the detailed study of the brighter stars,
but for purposes of classification she employed uniformly
plates made with one prism, which were more comparable.
The classification was made to depend on the appearance as
well as the position of the lines. Since great differences
occur in the density of the photographic spectra, and hence
in the appearance of the lines, a comparison of a considerable
number of photographs was often made before the classification
was decided.
It had already been shown that for the most part stellar
spectra could be arranged in a series, and that this series
probably corresponded to some plan of development. Miss
Maury was of the opinion that a simple series was inadequate
to represent all the peculiarities which were present, and that
it would be more satisfactory to assume the existence of collat-
eral series. These, called "divisions," were designated by
the letters a, b, and c, characterized by varying degrees of
haziness, width, and intensity of the lines. Miss Maury
divided the stars according to their spectra into 22 main groups,
and gave a detailed description of each group and its subdivi-
sions, and of typical stars. Translated into the nomenclature
of the Draper Catalogue, the 22 groups of Miss Maury fall
under the letters, B, AB, A, AF, F, FG, G, K, M, N, and O,
I 54 SPECTROSCOPY
a result which appears more in harmony with the later Draper
classification than the early Draper Catalogue. Miss Maury
gave tables showing the identification, distribution, and
intensities of the solar lines found in the stellar spectra of her
groups from VI to XVIII, corresponding in the Draper classi-
fication to B, A, F, G, K, and M. Elaborate notes and com-
ments on the spectra of the stars were given, which have
proved of much value to special students.
Miss Cannon and the Draper Classification. In the
furtherance of Pickering's plans, during the years 1891 to
1899, 5961 photographs of the spectra of 1122 southern stars
and a few northern stars were obtained at the Arequipa Station
of the Observatory. They were made with the i3-inch Boyden
telescope of 16 feet focal length, with the use of from one to
three prisms. The dispersion of these prisms is such that the
distance on the plates from He to H/3 is 2.24, 4.86, and 7.43
centimeters, for one, two, and three prisms, respectively.
The discussion of these plates was intrusted to Miss Annie J.
Cannon.
Miss Cannon found it convenient to adopt the notation
of the Draper Catalogue, to which had been applied some
modifications suggested by the experience of Professor Pickering
and Mrs. Fleming. Miss Cannon's method of procedure
was to place all the plates in large groups corresponding to
the classes B, A, and so forth. Second type stars were placed
under Group G, and a detailed study of these was first under-
taken, which resulted in various extensions and subdivisions.
This process was extended to all the classes. In course of time
all the classes and their subdivisions became so definitely
established and so clearly visualized by Miss Cannon, that
she needed only to glance at a photographic spectrum in order
to determine its proper classification.
In any such system the presence and appearance of certain
lines form the basis of the classification. Most important
to be considered are the well-known hydrogen series, nearly
MISS CANNON AND THE DRAPER CLASSIFICATION 155
iniversally present, extending from Ha to Hy; the rare but
nteresting series found by Pickering in the spectrum of f
3 uppis, first attributed to hydrogen and later to helium;
he " Orion" lines, largely due to helium, but also to other
dements; the solar or metallic lines; and, in comparatively
ew cases, bright lines of one kind or another. Miss Cannon
ound it inadvisable to adopt the "divisions" a, b, and c,
:onsidered necessary by Miss Maury, but instead prepared
laborate remarks regarding the appearance of the lines when-
ever needed.
As few changes have occurred in the Draper classification
ince the publication of this investigation by Miss Cannon,
i brief outline of its chief characteristics may well be given
tere. From B to M the Draper classification represents clearly
L single, continuous series. The vast majority of all stars
all into this series. For each letter employed, decimal sub-
livisions follow to indicate successive variations leading to
he next spectral class. For example, B, or Bo, is used to
epresent spectra in which some of the "Orion" lines are as
Qtense as the lines of hydrogen. Nine subdivisions, Bi to
*9, are provided and may be used leading to the next class, A.
These steps indicate gradual decreases in the intensity of the
'Orion" lines and increases in the intensity of the hydrogen
ines. When Ao is reached, the "Orion" lines are generally
ibsent, the hydrogen lines very intense, and the solar lines
aintly present. The main classes of the whole series, as
ised by Miss Cannon in this work, may be seen best in tabular
orm.
P. Gaseous nebulae. Only one example in the catalogue.
Q. Peculiar spectra with bright lines. Three examples.
O. Fifth type. Bright bands on a faint continuous background.
B. Orion lines and those of hydrogen almost equally intense.
A. Hydrogen lines very intense. Disappearance of helium and beginning of
solar lines.
F. Hydrogen lines still intense and many solar lines.
G. Solar type, spectrum closely resembling that of the sun.
K. Hydrogen lines less marked, K line intense.
M. Banded spectra.
156 SPECTROSCOPY
In general B and A correspond to Secchi's Type I, F is inter-
mediate between I and II, G is II, K is intermediate between
II and III, and M is III. The position of Class O in the series
evidently preceded that of Class B. The relation of P and Q
to the other classes was less evident, but since they appeared
to be more nearly related to O than to any of the others, they
were placed before O. The spectra of Class O are divided into
the subdivisions Oa, Ob, Oc, Od, Oe, and Oes. In Oes all
the lines are dark and the type of spectrum approaches the B
stars closely. A special description of each Md star is fur-
nished. A table is first given containing the spectra of the
1 1 22 stars in the order of the above classification, and another
table in which they appear in the order of right ascension.
Detailed notes cover the peculiarities of individual stars. 4
The classification of bright stars, northern by Miss Maury
and southern by Miss Cannon, was given in Harvard Annals,
28. In the work on the northern sky, many stars of magn'tude
4.0 to 5.0, and a few brighter than 4.0, were omitted: 1726
photographs of these stars were made later than 1904 with
the 1 1 -inch telescope and the use of one prism. The classifica-
tion of these stars was carried out by Miss Cannon, on the same
system, from O to M, as that of Harvard Annals, 28, Part 2.
Class N was added for stars like U Hydrae having a wide
absorption band near wave length 4738. This catalogue con-
sists of 1477 stars, and additional tables are given of stars having
special peculiarities. 5 A work similar to the preceding for the
extension of the spectral classification to fainter stars in the
southern sky was also done by Miss Cannon. It forms a supple-
ment to Harvard Annals, 28, Part 2, and contains 1688 stars. 6
The Henry Draper Catalogue. One of the largest and
most important investigations ever carried out at the Harvard
*H. A., 28, Part 2, 1901. For later modifications of the classification, pro-
posed by the Committee of the International Astronomical Union on Spectral
Classification, see Trans. Int. Astron. Union, x, 97, 1922.
B H. A., 56, No. 4, 1912.
Ibid., No. 5.
Ml
PLATE XV. TYPICAL STELLAR SPECTRA: Bo, c ORIONIS; B8,
RIGEL; Ao, SIRIUS; Fo, CANOPUS; Go, CAPELLA; Ko, ARCTURUS;
Mi, BETELGEUSE.
(Facing page 156)
THE HENRY DRAPER CATALOGUE 157
Observatory is the Henry Draper Catalogue of stellar spectra,
which fills nine volumes of the Annals. This great work had
its beginnings in the early Draper Catalogue of Harvard
Annals, 27, and in its extension to all the bright stars (H. A.,
28). Its execution was possible only by the mass of material
which had been accumulated through many years of photo-
graphic work with different telescopes and prisms, both at
Cambridge and Arequipa. It was the culmination of the life
efforts of Edward C. Pickering, and the center of his interests
during the closing years of his life.
All the classifications in the Henry Draper Catalogue were
made by Miss Cannon, whose long experience in spectroscopic
observations made her eminently fitted for the work. Also,
the fact that all the classification was done by one observer
brought a uniformity into the results which could hardly have
been expected if several observers had taken part.
The spectra of bright northern stars, which had been classified
by Miss Maury and published in Harvard Annals, 28, Part i,
were reclassified by Miss Cannon in order to bring them into
harmony with the remainder of the Henry Draper Catalogue.
The classification of additional northern stars to the fifth
magnitude was taken from Harvard Annals, 56, No. 4. For
all southern stars brighter than the sixth magnitude the
results already published by Miss Cannon in Harvard Annals,
28, Part 2, and in Harvard Annals, 56, No. 5, were used.
In all other cases new classifications were made. Miss Cannon
had several assistants for the laborious identification of all the
objects and for other details of the investigation. The classifi-
cation of the stars in the catalogue was begun in October, 1911,
and was practically finished by the end of September, 1915,
although a few stars were added later. The total number of
stars whose spectra are included in the catalogue is about
225,000. The instruments and methods have already been
described. The classification here used is the same, with a few
additions and modifications, as that in Harvard Annals, 28,
Part 2. The main series extends from P to M. Two classes,
158 SPECTROSCOPY
R and N, were added, characterized by carbon and cyanogen
bands. Class S was later adopted by the International
Astronomical Union to designate spectra of a peculiar type
consisting of bright and dark bands. The relation of Classes
R, N, and S to the main linear series is somewhat uncertain,
but they may represent branches from it. The term "Pec."
was used in rare cases for spectra whose characteristics did not
permit them to be assigned to any known class. "Con."
was used to represent spectra which appeared to be continuous.
Each of the volumes contains a full page frontispiece illustration.
The nine plates show spectra of the different classes and with
varying dispersions, giant and dwarf spectra of the same class,
and portraits of Henry Draper, Mrs. Draper, and Edward C.
Pickering. Mr. Pickering died on February 3, 1919, when only
three volumes had been published. Thereafter Miss Cannon
supervised the publication of the remaining six volumes and to
her is due the successful completion of the work. 7
The Henry Draper Extension. A discussion of the mate-
rial of the Henry Draper Catalogue revealed inequalities in
different parts of the sky. In general, owing to better condi-
tions at Arequipa, fainter stars were included in the southern
sky than in the northern. This difference amounted to a
magnitude, the catalogue as a whole being complete to about
the eighth magnitude for northern stars, and to the ninth
magnitude for southern stars.
To balance the survey somewhat, and especially to explore
interesting areas in the Milky Way, Shapley decided, in 1923,
upon an extension of the Henry Draper Catalogue. 8 He did
not plan a uniform extension, but a survey of those regions of
most importance in his studies of stellar distribution. It was
estimated that about a million unclassified spectra were
available on plates already included in the Harvard collection.
The first region selected for the Extension was one covered by a
7 H. A., 91 to 99, 1918 to 1924.
8 H. C. 278, 1925; H. A., 100, No. i, 1925.
DISCUSSIONS OF THE HENRY DRAPER CATALOGUE 159
plate made with the lo-inch Metcalf triplet, with small disper-
sion, 2.23 mm from H/3 to He, but of excellent definition. This
plate, covering an area of about 80 square degrees with a center
at 2o h , +37, in the star cloud in Cygnus, contained the spectra
of 4490 stars, of which 498 had been included in the Henry
Draper Catalogue and 3992 were added in the Extension.
The classification, as well as the determination of the photo-
graphic magnitudes, was made by Miss Cannon. In a dis-
cussion of the results of this Extension, Shapley is led to the
following conclusions, given here in a very condensed form:
i. The limiting magnitude for completeness is just below the
eleventh, although fainter stars are included. 2. The Henry
Draper Catalogue for this region is practically complete to
magnitude 8.5. 3. In both catalogues Class M stars are
classified half a magnitude fainter than those of earlier types.
4. No new stars of Class O were found, and none marked
"Pec." 5. The international scale of magnitudes was used,
and a correction found for the magnitudes in the Henry Draper
Catalogue. 6. There was good accordance with the Henry
Draper Catalogue, but M stars were placed a trifle later, and
other types a trifle earlier in the Extension. 7. Class K. stars
were relatively less numerous in the Extension.
Two other sections of the Extension have been carried forward
by Miss Cannon, one containing 3000 additional spectra, and
the other, 5000 spectra. 9
Discussions of the Henry Draper Catalogue. A large
number of investigations related to the work of the Henry
Draper Memorial have been carried out at the Observatory.
A volume of such studies was published in 1912, although
some of the numbers included had been in print for several
years. In his discussion of the early Draper Catalogue,
Pickering had made an investigation into the distribution of
stars of different spectral types, from which he concluded that
the Milky Way consists largely of stars of the first type, Classes
9 H. A., 100, Nos. 2, 3, 1927.
l6o SPECTROSCOPY
B and A. Later, a grouping of 32,197 spectra confirmed his
previous conclusions and also indicated that stars of the second
and third types were distributed nearly uniformly over the whole
sky. 10
Pickering also made a special study of B stars. Using the
early Draper Catalogue and all other data available at that
time he compiled a list of 803 stars of Class B, and made a
discussion of their distribution. He found that a large propor-
tion of these stars are in the constellations Orion and Argo,
a fourth of them being contained in a region having only one
fiftieth of the area of the whole sky. He reached the conclusion
that nearly all B stars are comparatively bright. His tabulated
results indicated that, while among stars brighter than magni-
tude 2.5 one out of four is a B star, among stars of the sixth
magnitude only one in twenty is of that class. He predicted
that few if any B stars would be found fainter than the seventh
or eighth magnitude. 11
More recently, Dr. Shapley, in association with Miss Cannon,
has made important contributions to this subject, using the
enormously increased data provided by the Henry Draper
Catalogue. Shapley and Miss Cannon show the relation between
spectral type and magnitude. 12 The results are well brought
out by the use of diagrams. A table giving the frequency of
spectral divisions for successive magnitude intervals leads to
striking results. The percentage of stars of classes A, F, K,
and M remains about the same for all magnitudes up to the
ninth. For B stars there is a marked decrease as the magnitude
increases, and for G stars, a still more marked increase. The
results differ somewhat from those obtained by Pickering, but
the material discussed was about twenty times as great and,
in some respects, of better quality, than that used by Pickering.
Later, Shapley and Miss Cannon called attention to the
existence and influence of the local system of stars, having its
10 H. A., 56, No. i, 1912.
11 Ibid., No. 2.
H. C. 226,1921.
DISCUSSIONS OF THE HENRY DRAPER CATALOGUE 161
quatorial plane inclined about 10 to that of the Galaxy.
The distribution of 2450 bright A stars was shown on an Aitoff
hart of equal area projection. The investigation appeared to
onfirm the existence of the local cluster, but left many problems
or further study. 13
Miss Leavitt discussed the relation of spectral class to
nagnitude in the Harvard Standard Regions. The problem
aised was: do stars on the whole grow redder with increasing
aintness? If so, is it due to a relative increase in the number of
ate type stars, or to some other cause, such as an absorbing
nedium? Miss Leavitt concluded that the stars taken alto-
;ether from the seventh to the eleventh magnitude appear
edder with increasing f aintness. 14
In a discussion of the distribution of stars of spectral class B,
Jhapley and Miss Cannon have shown that the fainter B stars,
o magnitude 8.25, are confined to a narrow belt along the
[alactic circle, the bright stars alone indicating the existence
f a local cluster not coincident with the Galaxy. Four dia-
;rams were given containing the positions of all such B stars
eferred to the galactic plane, for the groups, brighter than
;.26, 5.26 to 6.25, 6.26 to 7.25, 7.26 to 8.25, respectively. 15
Shapley also made a discussion of the spectral constitution of
he nearer parts of the Milky Way; 11,030 stars are included in
he discussion, which is well illustrated by diagrams. Many
nteresting conclusions are derived, including the following:
tars of Classes A and K predominate in the nearer parts of the
tfilky Way (100 to 500 parsecs), in so far as the stars of ordinary
atalogues are concerned; dwarf K stars in this region would
>e too faint to appear on the photographs; the results are
ciodified by various obscure areas and the great rift in the
tfilky Way; and, especially, a remarkable uniformity exists,
xcept in certain details, in the galactic distribution of all
pectral classes except M. 16
13 H. C. 229, 1922.
14 H. C. 230, 1921.
16 H. C. 239, 1922.
" H. C. 240, 1922.
162 SPECTROSCOPY
Somewhat later, Shapley and Miss Cannon discussed the
distribution of stars of Class M in the Henry Draper Catalogue,
Practically all such stars are giants. The following conclu-
sions were made, here given in a somewhat condensed form.
1. For stars of Class Mb, brighter than the eighth magnitude,
no galactic concentration is shown; but Ma stars are more
numerous by 30 per cent between latitudes 10 and +30.
2. For stars fainter than the eighth magnitude both Ma and
Mb stars are concentrated to the Galaxy. 3. The apparent
galactic concentration of Ma stars is based on insufficient data.
4. Variables of Class Md appear to be concentrated to galactic
latitude 20, but there is a marked asymmetry in longitude.
5. In the direction of Taurus, there is one half, and in the
opposite direction of Sagittarius, twice the average number of
variables. 6. The fainter stars of Classes Ma, Mb, and Me
show a marked preference for the region of Sagittarius.
7. There are 1500 giant M stars within 500 parsecs of the sun,
and at least 3000 within 800 parsecs. 17
Shapley continued his investigation by a study of the
"Spectral Class, Apparent Magnitude, and Galactic Position
for Stars of the Henry Draper Catalogue." Counts were made
of the stars in selected fields, each with an area of 100 square
degrees. The relation between numbers of B and M stars
and galactic latitude was represented by diagrams. Among
the results shown are the predominance of the A and K stars
in the Milky Way, and the lack of galactic concentration of F
and G stars brighter than magnitude 8.25 18
Dr. Shapley later gave his attention to the density of stars
in space, using data derived from the Henry Draper Catalogue,
and from current investigations of the average absolute magni-
tude of the spectral classes. The chief results are summarized
in the accompanying table, in which the first and second
columns give the spectral division and the spectral classes
within the division, and the third column, the average number of
17 H. C. 245, 1923-
M Ibid., 248.
DISCUSSION OF THE HENRY DRAPER CATALOGUE 163
stars brighter than visual magnitude 8.25 in 100 square degrees.
The fourth column gives the distance in parsecs throughout
which the stars of each type have been collected; they vary
considerably with type.
Spectral Surface Distance Space
Division Classes Number Limit Number
B Bo-B5 29.7 880 4 4
A B8-A3 96.9 340 250
F As-F2 18.7 140 680
G Fs-Go 26.0 70 7600
Giant K Gs-K.2 69.0 350 160
Giant M K$-Mc 17.5 430 22
Dr. Shapley and Miss Cannon comment on the tabulation :
The values in the last column are the numbers of stars in a million
cubic parsecs. On account of the amount of material involved in these
counts, it is not probable that local aggregations have seriously affected
the results. The tabulation does not take account of the Cepheids, the
giants of Class G, the abnormally faint A stars, nor the dwarf K and M
stars. Stars of these last two classes are probably much more numerous
per unit volume than dwarf stars of Class G. As a first approximation,
the giant G stars may be taken as one-half as numerous as the giants of
Class M.
Perhaps the most interesting deduction from these results is that for
every Class B star that is in the stage of development represented by the
Orion and Scorpius clusters, there are about five giant M stars and seven-
teen hundred dwarfs like our Sun. This conclusion should be of some
significance in considerations of stellar evolution. 19
Dr. Shapley and Miss Cannon have also made a summary
of the studies of stellar distribution previously carried out,
with important additions and conclusions. Diagrams were used
to illustrate the galactic distribution of the B stars, the con-
centration of stars of all classes toward the galactic circle, and
the apparent frequency of various spectral classes. The
distances of the stars and the number of stars in unit volume are
again analyzed. 20
19 H. B. 792, 1923.
80 Proc. Amer. Acad., 59, No. 9, 1924; H. Repr. No. 6, 1924.
1 64 SPECTROSCOPY
Miscellaneous Problems. During the development of the
Henry Draper Memorial, spectrum plates of the whole sky
were made with lenses of different sizes and objective prisms
of different angles. With a large lens and small dispersion
the spectra of stars as faint as the eleventh magnitude have been
made. Among the many thousands of spectra photographed,
a very large number of peculiar spectra were found by careful
examination of the photographs, and it is probable that few
permanent objects of this character escaped detection. By
means of bright lines or other spectral peculiarities a large
number of novae, variable stars, and other special objects
were discovered. The classification and discussion of these
objects were carried on chiefly by Mrs. Fleming, under the
direction of Pickering. After the death of Mrs. Fleming in
igiij the work was completed by Miss Cannon and others.
Since the distribution of such objects generally bears some
relation to the Milky Way, the catalogues containing them,
in addition to the right ascension and declination, furnish also
the galactic longitude and latitude. Separate tables are
given for novae, gaseous nebulae, fifth type stars, stars having
bright hydrogen lines, spectroscopic binaries, Algol and other
variables, stars of spectral class N, and other rare spectral
types. The work is illustrated with two plates giving examples
of spectra of the above types. 21
A classification of the spectra of double stars has been pro-
vided by Miss Cannon, who examined 745 such objects on the
Harvard plates. The class of spectrum is given either for the
two components together or for each separately. When
the distance between the components is less than 10", it is
difficult to classify the spectra of the components separately
on plates made with the objective prism. Special devices were
tried to minimize this difficulty. 22
The Draper spectral classification depends on photographs
made with the objective prism. At other observatories, for
21 H. A., 56, No. 6, 1912.
Ibid., No. 7.
THE SPECTROSCOPY OF NOVAE 165
the most part, the slit spectroscope has been used. Miss
Cannon made a comparison of the results obtained by the two
instruments. Spectrograms made with slit spectroscopes were
loaned to the Observatory by the Directors of the Yerkes, Lick,
and Allegheny Observatories. The number of plates was 20,
48, and 35, respectively. The stars were independently
classified by Miss Cannon on both kinds of plates, and though
there were some striking differences of detail, the resulting
classifications showed fairly satisfactory accordance. A few
differences as large as 10 spectral subdivisions, or a whole class,
occurred, but for 51 of the stars there was no difference. A
comparison was also made of the classifications made by
Kohlschiitter at Mount Wilson and Miss Cannon at Cambridge,
with equally good accordance. 23
The Spectroscopy of Novae. Spectral studies regarding
novae, or new stars, have received considerable attention at
Harvard. Early in the history of the Henry Draper Memorial
it was found by Mr. Pickering and Mrs. Fleming that on a
plate containing hundreds of spectra such objects could be
readily detected by their striking spectral peculiarities, espe-
cially the bright lines. Many novae were found in this way,
as well as many variable stars. Announcements and studies
of novae are found in various Circulars. 24 Miss Cannon made
detailed investigations regarding the peculiarities and changes
in the spectra of Nova Persei, No. 2, and Nova Aquilae, No. 3.
The second of these is of special interest, since the spectrum
could be studied through five periods in the history of the star:
i. Before the outburst on June 7, 1918, the spectrum probably
some division of Class A. 2. Rapid increase in brightness,
numerous dark lines. 3. Near maximum, immediately follow-
ing which the spectrum changed into the typical nova form
having broad, bright hydrogen lines accompanied by dark
lines; many changes during decrease in light. 4. Oscillatory
**Ibid., No. 8.
"H. C. 42, 1899; 56, 57, 1901; 176, 1912; 209, 1918; 289, 1925; 295, 1926.
1 66 SPECTROSCOPY
period with frequent changes in brightness and spectrum.
5. A slow and fairly uniform decrease in light, with the nebular
band 4363 the brightest portion of the spectrum. 25
Another interesting object of this class was Nova Pictoris,
discovered in 1925. A long series of spectrum plates of this
star was made at Arequipa from a study of which Davidovich
concluded that Nova Pictoris followed the normal development
of a new star, but that the spectral changes were unusually
slow. 26
Double Star Spectroscopy. For nearly two centuries
visual double stars have been observed by astronomers.
Several thousands are known, the majority of which are physical
doubles, or binary systems. The period of revolution of the
components of such doubles is long, from a few years to hun-
dreds of years. Since the development of the spectroscope,
a large number of spectroscopic binaries have been found.
Such stars appear single even in a large telescope, since the
components are too close to be separated visually, but with
the slit spectroscope the radial velocity is shown to be variable,
indicating that the star whose spectrum is observed is acted
upon by a second body. A comparison spectrum must be used
in the observation of such stars, a process which has been found
difficult with the objective prisms employed at the Harvard
Observatory. Certain dose binaries, however, have both
components bright and revolving in such a plane and with
such a velocity that the spectral lines appear on the plates
alternately single and double. When one component of the
system is approaching the observer, in its revolution about
the common center of gravity, and the other component is
receding, the corresponding lines of the two stars are separated;
at other times they are single. Pickering was the first to
discover a star of this sort, f Ursae Majoris, in 1889. Its
period, at first thought to be 52 days, was later shown by Vogel
25 H. A., 56, No. 3, 1912; 8x, No. 3, 1920.
* H. B. 823, 826, 835, 839, 1925.
SPECTROSCOPIC PARALLAXES 167
to be 20.5 days. Later in the same year Miss Maury found a
similar star, /3 Aurigae, with a period of about 4 days. A
third, p 1 Scorpii, was found at Arequipa in 1896, by Bailey,
having a period of a little less than 35 hours. A few other such
objects have since been found, but the number discovered
at this Observatory is small. 27 A discussion of a long series of
photographs, covering many years, of p l Scorpii and V Puppis
has been made by Miss Maury, who finds them to be among
the spectroscopic binaries having the highest radial velocity,
the mean amplitudes being, respectively, 480 and 604 km.
They are similar in having high velocity, low eccentricity,
small orbit, and great mass; ju 1 Scorpii is an eclipsing variable
of the ft Lyrae type, with small range. 28
Spectroscopic Parallaxes. The determination of the
distances of the stars presents one of the most difficult problems
in astronomy, and the method of spectroscopic parallaxes
renders powerful assistance. The first suggestion that a
relation exists between the intensity of certain spectral lines
and the absolute magnitude was probably made by Hertz-
sprung. 29 Nothing further appears to have been done about
it, however, until 1914, when Adams and Kohlschutter, of
Mount Wilson, developed the subject independently, carried
it forward systematically, and obtained definite results. The
presence of thousands of spectrum plates at the Harvard
Observatory promised great extensions of this line of research,
provided spectra obtained with the objective prisms were
suitable for the purpose. In 1916 Dr. Shapley, then at the
Mount Wilson Observatory, offered to investigate this matter,
and a number of photographs of various spectral classes were
sent to him by Pickering. These objective prism spectra
were found to be satisfactory. In 1921 Shapley, then Director
of the Harvard Observatory, in association with Lindblad,
27 H. C. ii, 14, i8g6; H. A., 28, 230, 1897.
28 H. A., 84, No. 6, 1920.
29 Zs. f . Wiss. Phot., 5, Part 3, 1907.
1 68 SPECTROSCOPY
who was also familiar with the recent Mount Wilson methods,
determined the absolute magnitudes and distances of 50 stars
of types Ko and K2 from a study of Harvard plates. In
general, the criteria employed at Mount Wilson were used,
giving most weight to the changes with absolute magnitude
of the line X 4215 of ionized strontium, but also using the
cyanogen bands, and the lines of hydrogen, calcium, and
manganese. 30 A little later Dr. and Mrs. Shapley determined
the distances of 87 bright stars of Class K. For stars common
to Harvard and Mount Wilson, the differences were satis-
factorily small. They reached the conclusion that, in addition
to the criteria already in use at Mount Wilson, several other
characteristics which had been found promised to extend the
usefulness of the Harvard photographs to fainter stars. 31 In
later publications Shapley has pointed out that, on account of
outstanding errors in existing photometric scales and in indi-
vidual estimates of brightness, the absolute magnitudes for
most classes of stars can be estimated as accurately as the
apparent magnitudes are known, and that, for stars fainter
than the eighth magnitude, the uncertainties in apparent
magnitudes make further refinements in absolute magnitudes
of little immediate value for many classes. A table of distances
based on the apparent magnitudes and spectral classes as
given in the Henry Draper Catalogue furnishes results fairly
satisfactory for ordinary statistical purposes. Such a table
of mean results for 105,529 stars of that catalogue is given.
Spectral parallaxes were also determined by independent
methods for several hundred southern stars. The results,
when compared with Mount Wilson, indicate a small systematic
difference. 32
Development of Spectrophotometry, In recent years
quantitative methods have invaded stellar spectroscopy, as
80 H. C. 228, 1921.
31 H. C. 232, IQ22.
82 H. C. 243, 246, 1923.
DEVELOPMENT OF SPECTROPHOTOMETRY 169
they invaded stellar photometry during the previous half
century. Much work at Harvard has been directed to the
establishment of stellar spectrophotometry during recent
years.
Detailed studies of physical conditions in the atmospheres
of stars, such as were undertaken by Miss Payne and her
associates in 1923, 33 showed at once that real progress must
depend upon accurate methods of measurement. The begin-
nings of Harvard spectrophotometry are to be found in
Shapley's note on the intensity of the hydrogen lines in the
spectrum of Vega, 34 derived by the same method that has
since been used in most of the Harvard investigations in
spectrophotometry.
The subject has been vigorously pursued at Harvard, espe-
cially by Miss Payne, 35 Hogg, 36 and Dunham, 37 and there
can be no doubt that observational stellar spectroscopy has
entered upon a new era. Theories that have hitherto ranked
as qualitative speculations can now be put to the test, and there
is every reason to believe that much of the current uncertainty
as to the conditions in the atmospheres of the stars is soon to
be dispelled.
33 H. C. 252, 256, 263, 1924; 287, 1925; 300, 1927; H. Mon. i, 1925.
34 H. B. 805, 1924.
86 H. C. 301, 302, 303, 304, 1927.
36 H. C. 301, 1927.
* H. B. 853, 1927-
CHAPTER XIII
VARIABLE STARS AND NOVAE
THE subject of variable stars has assumed an increasing
importance in astronomy. Not only do these stars contribute
to our better understanding of the nature of the sun, but
also they have recently been recognized as of great value
in the interpretation of cosmic problems. Interesting objects
on their own account, they appear to have completely escaped
detection by ancient astronomers, although several of them
are sufficiently bright to be observed with the naked eye.
Excluding novae, the existence of a variable star was probably
first recognized in 1639, by Holwarda in his observations of o
Ceti. This star had been seen by Fabricius in 1596, but he
probably regarded it as a nova.
Classification of Variable Stars. Little progress was
made in the discovery and observation of variable stars for
two centuries, until the subject was placed on a scientific basis
by the work of Argelander and Schonfeld. Argelander com-
piled a list of 1 8 stars supposed to be variable in 1844, and
undertook their observation. In 1854, Pogson published a
list of 53 known variables. In 1865, Schonfeld issued a
catalogue of 113 variable stars, and, in 1875, one of 165 stars.
This was the condition of the problem when the subject was
taken up at the Harvard Observatory under the direction of
Edward C. Pickering. Previous to his administration no
attention had been given to variable stars. In 1880 Pickering
published a paper on the dimensions of stars, with special
reference to binaries and variables of the Algol type; he dis-
cussed the characteristics of such binaries, determined the
elements of Algol (/3 Persei), and pointed out that the period was
170
AMATEUR OBSERVATIONS OF VARIABLES 171
subject to change. In this article he first proposed his division
of variable stars into five classes. His classification has received
long and wide acceptance and nothing essentially better has
yet been proposed, although various subdivisions are perhaps
desirable.
The system is essentially as follows: 1
1. Temporary, or new stars, Novae. Example, Tycho Brahe's star of 1572.
2. Long period variables, large range in variation. Example, o Ceti.
3. Irregular variables. Example, a Orionis.
4. Variables of short period, moderate range of variation. Example, 6 Cephei.
5. Variables of the Algol type. Example, /3 Persei, Algol.
Other communications speedily followed, discussing the nature
of variations in the light of stars, and the progress of variable
star observations. 2
Amateur Observations of Variables. Pickering early
recognized the desirability of enlisting amateur assistance
in the observation of variables. In 1882 he issued a bulletin
entitled "A Plan for Securing Observations of the Variable
Stars/' calling for volunteers. Mr. Pickering thought that the
subject would appeal strongly to educated women of leisure.
While women have been eminent as patrons of science, and as
professional astronomers, it seems rather surprising that among
the vast number of observations of variable stars which have
been contributed by scores of enthusiastic amateur observers,
the number of observations made by women is relatively very
small. Nearly all the active observers have been men, usually
very busy men. For several years Pickering's reports on the
progress of variable star observations were made through the
medium of the Proceedings of the American Academy, doubtless
from motives of economy.
During a trip to Europe in 1883, Pickering found two
unpublished catalogues of observations made by Sir William
Herschel, which he also discussed and published in the Pro-
1 Proc. Amer. Acad., 16, i, 1880.
*Ibid., p. 257; 370, 1881; H. A., 46, Chap. 9, 1904.
172 VARIABLE STARS AND NOVAE
ceedings. 3 Later, he published in the Annals an " Index to
Observations of Variable Stars/' designed to give information
on the subject for the whole period from 1840 to iSSy. 4
In 1888, Seth C. Chandler, an amateur astronomer, closely
associated for many years with the Harvard Observatory,
published his first catalogue of 225 variables, which was followed
in 1893 by a second catalogue containing 260 stars, and, in
1896, by a third catalogue of 393 stars. 5 These catalogues
show how rapid was the development of the subject.
The Harvard Catalogues of Variable Stars. Meanwhile,
at Harvard, much attention was given to variable stars. The
first provisional catalogue of variable stars published at the
Harvard Observatory, prepared by Miss Cannon, contained
1227 stars, including 509 in the globular clusters. 6 Miss
Cannon also prepared a second catalogue of variable stars,
including variables in clusters, published in 1907; it contained
1957 stars, and in addition 1791 variables had been found by
Miss Leavitt in the Magellanic Clouds, making in all 3748
known variables, 2909 of which had been found at the Harvard
Observatory. 7 By the end of 1927 the number of known
variables had passed 5000, of which 4106 had been found at
Harvard. This very large increase was due chiefly to the
introduction of photographic methods. A bibliography of
variable stars has long been maintained at the Observatory.
It was begun by W. M. Reed, in 1897, but since 1900 it has
been developed by Miss Cannon. It now contains about
50,000 entries providing information concerning known or
suspected variable stars.
The Naming of Variable Stars. The nomenclature adopted
for the designation of variables is of considerable importance.
3 Proc. Amer. Acad., 19, 269, 296, 1884; 20, 393, 1885; 21, 319, 1886; 22, 380,
1887.
4 H. A., 18, No. 8, 1890.
A. J., 8, 81, 1888; 13, 89, 1893; 16, 145, 1896.
6 H. A., 48, No. 3, 1903.
7 H. A., 55, Part x, 1907.
THE NAMING OF VARIABLE STARS 173
The system proposed by Argelander is, with some modifica-
tions, the one most widely employed. Argelander assigned
the letter R to the first variable found in a constella-
tion, as, for example, R Persei, the letter S to the second,
and so on to Z. Since his first list contained only 18 stars, this
plan seemed simple and satisfactory, but as the number of
variables increased it required extension. Additional designa-
tions were obtained by doubling the letters, RR to RZ, SS to SZ,
and so forth. In this way the number of names for a
constellation was raised to 54. This number, however,
later became insufficient, and further extensions were made
by the use of the letters, AA to AZ, BB to BZ, and so forth,
thus adding 280 more, and making in all 334. Even this
number has already become inadequate in Sagittarius and
Ophiuchus.
In his catalogues, Chandler introduced a method of designat-
ing a variable by giving it the number obtained by dividing
by 10 the number of seconds in the star's right ascension for
1900. This method is not used at the present time.
A different system, proposed by Pickering, was introduced
in the " Provisional Catalogue" of 1903. Each variable
was assigned the number, consisting of six figures, which
represents the approximate position of the star. The first
four figures gave the right ascension for 1900, expressed in
hours and minutes, and the last two figures, the declination
in degrees. Italics were used for southern stars. For example,
the approximate position of S Ursae Majoris for 1900 is i2 h
39 m .6 + 61 38', and the Pickering number is 123961. The
special advantage of this system is that the numbers are readily
remembered by the observer who uses them frequently and
give at once the position of the stars with sufficient precision
in most cases to enable approximate settings of the telescope
to be made. It was soon found, however, that the same
number occasionally occurred twice or more times, necessitating
the addition of the letters a, b, and so forth. This difficulty
will continually grow more serious. The system has been
174 VARIABLE STARS AND NOVAE
widely used by Harvard observers, and by the large number of
amateur observers associated with the Observatory, who have
found it well fitted for their observations. Both the Pickering
and Argelander designations have been given in most Harvard
publications.
Perhaps the best system ever proposed is that of Andre,
who suggested the use in all cases of the letter v to indicate
the variable, followed by a number representing the order of
discovery, and last by the name of the constellation. Thus,
v 25 Persei denotes the twenty fifth variable discovered in
the constellation Perseus. This system is capable of indefinite
extension, and has been recommended for general use in the
Report of the International Astronomical Union for 1925.
Visual Photometry of Variable Stars. Variable star
observations formed a part of the early work of the Harvard
Photometry. In forming the lists of stars for observation
with the first meridian photometer, in 1879, Pickering included
all variables contained in Schonfeld's second catalogue not
fainter than 6.5 at maximum. Later in the same research
he measured the brightness of the comparison stars for a number
of variables. 8
The same policy was pursued on a much larger scale in later
years by Pickering and other members and associates of the
Observatory. In connection with the photometric revision
of the Durchmusterung, Pickering and Wendell made photo-
metric measures of 166 variable stars during the years 1882 to
i888. 9 At about the same time, H. M. Parkhurst, an amateur
astronomer of high ability, began his contributions to the sub-
ject. He used the method of Argelander, estimating the
variable as equal to one of a sequence of comparison stars, or
between two comparison stars, one somewhat brighter, the
other somewhat fainter, estimating the intervals in grades.
From 1883 to 1891, Parkhurst made a large number of obser-
8 H. A., 14, 84, 401, 1884.
9 H. A., 24, 251, 1890.
STANDARD MAGNITUDES FOR OBSERVATIONS 175
vations of variables and of comparison stars. He also derived
light curves, and determined corrections due to moonlight,
to the use of shades, and so forth. 10
During the 20 years from 1892 to 1912, Wendell used the
i5-inch refractor with polarizing photometers for refined
observations of variable stars of different kinds, in addition
to his observations of double stars, asteroids, the satellites
of Jupiter, and other objects. His investigations were carried
out with extreme care and skill; and the photometers devised
by Pickering were capable of yielding results of much accuracy.
It is probable that Wendell's are the most precise observations
of variables ever made at the Harvard Observatory. His
work includes extended observations of variable stars of long
period, of Cepheid variables, and of variable stars of the Algol
type, and the light curves derived from them deserve the con-
fidence which they have received. 11 In particular, Russell
and Shapley used Wendell's work as a basis for the Princeton
studies of the orbits of eclipsing binaries.
Standard Magnitudes for Published Observations. Ref-
erence has already been made to the publication in the
Annals of some of Sir William HerscheFs variable star observa-
tions. Desiring to place before the astronomical public in a
convenient form the results of early observations of variables,
Pickering undertook the reduction and publication of a part
of the observations of Argelander, Schonfeld, and Schmidt.
The pioneer observations of Argelander, from 1838 to 1867,
had been published, but about 4000 later observations appeared
likely to remain unpublished, when Pickering undertook their
reduction and publication. A careful determination of the
value of Argelander's grade was made. It varied in different
years but the mean value was about 0.14 magnitude. The
comparison stars were measured with the meridian photometer,
with the exception of stars too faint, and the magnitude of the
i H. A., 29, No. 4, 1893-
11 H. A., 69, Part i, 1909; Part 2, 1913.
176 VARIABLE STARS AND NOVAE
variable for each observation was determined. A somewhat
similar investigation was made of Schonfeld's observations of
variables from 1853 to 1859, and of Schmidt's observations at
Athens from 1845 to ^79- These investigations made available
a large mass of material that would otherwise have remained
comparatively inaccessible. 12 Schonfeld's later observations,
made with great care between 1859 and his death in 1891,
lost for a time but afterwards found, were published in Germany.
In order to render these results available for the study of
periods and light curves, Pickering made a determination of
the magnitudes of the comparison stars on the photometric
scale. 13
Visual Observations at Harvard. A large proportion of
the Observatory staff, at one time or other, has made visual or
photographic observations of variable stars. Many determina-
tions of the brightness of variables and of their comparison
stars have been made with different photometers by Pickering
and others, beginning in 1896. The measurements included
variable stars of long period, of short period, and of the Algol
type. 14
Visual estimates of the magnitudes of variables were under-
taken on a large scale in 1889. An extended investigation
was made of 17 circumpolar stars, all north of declination +50,
selected because they were always above the horizon of Cam-
bridge and could therefore be observed at all seasons. The
plan included at least one observation a month of each variable,
so that the light curves would be known at minima as well as
at maxima. A sequence of comparison stars was chosen for
each variable, in general, although in one instance a sequence
was made to serve for two adjacent variables. A sequence
consisted of a group of stars, the successive members of which
differed in brightness by a third or a half of a magnitude,
12 H. A., 33, Nos. 4 to 6, 1900.
"H. A., 64, No. 3, 1912.
14 H. A., 46, Part 2, 1904.
VISUAL OBSERVATIONS AT HARVARD 177
the brightest star being somewhat brighter than the variable
at maximum, and the faintest, somewhat fainter than the
variable at minimum. Various observers took part in the
observations, but the greater part were made by Wendell,
Reed, and Miss Cannon at the Harvard Observatory, and by
F. E. Seagrave at his private observatory in Providence. The
work was prepared for publication by Wendell under Pickering's
direction. The observations were made during the years
1889 to 1899, and the results published with appropriate detail. 15
A similar investigation was undertaken of 58 variable stars
of long period in various parts of the sky visible at Cambridge.
Many observers took part, especially Wendell, Reed, Seagrave,
Waite, Campbell, and Miss Cannon. 16
In further extension of the visual investigations of variable
stars, Miss Cannon prepared a discussion of the maxima and
minima of all known variables of long period from data derived
from the published results of 38 observatories and scientific
journals. The information contained in these publications
was based on the labors of nearly 200 observers of different
countries, and included observations made from 1596 to 1909.
Although the investigation thus covered three centuries of
variable star problems, the vast majority of the observations
had been made within the last half century. Tables were
prepared by Miss Cannon, giving the dates of maxima and
minima and much other information for over 400 variables. 17
During the years 1902 to 1905, considerable progress in the
study of variable stars was made under Pickering's direction
at Cambridge, by the systematic observation and discussion
of 75 variables of long period. The methods used were similar
to those already described. A few observations were contrib-
uted by amateur astronomers, but the greater part of them
were made at the Observatory by Miss Cannon and Mr.
Campbell. When the variables were too faint at minimum
18 H. A., 37, Part i, 1900.
18 H. A., 37, Part 2, 1902.
17 H. A., 55, Part 2, 1909.
178 VARIABLE STARS AND NOVAE
to be observed with a small telescope, observations were made
by Wendell with the 1 5-inch refractor, or by Campbell with
the 24-inch reflector. 18 A large extension to the number of
sequences of comparison stars was also made at about the
same time. 19
Visual observation of variable stars has been carried on
until the present time, and has been greatly aided by the
contributions of other observatories and astronomers. The
results for the years 1906 to 1910, with a few unpublished
observations of preceding years, were discussed and prepared
for publication by Campbell, who himself made about half
of the 23,000 observations. The remaining observations
were made by 17 other members of the Observatory, and by 21
professional and amateur astronomers in other places. The
number of observations of variable stars published at Harvard
was thus increased to over 40,000. In the later work, the
estimates of magnitude of the variables were made directly
from the known magnitudes of the comparison stars, instead
of in grades, thus decreasing the work of reduction without
loss of accuracy. From 1906 to 1910, 328 variable stars were
observed, and 279 additional sequences of comparison stars
were selected and measured. 20
Similar investigations were continued under Campbell's
supervision during the years 1911 to 1916. The contributions
of amateur astronomers became of increasing importance
during this period through the enthusiastic cooperation of
the members of the American Association of Variable Star
Observers, to whom reference is made elsewhere. Assistance
was also given by the Variable Star Section of the British
Astronomical Association, the South African Association
for the Advancement of Science, and by Dr. Mitchell, Director
of the Leander McCormick Observatory. The published
results contain observations of 323 variable stars of long period
18 H. A., 57, Part i, 1907.
19 H. A., 57, Part 2, 1908.
20 H. A., 63, Part i, 1912; Part 2, 1913.
PHOTOGRAPHIC METHODS FOR VARIABLE STARS 179
during the years 1911 to 1916; and the maxima and minima
of 272 variables during the years 1900 to 1920. The observa-
tions of the members of the A. A. V. S. O. for 1911 were published
by the Observatory, but since that time they have appeared in
Popular Astronomy. 21 Extensions of the same investigations,
the discussion and publication of which are in progress, have
been carried on until the present time. Similar observations
are planned for the future, until sufficient data shall be accu-
mulated to make possible a definitive study of the behavior
of long period variables.
Photographic Methods for Variable Stars. Of more than
4000 variable stars discovered at the Harvard Observatory,
very few have been found visually. That method is slow and
difficult. Photographically, the case is very different. A series
of photographic charts of any region is easily made on dates
sufficiently separated. A comparison of these plates can then
be made under proper illumination in a comfortable room,
and the presence of any star of varying intensity may be
detected. Even easier methods have been developed. Early
in the work of the Henry Draper Memorial, plates made with
the telescope and objective prism were obtained which showed
hundreds of spectra, nearly all of which contained dark lines.
It was soon found by Pickering and Mrs. Fleming that special
objects having bright hydrogen lines of Class Md, usually
long period variables, could be picked up readily by a rapid
inspection of the plates. 210
Various other methods were derived for the detection of
variables, such as an automatic series of chart exposures on
the same plate, causing each star to appear as a succession of
black dots. In this way a Cepheid variable of short period
21 H. A., 79, Part i, 1918; Part 2, 1926.
110 In 1922, the notation Md was dropped by action of the Committee on
Spectral Classification of the International Astronomical Union ana a decimal
classification was adopted instead of small letters for subdivisions of M stars.
Trans. Int. Ast. Union, i, 97, 1922.)
180 VARIABLE STARS AND NOVAE
will often show distinct changes in the intensities of the images.
Another and more effective method is the superposition of a
positive of one date on a negative of another date. The
superposed light and dark images of an invariable star tend to
neutralize each other, while the images of variable stars show
a very different effect. Stereocomparators have also been
effectively employed. By these methods, in general, the great
additions have been made to the lists of variable stars in globular
clusters, the Magellanic Clouds, and the Milky Way, as well
as elsewhere in the sky.
After more than 3000 variables had been found at the Observ-
atory by various methods, in areas selected without a systematic
plan, a Durchmusterung of variable stars for the whole sky
was suggested in 1906. It was proposed to make the effort
international and to let it extend to as faint stars as possible.
Not meeting with much response from other institutions, the
Harvard Observatory undertook to carry out the plan by the
use of the Harvard Map of the Sky, which shows stars to
the tenth or eleventh magnitudes. 22 The method used was the
superposition of a positive on a negative, using five plates
made on different dates. The observations were made chiefly
by Miss Cannon, Miss Leavitt and Miss Leland. It is evident
that the greater the number of plates of a region examined
(up to a certain limit) the more variables will be found.
Through systematic investigation many new variables have
been found in different parts of the sky, and the results when
completed will enable a definitive study to be made of the
distribution of variable stars. While the total number of
variables which exists in a given area is not detected by an
examination of five plates, Pickering showed that the approxi-
mate total number can be derived from a study of the number
of variables already known and the rate of increase as the
number of plates examined becomes greater. For example,
Region 3 of the Harvard Map probably contains 42 variables
sufficiently bright to appear on the plates, of which 18 were
H. 0.71,1903.
VARIABLE STARS IN GLOBULAR CLUSTERS 181
previously known, 8 were added by the examination of five
plates, and about 16 remain to be detected. 23
The rapidly increasing collection of celestial photographs
early called attention to the possibility of a photographic
study of variable stars. The discovery of over 200 new
variables by means of their spectral peculiarities emphasized
the problem. The first need was for sequences of comparison
stars, which were accordingly selected by Mrs. Fleming for
222 variables. The determination of the photographic magni-
tudes presented insuperable difficulties at that time; photo-
graphic magnitudes on an absolute scale, later developed by
King, were not known. The magnitudes that were used were
reduced by means of visual magnitudes and were provisional in
nature, but gave empirical determinations of the relative
brightness of the stars. The magnitudes of 707 variables were
derived on all available plates; the observations, over 20,000
in number, extended over the years 1885 to 1905, and were
made by Mrs. Fleming and Misses Breslin and Leland. Aid
was also given by Misses Gill, Wells, and Stevens. 24
Variable Stars in Globular Clusters. The discovery that
many variable stars are present in certain globular clusters
was made by Bailey, at Arequipa, in 1895. Before that time
a few stars in or near such clusters had been announced as
variable, but little attention had been paid to them. While
comparing plates of the fine globular cluster o> Centauri made
on different dates, Bailey noted that several of the stars were
variable. This led him to undertake a systematic search in
various globular clusters on plates made by him with the
i3-inch refractor of 16 feet focal length. Fortunately, Messier
3 and Messier 5 were among the first clusters examined, and
both yielded surprising results. Of the stars visible to the
naked eye in the whole sky, not more than one or two per cent are
known to be variable. In the cluster Messier 3, an examination
23 H. C. 116, 1906; 127, 129, 130, 133-135, 1907; 137, uo, 142, 1908; 151, 1909;
152, 159, 162, 1910; 165, 1911; 179, 1913; 218, 1919.
24 H. A., 47, Part i, 1907; Part 2, 1912.
1 82 VARIABLE STARS AND NOVAE
of 900 stars revealed 132 variables, about i in 7, or 15 per c
of the stars examined. Approximately the same ratio *
maintained in this cluster, when, later, Shapley at Mo
Wilson increased the number of stars examined to 1000, \
the number of variables to 150.
Only a few clusters have large numbers of variables,
many clusters the percentage of variables is less than among
lucid stars. For example, in the fine cluster N. G. C. 6;
out of 600 stars examined only one variable was found, or
sixth of one per cent. Altogether, at that time, 509 varia
stars were found by an examination of 19,000 stars in 23 clust
something less than three per cent. The total number of knc
variables in clusters has since that time been much increa
by the observations of Misses Leavitt and Woods at the Harv
Observatory, by Shapley and his assistants at Mount Wils
and by others. Several hundred new variables have thus b
added, but it does not seem probable that the number will
greatly increased in the future, since the number of globt
clusters, at least within our present grasp, is limited, and ne*
all the important ones have already been examined.
The number of stars in some of the globular clusters is v
great. Photographs made at the Mount Wilson Observat
indicate the presence of at least 50,000 stars in Messier ;
faint globular cluster which to the naked eye appears 1
a hazy star of about the sixth magnitude. From theoret
and other considerations it appears probable that great m
bers of very faint stars are present, and that the whole num
may be half a million or more. At first it was thought that v
a sufficiently powerful equipment large numbers of varia]
might be found among the faint stars of these clusters. T
far, however, though carefully sought, no variable stars h
been found among the fainter stars in clusters. Variabi
evidently marks a certain epoch in a star's development i
occurs only there.
The name "cluster variables," suggested many years
by the writer, is generally applied to these variables. T
PLATE XVI. THE GLOBULAR CLUSTER o> CENTAURI.
(Facing page 183)
VARIABLE STARS IN GLOBULAR CLUSTERS 183
form a subdivision of the Cepheid group, belonging to Picker-
ing's Class IV, the short period variables. The periods of
cluster variables are between a fourth and three fourths of a
day, but the great majority have periods of about half a day,
or a little more. The median magnitude, however, of all
variables of this type in any cluster is uniform, whatever the
length of the period. This was noted early, and later confirmed
by Shapley. The range of variation in brightness is in general
from half a magnitude to a magnitude and a quarter. The light
changes are continuous, the increase to maximum extremely
rapid, the duration of maximum very brief, the decrease
relatively slow, with a continued slow decrease during the
minimum period. A detailed study by the writer of the
variables in w Centauri was the first published. 25 Studies of
the clusters Messier 3, 5, and 15 followed it. 26 These articles
contain the measurements and elements of the variables,
and the light curves; they are illustrated with marked photo-
graphic charts of all the variables. From an examination of
the globular cluster, N. G. C. 3201, Miss Woods found 56
variables, and from a similar examination of N. G. C. 6362,
15 variables. 27
A provisional catalogue of globular clusters was prepared
by Bailey in 1916; he concluded that 76 such clusters were
known at that time. A study of the distribution of the stars
in ten clusters was also given. 28 The number of known globular
clusters was later increased by Shapley, who has classified
95 such clusters, and in collaboration with Miss Sawyer, has
determined their photographic magnitudes. 29
The remarkable extension of our knowledge of the structure
and dimensions of the galactic system and the universe beyond,
which has resulted from Shapley's studies of the Cepheid vari-
ables in clusters and elsewhere, will be referred to in Chapter XV.
26 H. A., 38, 1902.
* H. A., 78, Part i, 1913; Part 2, 1917; Part 3, 1919.
27 H. C. 216, 217, 1919. See also H. C. 266 for an account of N. G. C. 6723.
28 H. A., 76, No. 4, 1916.
H. B. 848, 849, 1927.
1 84 VARIABLE STARS AND NOVAE
The Magellanic Clouds. As already stated, a persistent
search for variable stars was undertaken by different members
of the Observatory, as soon as the number of photographs
of the stars was sufficient for the purpose. The method most
employed was the superposition of a positive on several nega-
tives made on different dates. This search was most intensive
in certain selected areas, and the results obtained in different
regions varied greatly. The nebulous area in Orion, where
variables had been known or suspected for many years, was
examined by Miss Leavitt, who found 79 variables, many of
them new. An examination was also made of the nebulous
regions in Scorpio, Sagittarius, and Carina, the Trifid Nebula,
and other special regions, which altogether revealed several
hundred variables. It was not until 1905, however, when a
series of Bruce plates of the Magellanic Clouds, having long
exposures and showing very faint stars, was received from
Arequipa, that Miss Leavitt made the important discovery
that the Clouds contained variable stars in great numbers.
By 1908, the number known in the two clouds had reached
I777. 30 In publishing the positions of the variables, rectangular
coordinates were given in preference to right ascensions and
declinations, because the labor involved in their preparation is
less, and because their utility for identification is greater. For
the safe identification of closely massed stars, however, a
marked photograph is the best aid. Miss Leavitt gave the
periods of 16 variables in the Small Cloud, using a provisional
scale of magnitudes. With the adoption of a standard scale of
magnitudes for the stars of the North Polar Sequence, and with
the methods employed for its extension to all parts of the sky,
the subject was again taken up, and improved light curves and
periods were obtained for 25 variables in the Small Magellanic
Cloud. The periods of these 25 stars are from 1^.3 to 127^.0,
but 22 of them are less than 17 days. The variables are
of the Cepheid type in nearly all cases. The light curves
resemble those of the cluster variables.
80 H. A., 60, No. 4, 1908; H. C. 78, 79, 82, 90, 91, 1904; 96, 1905.
THE NOVAE 185
The Period-luminosity Curve. Probably the most impor-
tant result of the investigation of the Magellanic Clouds
was the discovery of the so-called "period-luminosity law/'
which Miss Leavitt found to hold for the 25 variables which
she discussed, with only moderate irregularities. By plotting
the periods as abscissae, and the measured magnitudes as
ordinates, and drawing a smooth curve through the observa-
tions, a relation between the two quantities is clearly shown:
the fainter the star the shorter the period. When the abscissae
were represented by the logarithms of the periods, the resulting
curve was sensibly a straight line. Since the variables are
evidently all members of the Cloud, and hence all at approxi-
mately the same distance, what is true for the apparent magni-
tudes must be true for the absolute magnitudes, and the
law if it is a law thus established becomes of great impor-
tance, and capable of wide extension. Shapley has shown,
however, that in the case of the Small Cloud, the depth, or
diameter of the cloud in the line of sight, is sufficient to produce
a dispersion in magnitude of o m .i4. The number of variables
included in Miss Leavitt's discussion was unfortunately rather
small, but the data have been much increased since that
time, especially by the studies of Shapley, whose work on the
Magellanic Clouds, and the application of the period-luminosity
curve to the determination of celestial distances, will be
referred to later. 31
The Novae. Novae form the first group in Pickering's
classification of variable stars. The term " temporary star"
is preferred by some writers to "nova," as undoubtedly more
exact. The word "nova," however, is older, briefer, and more
convenient, and, with suitable interpretation, may well be
retained. The sudden enormous increase of light, while in
no sense a creation, must mark some catastrophic event in the
life history of the star. Usually but one such outburst is
known for a particular nova.
81 H. C. 173,
1 86 VARIABLE STARS AND NOVAE
Considerable attention has been paid to new stars at the
Harvard Observatory. The first Harvard Circular, issued on
October 30, 1895, contained the announcement of a nova in
Carina, discovered by Mrs. Fleming from its characteristic
spectrum shown on a plate made in the preceding April. A
later plate revealed a marked change in the spectrum. An
examination was then made of all available chart plates of the
region, from which it was shown that the star had been invisible,
up to March 5, on plates showing stars as faint as the fourteenth
magnitude. On April 8 it was of the eighth magnitude, and on
July i of the eleventh magnitude. 32 A similar examination was
made in many other cases. At that time only 12 well-authenti-
cated novae were known, and today the number is only about
70, if those in spiral nebulae are excluded. When a nova was
announced, not only were old plates examined but new chart
and spectrum plates were made and repeated as long as the
object remained accessible.
Observations of Anderson's new star of 1901, Nova Persei,
No. 2, were made from February 22 onward, and an especially
good record was obtained of the striking spectral changes
which occur at or near maximum. In this case the nova rose
nearly to the magnitude zero. 33 An elaborate study of the light
changes was made by Campbell, 34 and later a similar study of
the light curves of Nova Geminorum, No. 2, 35 and Nova
Aquila, No. 3. Miss Cannon made a very complete study of
the spectral characteristics and changes for Nova Persei, No. 2,
with detailed lists of the lines observable at different times. 36
No observable star occupied the position of Nova Persei, No. 2,
previous to the outburst in 1901, but in other cases the nova
had been present as a faint star. Such a star was Nova Aquilae
No. 3. This object is shown on photographs of the region
in the Harvard collection made in the 30 years from 1888 to
32 H.C. i, 1895.
" H. C. 56, 57, 59, 1901.
34 H. A., 48, No. 2, 1903.
36 H. A., 76, No. u, 1915; 8r, No. 2.
34 H. A., 56, No. 3, I9I2 .
THE NOVAE
187
1918, during which time it was of about magnitude 10.5,
with various fluctuations in brightness. In June, 1918, it rose
j- o <Mf>frm*pf^coo>o
H?
to nearly the magnitude zero. Its early spectrum was approxi-
mately Class A, and its spectral changes were carefully followed
1 88 VARIABLE STARS AND NOVAE
at the Observatory. 37 A very complete and interesting record
was secured of Nova Geminorum, No. 2, discovered by Enebo
on March 12, 1912, showing clearly the successive changes
in the spectrum, from one having absorption lines similar to
a Canis Minoris to the typical bright line spectrum of novae. 38
Davidovich made a study of the spectrum and luminosity of
Nova Pictoris 1925.4, in which he determined the absolute
magnitude. He reached the conclusion that the increase of
light was probably produced by an expansion of the star, that
is, by an increase in the size of the luminous surface rather
than of its intensity. 39
During the years 1919 to 1921, a systematic photographic
search of the Milky Way, where practically all novae appear,
was undertaken for the discovery of novae and especially for
a study of their distribution and frequency. The observa-
tions were made chiefly by Misses Woods and Mackie, who, as a
result of their search, discovered 8 novae, in addition to finding
6 novae which were already known. During this investigation
1049 pairs of plates were compared. Owing to the brief dura-
tion of maximum of a typical nova and to difficulties inherent
in such observations, it is probable that such an examination
would disclose all novae of the fifth magnitude, or brighter,
at maximum, and a constantly decreasing proportion as the
magnitude was fainter down to the ninth magnitude. None
fainter than the ninth magnitude would be found. From the
results actually obtained it appears probable that, on the
average, one or possibly two novae of the sixth magnitude, or
brighter, at maximum, appear in the sky yearly and perhaps
ten, or possibly twice that number, of the ninth magnitude,
or brighter. Probably no nova as bright as the third or fourth
magnitude now escapes detection, but very few of the faint
novae that occur are ever observed. 40
37 H. C. 208, 1918.
38 H. C. 176, 1912.
39 H. C. 295, 1926.
> Pop. Astr., 29, 554, 1921.
THE AMATEUR'S CONTRIBUTION 189
The Amateur's Contribution; the A. A. V. S. O. The
American Association of Variable Star Observers, although
not a part of the Harvard Observatory nor officially under its
supervision, has had, nevertheless, such intimate relationship
with the Observatory, and has contributed so much to our
knowledge of variable stars, that some reference here to its
activities seems fitting. Work preparatory to such an associa-
tion was in progress for many years; as early as 1882 Edward C.
Pickering called attention to the opportunities for amateur
3bservers of variable stars. A special section was given to
variable stars in his Annual Report, beginning in 1905. Already
several professional and amateur observers were sending their
observations to the Harvard Observatory for discussion and
publication. The number increased each year until the
foundation of the A. A. V. S. O. in 1911. In the August number
3f Popular Astronomy for that year, the editor, Professor H. C.
Wilson, suggested the formation of an astronomical society
for the observation of variables, similar to the Variable Star
Section of the British Astronomical Association. This plan was
promptly approved by the volunteer observers already at
ivork.
Mr. William Tyler Olcott, a well known writer of astronom-
cal books and an assiduous observer, undertook its direction.
His rare ability, enthusiasm, and good fellowship brought suc-
:ess to the undertaking. Popular Astronomy offered to publish
;he observations free of expense to the members. Indispensable
lid was given by the Harvard Observatory in the way of
}hotographic charts of the variables and directions for observa-
ion. Most important of all, Pickering inspired the members
vith his own enthusiasm. Various professional astronomers
oined the Association, but by far the greater number were
imateurs. Men of all ranks in life became members.
Extremely active and helpful was Mr. David B. Pickering, a
successful business man and an equally successful watcher of
,he stars. One of the most interesting members was Mr. C. Y.
McAteer, an elderly locomotive engineer, who after long runs
i go
VARIABLE STARS AND NOVAE
tfi
W rn u
jjse
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*s ( i
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' Kii
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^ o tj n
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IPll
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|g|S.2
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u .a .2 J8
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n H P H-)
THE AMATEUR'S CONTRIBUTION 191
on his railway train, was never too weary to observe the stars.
For many years, Mr. Leon Campbell has been most efficient in
maintaining the relations between the Association and the
Observatory, and in increasing the number and quality of the
observations. The headquarters of the Association have always
been at the Observatory, where the annual reunions are held.
The Association has a collection of over a thousand astronomical
lantern slides for the use of members who wish to give illustrated
talks on astronomy, it possesses a library of about a thousand
volumes and pamphlets, and owns several telescopes, which are
loaned to active observers who do not possess suitable equipment.
From a group of seven observers at the beginning in 191 1, the
Association has grown to seventy five observers in 1927. During
the intervening years the members have made nearly 250,000
observations. About 500 variables have recently been under
observation, and 20,000 dates of maximum and minimum
have been derived. The observations have been published in
Popular Astronomy, but some discussion of them has been made
by Campbell at the Observatory, who used them to great
advantage in his investigation, A Tentative Classification of
Long Period Variables. 41 The Association has observers in
Argentina, Australia, Canada, England, France, Germany,
India, Italy, Japan, Russia, and South Africa, in addition to
the United States. The members are so well distributed
around the earth that observations can be maintained almost
continuously.
41 H. Repr. 21, 1920.
CHAPTER XIV
CLUSTERS AND NEBULAE
STAR clusters and nebulae are important and conspicuous
features of the Milky Way star fields. Perhaps on account of
their frequent proximity they were long classed together, and
the two names are even now rather loosely used to describe them;
for many so-called " nebulae" are really clusters of stars, and
clusters are occasionally involved in nebulosity. The subdivi-
sions, however, will be useful for general purposes, and are
retained in the discussion of researches that have been carried on
at the Harvard Observatory.
Stellar Clusters. Attempts to represent dense star clusters
by drawings, before the introduction of photography, were
made by Trouvelot. Two such drawings of the globular
clusters N. G. C. 6205 and 6341, in Hercules, are shown among
the illustrations in the Annals. 1 Clusters can be well and
accurately represented only by photographic plates made with a
telescope of rather large size. In 1888 the Observatory acquired
a suitable instrument which, after some trials at Cambridge,
was set up on Mount Wilson in 1889. ^ was an achromatic
refractor of 13 inches aperture with a focal length of 16 feet.
It could be used either visually or photographically and gave
excellent definition in either case. On Mount Wilson many
photographs of clusters were made by King and Black; later
the telescope was in use at Arequipa, where the investigation
was continued on a larger scale.
An early attempt to gain some information in regard to
the distribution of stars in the globular cluster w Centauri
was made by Mr. and Mrs. Bailey at Arequipa, in 1893. A
reticle composed of 400 squares, each 90" on a side, was placed
1 H. A., 8, Part 2, 1876.
192
STELLAR CLUSTERS 193
over the image of the cluster and the number of stars was
counted in each square. The number of stars photographed 2
in one fourth of a square degree, with an exposure of two hours,
was 6389.
The distribution of the stars in several clusters was later
investigated by Pickering and Mrs. Fleming, who also made
some observations of positions, brightness, and class of spectrum.
In general, the positions were given in rectangular coordinates,
expressed to tenths of a second of arc. 3
A catalogue of 263 bright clusters and nebulae was compiled
by Bailey in 1908, constituting a uniform Durchmusterung
of such objects for the whole sky. Photographs of one hour
exposure made with Cooke lenses of one inch aperture and
showing stars to the eleventh magnitude were examined; all
clusters and nebulae visible on such plates were included in
the catalogue, and no others. The descriptions of the objects
were made in general from an examination of Bruce plates of
one hour exposure. 4 Various typical examples are illustrated,
all on the scale, i' = i mm. A somewhat similar study was
made of the globular clusters, but all clusters believed to be
globular, 76 in number, were included. 5 The number of globu-
lar clusters has since been considerably extended, especially
by the later investigations of Shapley, 6 who in 1922 gave the
whole number known as 95. Many of the later additions do
not appear globular on photographs of moderate exposure,
but they reveal the typical feature of a globular cluster a
dense population of faint stars on plates made with large
instruments and long exposures. Shapley and Miss Sawyer
have divided the globular clusters into twelve subclasses, based
on the degree of apparent concentration of the stars to the center,
and probably giving an indication of the stage of development. 7
2 Astr. and Ap., 12, 689, 1893.
8 H. A., 26, Part 2, 1897.
4 H. A., 60, No. 8, 1908.
6 H. A., 76, No. 4, 1916.
6 H. B. 775, 776, 1922; 849, 1927-
7 H. B. 849, 1927.
IQ4 CLUSTERS AND NEBULAE
In the course of the researches which he describes in the
second Monograph of this series, Shapley has shown that the
globular clusters have a certain uniformity, so that their
distances and distribution may be studied by means of their
integrated apparent brightness, the brightness of individual
stars, and their apparent diameters. In conjunction with Miss
Sawyer he has obtained the necessary data on the integrated
apparent magnitudes, 8 and on the apparent diameters. 9
The ellipticities of all known globular clusters, as well as the
class and orientation to the galactic plane 9 have also
been examined by Dr. Shapley and Miss Sawyer. A considera-
tion of these data, which concern the history and internal
economy of a cluster, rather than its distance, is contained in
Harvard Monograph No. 2.
Investigations of Nebulae. After the installation of the
" Great Telescope " in 1847, the Bonds promptly began investi-
gations on the great nebula in Orion and that in Andromeda.
Early in 1848, G. P. Bond presented a paper to the American
Academy, "An Account of the Nebula in Andromeda," in which
he gave an historical account of previous investigations by other
astronomers, and the results of his own observations with the
new i5-inch telescope. Although he saw many stars in the
region, Mr. Bond did not, of course, resolve the nebula itself. 10
Later in the same year, the director, W. C. Bond, published a
paper entitled, "Description of the Nebula about the Star
Orionis." Bond was inclined to believe then that the Orion
Nebula was resolved into stars by the 1 5-inch telescope under the
best conditions. At that time, indeed, a belief prevailed that all
nebulae might be resolved with a sufficiently powerful telescope.
He made a list of stars, the positions of which were given in rec-
tangular coordinates. 11 In each of the above communications,
a careful drawing was given of the appearance of the nebula.
8 H. B. 848, 1927.
H. B. 852, 1927.
10 Mem. Amer. Acad., 3, 67, 1848.
11 Ibid., p. 87, 1848.
PLATE XVII. EXTRA-GALACTIC NEBULAE BELONGING TO THE COMA-VIRGO
GROUP. (Photographed with the Bruce Telescope.)
(Facing page 194)
PLATE XVIII. STAR FIELD IN CYGNUS, SHOWING THE NORTH AMERICA
NEBULA AND THE FILAMENTARY NEBULA.
INVESTIGATIONS OF NEBULAE 195
Later the study of the Orion Nebula was again undertaken
by G. P. Bond. Aside from the intrinsic interest of the nebula
itself, certain adverse criticisms of the results of W. C. Bond's
earlier investigation led his son to devote himself for many years
to an elaborate study of this object. He began his observations
in 1857, and continued them with some interruptions caused
by his studies of the Great Comet of 1858, and by his father's
death in 1859, until his death in 1865, when the investigation
was nearly complete. It was promptly finished and prepared
for publication by Safford. The most elaborate care was
taken in the preparation of the drawing of the nebula. The
positions of a thousand stars seen in the region were given,
expressed in right ascensions and declinations, and the recog-
nized faint nebulosity was considerably extended. Bond
spared no labor in making his work as accurate as possible and
it may be safely said that the results were all that could be
attained visually with a telescope of that size. Photographs,
however, were destined soon to replace drawings in the repre-
sentation of such objects. 12
An early photographic study of the Orion Nebula was made
by W. H. Pickering on photographs taken with various tele-
scopes during the years 1886 to 1890. Mr. Pickering made a
revision of the positions of the Bond stars in the region, 38 of
which were not seen on the photographs in the given positions.
In a few cases this was caused by the obscuration of the image
of a faint star by the large image of an adjacent bright star, but
20 of the Bond stars do not appear on the plates. On the other
hand, 146 additional stars not given by Bond were found in
the region. A study was made of the intrinsic brilliancy of
different parts of the nebula, and of the isophotal contours.
One of the most interesting results was the discovery of the
great nebulous cloud in which the whole region is enveloped. 13
During the years 1866 to 1870, precise positions were deter-
mined for several hundred nebulae with a large filar micrometer
"H. A., 5, 1867.
H. A., 32, Chap. 2, 1895.
196 CLUSTERS AND NEBULAE
attached to the is-inch telescope. The list of nebulae was
selected for the most part from the General Catalogue of
Herschel. The nebulae were fully described, and for the
brighter objects spectroscopic observations were made. Several
observers took part in this investigation, especially Winlock,
Peirce, G. M. Searle, and Austin. 14 Another series of observa-
tions of nebulae was made with the same telescope during
the years 1879 to 1882, by Pickering, Searle, Upton, and
Wendell. The diameters were determined by means of a
double-image micrometer, the brightness with a photometer,
and the spectra by a direct-vision prism. 15
G. P. Bond, Coolidge, Tuttle, and Safford discovered 28
new nebulae in connection with their observation of the Bond
Zones during the years 1848 to 1863. Under the directorship
of Winlock, 13 more nebulae were found, and Pickering added
several new gaseous nebulae, which he discovered by means of
a direct-vision prism placed in front of the eyepiece of the
i5-inch telescope. The discovery of nebulae received an
enormous impetus by the introduction of photography into
astronomical research. In the early eighties, photographic
methods were beginning to replace visual observations in many
lines of investigation, and nowhere to greater advantage than
for nebulae. For such work the advantages of a photographic
doublet were early pointed out by Pickering; in the case of
faint, luminous surfaces, the wide angle and the short focus
permit very faint objects to be shown over an area much
larger, for a single plate, than is possible with other forms of
refracting telescopes. As a test of this method, Mrs. Fleming
made an examination of five plates, of exposures from one to
two hours, made with the Bache 8-inch doublet in 1888;
the number of known nebulae in the region was nearly doubled. 16
A list of all nebulae discovered at Harvard was begun in
1908. Consecutive numbers were given, from the first nebula
14 H. A., 13, Chap. 3, 1882.
H. A., 33, No. 7, xooo.
16 H. A., 18, No. 6, 1890.
INVESTIGATIONS OF NEBULAE 197
found by G. P. Bond in 1848. From 1848 to 1883, by visual
methods, 55 new nebulae were discovered, and by 1907, chiefly
by their spectral peculiarities as shown on photographic plates,
the number was increased to 108. However, with the begin-
ning of long exposures with the Bruce photographic 24-inch
doublet at Arequipa, the possibility of a very great increase
in the number of faint nebulae became apparent. A survey
of the whole sky was planned for the discovery of nebulae
and other objects, using Bruce plates of four hours exposure.
The far southern regions were photographed with such expo-
sures, but the remainder of the sky has not been systematically
covered. By an examination of the plates made from 1898
to 1901, Stewart increased the Harvard list of nebulae to 785;
and Frost later extended it to 1238, from plates made from
1903 to 1904. From an examination of Bruce photographs
having exposures of 2 h to 4*, made from 1901 to 1908, Bailey
and Miss Waterbury carried the number forward to 2897. 17
The number has recently been increased greatly by the investi-
gations carried on under Dr. Shapley. 18 Systematic nebular
studies have been maintained and nearly 10,000 new nebulae,
as yet unpublished, have been found on Harvard plates and
are being measured for magnitude, position, and dimensions.
Probably many thousands of additional nebulae will appear
on the photographs for the Harvard collection which are now
being made at the new Boyden Station in South Africa.
Numerous objects which have been classified as nebulae,
such as many of the spiral nebulae, are now known to be distinct
systems, largely stellar. The Milky Way or galactic system,
with its complicated structure of star clouds, clusters, bright
and dark nebulae, and scattered stars, is not the only stellar
system. Its nature, and that of some other systems of stars
and nebulae will be given some consideration in the next chapter.
17 H. A., 60, No. 6, 1908; 72, No. 2, 1913.
18 H. B. 773, 777, 780, 1922; 784, 1923; 808, 1924; 816, 1925; H. A., 85, No. 6,
1924.
CHAPTER XV
STRUCTURE AND DIMENSIONS OF STELLAR
SYSTEMS
THE structure, dimensions, and distances of the different
systems which make up the visible universe have long engaged
the attention of astronomers, mathematicians, and philoso-
phers. In this chapter the attempt is made to give a brief
outline only of the main contributions to this subject which
have been made by members of the Harvard Observatory.
The correct interpretation of the revelations made by
the telescope and spectroscope is often difficult. It may now
be stated with confidence, however, that the visible universe
of stars, clusters, and nebulae is not a single system, but
consists of many systems resembling each other in greater or
less degree, widely separated, and relatively independent. It
is natural that our first and chief interest should be directed
toward the galactic system, which contains our sun as one
of its units.
Peirce's Survey of the Galactic System. The first
attempt at the Harvard Observatory to determine the form of
the Milky Way, or the galactic system, was made by Charles
S. Peirce. In connection with his photometric work undertaken
during the administration of Joseph Winlock, in the years
1871 to 1875, Peirce made a study called "Form of the Galactic
Cluster.' ' He states that "The chief end of observations of
the magnitudes of the stars is to determine the form of the
cluster in which our sun is situated," meaning the galactic
duster. Without attempting numerical accuracy, he endeav-
ored to show the general form of the surfaces of equal star-
density throughout the cluster.
198
PICKERING'S STUDIES OF THE MILKY WAY 199
Peirce first discussed the subject on the assumption that
the proportion of stars of different absolute magnitudes is
the same throughout space; and afterwards, how far the con-
clusions thus derived are affected by the assumption of the
greatest variety in the magnitudes. He divided the whole
sky into 32 equal regions, consisting of the north and south
polar regions, a central Milky Way zone, and four intermediate
zones parallel to the galactic equator. Each zone was divided
into six equal parts. A discussion was then made of the
number of stars from the first to the sixth magnitude in each
region, using Behrmann's and Heis' maps. His results
appeared to indicate that the intermediate regions adjoining
the polar regions had no more stars than the polar regions,
and that the intermediate regions adjoining the galactic
central zone had about the same number of stars as the galactic
zone. This he explained on the hypothesis that between the
zones adjacent to the galaxy and those adjacent to the polar
regions, the line of sight is nearly tangential to the surfaces
of equal condensation.
Peirce also found that for stars from the first to the sixth
magnitudes the mean distances as calculated from the proper
motions of Madler were nearly as the square roots of the
distances deduced photometrically.
The investigation was of a pioneer nature, founded on scant
data. No reference was made to the clustering tendency
of the stars in the Milky Way, nor to the presence of obscuring
clouds, at that time probably unsuspected. 1
Pickering's Studies of the Milky Way. Considerable
work bearing on the structure of the Milky Way was done by
Pickering during his long directorship. Discussions regarding
the distribution of stars of different spectral types have already
been referred to under the subject of Spectroscopy. In
connection with his photometric catalogues, Pickering discussed
the distribution of stars of different magnitudes. Dividing
the stars into groups half a magnitude apart, he studied the
1 H. A., 9, Chap. 5, 1878.
200 STRUCTURE AND DIMENSIONS OF STELLAR SYSTEMS
distribution of the 4193 stars of the early Harvard Photometry,
together with that of the 324,000 stars of the Northern Durch-
musterung, and the 7363 stars of the Uranometria Argentina.
Pickering found the actual number of stars observed was less
than that indicated by theoretical considerations, on the
improbable but convenient assumptions that the stars are of
equal brightness and uniformly distributed in space. 2
Pickering's discussion was carried forward later with increased
data. The density of the Milky Way was determined from
counts of the stars of different magnitudes. Good deter-
minations of magnitude had been made of all stars in the sky
to magnitude 7.0 or 7.5. For fainter stars the revised magni-
tudes of the Northern Durchmusterung were also used to about
the tenth magnitude, and were fairly reliable. A few still
fainter stars were provisionally employed. The proportion of
galactic stars to nongalactic stars was found to be about two
to one for stars to magnitude 7.5, the ratio increasing somewhat
for fainter stars. The number N of stars of each magnitude
in the sky was also given, which followed closely the formula,
log N = 0.5 1 M + A, the coefficient of M decreasing, however,
for fainter magnitudes. The really faint stars, which form
the galactic clouds, were beyond the reach of this discussion. 3
Miscellaneous Investigations of the Milky Way.
Minor contributions to the structure of the Milky Way were
made by Bailey, who prepared a photographic map of the
southern Milky Way in nine charts, each covering an area of
about 30 by 40. The photographs were obtained with a
Cooke lens of 1.5 inches aperture and 13 inches focal length.
Each plate was adjusted so that the longer axis was perpen-
dicular to the central line of the Milky Way. The original
photographs were made at Hanover, South Africa. Mr.
L. G. Schultz assisted in the photographic work. The exposures
were on the average about 12 hours. 4
2 H. A., 14, Chap. 14, 1884.
3 H. A., 48, No. 5, 1903.
4 H. A., 72, No. 3, 1913.
SHAPLEY'S MEASUREMENT OF THE GALAXY 20 1
A similar task was carried out by Bailey at Norwell, Massa-
chusetts, for the Northern Milky Way. Because of the amount
of artificial illumination, long exposures could not be made
at Cambridge. Nine charts again show the northern regions,
with some overlapping. Altogether, the 18 charts show the
whole Milky Way, presenting clearly the familiar cloud forms
and the dark obscured areas. 5
To compare the density of the stars in the richest parts
of the Milky Way with that at the galactic poles, a count was
made by Bailey at Areqiupa of the number of stars obtained
on Bruce plates, with exposures ranging from i* to 6 h . Expo-
sures of i 8 showed stars to magnitude 10.1, and exposures of
6*, to magnitude 19.2. For the Milky Way region, one square
degree was chosen in Sagittarius. The ratio of the number of
stars in this area to the number at the south galactic pole
varied from 2, for stars brighter than magnitude 9.5, to 1 60 for
stars at the sixteenth magnitude. The presence of vast obscur-
ing clouds in the Milky Way was pointed out. 6
William H. Pickering made an attempt, in 1917 and 1918,
to find the distance of the Orion Nebula and the Pleiades, by
the use of the known relations between absolute magnitude and
spectral type. The results obtained, however, are not in very
good agreement with other and later determinations. 7
Shapley's Measurement of the Galaxy. When Dr.
Harlow Shapley became director of the Harvard Observatory
in 1921, he had already spent several years in systematic
research looking toward the solution of the various problems
concerned in the structure and size of the visible universe.
The investigations naturally centered about the galactic system,
whose size was soon found to be vastly larger than had been
formerly believed by astronomers. It was apparent that
the ordinary means of finding parallaxes must fail, when the
depths of the Galaxy were to be sounded. Neither trironomet-
5 H. A., 80, No. 4, 1916.
6 H. C. 242, 1922.
7 H. C. 205, 1917; 206, 1918.
202 STRUCTURE AND DIMENSIONS OF STELLAR SYSTEMS
ric methods based on the earth's orbit or on the sun's path, nor
spectroscopic parallaxes, would suffice for the study of the more
distant stars. In photometric methods Shapley found the most
hopeful outlook. However vast the distance of a star, the
apparent magnitude compared with the absolute magnitude
will yield the distance by a simple computation. The apparent
magnitude can be found readily by visual or photographic
photometry. To find the absolute magnitude is more difficult.
By known methods of analysis the absolute magnitudes and
distances of eclipsing binary stars can be found, but their
number is small. Shapley placed his chief reliance on a study
of the Cepheid variables, which thus became of the highest
importance in his investigations. Fortunately, many Cepheid
variables were already known, in the Galaxy itself, in the
globular clusters, and in the Magellanic Clouds.
MissLeavitt had shown in 1912 that for 25 Cepheid variables
in the Small Magellanic Cloud the length of the period had a
close relation to the apparent magnitude; 8 and, since all the
stars in this Cloud are evidently at about the same distance,
the relation holds true for absolute magnitudes. By extended
investigations, Shapley showed that this period-luminosity
relation, or curve, was true not only in the Small Magellanic
Cloud, but was of universal application. The possibility was
at once presented of finding the distance, however vast, of any
cluster or aggregation of stars, provided Cepheid variables
could be found among its units. From the period-luminosity
curve the absolute magnitude could be directly read for any
variable whose period had been found; and the distance,
expressed in light years, could be derived by the formula
log d = 1.514 0.2 (M m).
In a long series of papers, 9 Shapley gave his results on the
determination of the distances from the sun of many celestial
objects. At first he gave special attention to the globular
8 H. A., 60, No. 4, 1908; H. C. 173, 1912.
9 Mt. W. Contr. 115-117, 126, 129, 133, 151-157, 160, 161, 175, 176, 190, 1915-
1920; Mt. W. Comm. 18, 19, 34, 37, 39, 44, 45, 47, 54, 62, 63, 64, 69, 1915-1920.
SHAPLEY'S MEASUREMENT OF THE GALAXY 203
clusters, their distances, their relations to and distances from
the galactic plane, as well as their form, size, and constituent
units. Certain globular clusters contain many Cepheid vari-
ables, others none, as shown chiefly by Bailey's studies of
Harvard plates. Shapley found, however, that the derivation
of parallaxes could be made independently of the variables by
substituting the magnitudes of the brightest stars in the cluster
as the criteria of distance. The difference between the median
magnitude of the variables in a cluster and the mean magnitude
of the twenty five brightest stars proved for practical purposes
to be nearly constant. For seven well-known globular clusters,
the median magnitude of the brightest stars near the centers was
1.28 magnitudes brighter than the median magnitude of the
cluster type Cepheid variables, with only small individual
deviations. The investigation was thus extended to the
globular clusters which contained no recognized variables.
The parallaxes having been determined, it is easy to obtain
the dimensions of the clusters. Their average diameter
is given as about 150 light years. They are enormous stellar
systems composed of many thousands of stars, vastly more con-
densed near the centers than are the stars in the vicinity of
our sun. In most cases, as shown at Harvard and Mount Wil-
son, the form is not strictly globular, but somewhat flattened,
an oblate spheroid, indicating a revolution about the shorter
axis. Such a system placed with its center in the position
of our sun would extend in all directions a distance of some 75
light years, and would envelop hundreds of our nearest stars.
The distances of the globular clusters from the sun are from
about 15,000 to about 200,000 light years. They form an
immense spheroidal or ellipsoidal group whose central plane
appears to coincide with that of the galactic system. The
center of both systems is probably in the direction of Sagittarius
at a distance of some 40,000 light years or more, a conclusion
differing widely from the view formerly held by astronomers
that the sun is near the center of the Galaxy. 10 Notwithstanding
10 Sci. Amer. Mon., p. 341, October, 1921.
204 STRUCTURE AND DIMENSIONS OF STELLAR SYSTEMS
their immense size and wide distribution, the globular clusters
appear to have such an intimate relation to the galactic system
that they may be regarded as roughly indicating its dimensions
and outlining its form.
Since he became Director of the Harvard Observatory, Dr.
Shapley has continued to give especial attention to the above
and related problems. A summary of his recent work and
present plans can best be given in his own words:
Ever since the study of the space distribution of globular clusters
indicated the eccentric position of the solar system in the Galaxy, I have
desired to investigate in detail those distant regions in the southern
Milky Way where the center of the galactic system appears to be. The
usual statistical methods of elucidating galactic structure from rather
indiscriminate counts of stars and from measures of motions in the solar
neighborhood seem to be too limited wholly inadequate, in fact, for
analysis of regions some twenty to a hundred thousand light years distant.
The so-called Kapteyn universe, for instance, is deduced without regard
to local clustering, and it combines the data from all galactic longi-
tudes; many earlier attempts to outline the system did not even allow
for differences in galactic latitude. The Milky Way system is obviously
a conglomerate of single stars, groups of stars, clusters and great star
clouds, seriously obscured in certain regions by nebulosity. A direct
attack on the problem of the distances of the individual stars in the
Milky Way, of the individual nebulae, and of stellar groups, by methods
that reach far and give unambiguous results, appears to be the most
satisfactory way of working out the details of galactic dimensions and
structure, and in particular of determining the nature of the central
regions of the galactic system . . .
As a preliminary, it should be recalled that all the known globular
clusters, about a hundred in number, form a unified considerably flattened
system of still higher order, symmetrical with respect to the galactic
plane. Their distances range from fifteen thousand to about two hundred
thousand light years, and the greatest diameter of the system, in the
plane of the Galaxy, is between two hundred thousand and three hundred
thousand light years. The center of the Galaxy is in the direction of
galactic latitude o, galactic longitude 327, and it is so remote that a
very asymmetrical apparent distribution is imposed on the globular
clusters, which thus appear concentrated in Scorpio, Sagittarius, and the
surrounding constellations. Also there appears to be a decided concen-
tration of other remote and highly luminous objects in the same region
SHAPLEY'S MEASUREMENT OF THE GALAXY 205
of the sky, probably the result of the great depths of the Galaxy in the
direction of the center, rather than of a real clustering of such objects
around the center.
Since the globular clusters are probably good indicators of the form of
the Galaxy, of which they are a part, we conclude somewhat tentatively
that galactic objects lie in an irregularly circular and much flattened
system a discoidal affair populated by probably not less than io 11 stars
(one hundred billion). Its dimensions may be greater or less than those
of the surrounding and concentric system of globular clusters. It is our
problem to discover the extent of the Galaxy by direct measurement,
instead of continuing to base our estimates largely on the distribution of
the globular clusters.
Increasing knowledge of the absolute luminosity of variable stars
increases also their usefulness in measuring distances, whether inside the
Galaxy, or outside, in globular clusters, Magcllanic Clouds, and extra-
galactic nebulae. It now appears that typical Cepheids, cluster type
variables, long period variables and to a more limited extent novae and
eclipsing binaries, can all be used in the work on galactic dimensions.
Ultimately we may use also the planetary nebulae, the open clusters,
peculiar types of variables, and stars of extraordinary spectrum and color
in this work; and certainly the integrated magnitudes and angular dimen-
sions of globular clusters and extra-galactic nebulae are among the most
potent measuring tools, though they are only indirectly used in the present
study of galactic structure.
In order to provide material for the general study of faint variable stars
as bearing on the Milky Way problem, an extensive observing program
was inaugurated about five years ago at the Harvard Observatory." 11
This work is being carried on energetically, and several
hundred new galactic variables have been found.
For purposes of study the Milky Way was divided into 240
star fields. An investigation has already been made by Dr.
Shapley and Miss Swope of one of these fields, No. 185, situated
in Scorpio and Ophiuchus. In this star cloud the periods of 26
cluster type variables were determined. The distance to the
center of this cloud, derived from these variables, is about
47,000 light years, which is the same within admitted errors
as the distance previously found for the center of the system of
globular clusters, and as the center of the galactic system.
11 Proc. Nat. Acad. Sci., 14, 825, 1928.
206 STRUCTURE AND DIMENSIONS OF STELLAR SYSTEMS
It thus appears that in exploring the rich star cloud in Scorpio and
Ophiuchus, as shown on Milky Way Field 185, we have been measuring
a portion of the central nucleus of the Galactic System. 12
Details of the Solar Neighborhood. Several minor con-
tributions to the structure of the galactic system have been
made by different members of the Observatory.
King has discussed the possibility of a local cloud of absorb-
ing matter. That large areas in the Milky Way are obscured
by dark clouds is now a matter of common knowledge. King
brought together considerable evidence in favor of the hypo-
thesis that a local cloud of absorbing matter, extending from
the sun to a distance of at least 100 light years, pervades our
local cluster. 13
Luyten has made a study of the nearby stars, those considered
nearer than 10 parsecs; 104 such stars were found. Among
the products of this investigation are, with certain assumptions:
the sun's velocity through space is 25 km/sec; the total mass
of the Kapteyn System is 1.4 X io 9 times the sun's mass;
number of collisions in the Kapteyn System is 1.4 X io~ 13
per year. 14 The work was supplemented by a study of southern
stars nearer than 25 parsecs. 15 Luyten has also made a study
of the brighter M type stars, 16 of absolutely bright stars in the
vicinity of the sun, 17 of groups of connected stars, 18 and of the
proper motions of stars. 19
The Magellanic Clouds. It is evident that although great
advance has been made in the solution of the problems involved
in the dimensions of the galactic system, much time must
yet elapse before all the material necessary for the completion
of Shapley's investigations, outlined above, can be obtained.
12 Ibid., p. 830.
13 H. C. 299, 1927.
" H. A., 85, No. 5, 1923.
"H. C. 251,1924.
18 Ibid., p. 273.
17 H. C. 274, 1925.
18 H. C. 298, 1926.
H. C. 283, 1925)293, 1926.
THE MAGELLANIC CLOUDS 207
Meanwhile, even more rapid progress has been made in the
study of the Magellanic Clouds, two isolated stellar systems
in the far southern sky. It appears somewhat anomalous
that distant systems can be investigated more readily than
our own system of which we are a part. Our outlook, however,
is rendered more complicated from our position within the
galactic system. An outside view would have many advan-
tages. If we might be placed at a distance of half a million
or a million light years, so that we could view the galactic
system as a whole, the problems as to size and form would be
much more simple.
The Magellanic Clouds have the appearance of detached
parts of the Milky Way. They are plainly visible to the
unaided eye on a moonless night, but practically disappear
in full moonlight. Like the Milky Way, these Clouds are
composed of faint stars, nebulae, and clusters.
Much attention has been given to the Magellanic Clouds
by astronomers, notably by Dr. Shapley. The accumulation
of data concerning them was actively begun during the admin-
istration of Pickering. Photographs of both Clouds were
obtained with various instruments soon after the establishment
of the southern station at Arequipa, in iSQi. 20 It was early
recognized that certain features associated the Clouds with
the Milky Way. For example, of all the stars known to be
of the fifth type (Class O), having spectra with bright bands,
about 80 are found near the central line of the Milky Way
and more than 30 in the Magellanic Clouds. 21 Great numbers
of variables also have been found in the Clouds, as well as in
some globular clusters and in certain areas of the Milky Way,
as described in Chapter XIII.
A relationship between the galactic system and the spiral
nebulae, although often suspected, is not obvious. Neverthe-
less, some resemblances exist. Shapley has made a comparison
of the spiral nebula Messier 33 and the Large Magellanic
20 H. A., 26, Part 2, 1897.
21 H. A., 56, 177, 1912; H. B. 801, 1924.
208 STRUCTURE AND DIMENSIONS OF STELLAR SYSTEMS
Cloud concluding that "These comparisons, though admittedly
provisional, are sufficient to justify classing the Magellanic
Clouds with the spirals." Since resemblances between the
Magellanic Clouds and the galactic system have already been
shown, it seems evident that all these varied groups, if not
always to be regarded as sister systems, may at least be accepted
as cousins or second cousins in the celestial family. 22
Shapley issued in May 1924 the first of a series of papers
treating of the distance, size, and structure of the Magellanic
Clouds. Preliminary investigations by Hertzsprung and
Shapley had revealed that the parallaxes of the Clouds were
not larger than a few hundred thousandths of a second of arc,
far beyond the reach of trigonometric methods. The stars,
also, are too faint for the determination of spectroscopic
parallaxes. Photometric methods must therefore be employed.
Fortunately, there was no lack of Cepheid variables. The early
photographic magnitudes of Miss Leavitt, although in general
good, needed a change of about one magnitude in the zero
point. An elaborate revision of the early magnitudes was
carried out, and new sequences of stars were added in the
Small Magellanic Cloud. In all, photographic magnitudes
were determined for 25 sequences in the Small Cloud, including
about 400 stars, ranging in magnitude from 6.73 to below the
seventeenth magnitude.
The determination of the distance of the Small Cloud
was made by a comparison of the apparent photographic
median magnitude with the absolute median magnitude deduced
from the period-luminosity curve. The mean value of the
distance is approximately 100,000 light years, with an estimated
probable error of 15 per cent. The average angular diameter
of the Cloud is 3. 6, which corresponds, with the above value
of the distance to about 6000 light years.
Accepting R. E. Wilson's determination of the motion of the
Small Cloud in the line of sight as +170 kilometers a second,
Shapley points out that this corresponds to 165 parsecs in
22 H. B. 816, 1925.
THE MAGELLANIC CLOUDS 209
a million years. On the assumption that the velocity of
recession has been the same in the past, he finds that the
Small Cloud was in or near the plane of the Milky Way in the
year 1.9 X io 8 , or 190,000,000 years ago. This result
leads to interesting possibilities in regard to some of the star
clouds of our present Milky Way.
The brightest stars in the Small Cloud have apparent
photographic magnitudes between io and 12. It follows from
the above parallax that their absolute magnitudes exceed
5.5, occasionally as high as 7.0, fifty thousand times as
bright as our sun. 23
Many additional results of striking interest were obtained
later in regard to stellar magnitudes in the Small Cloud.
Shapley finds that in this Cloud occur some 300 stars, whose
visual absolute magnitudes are brighter than 7.0, and
260,000 stars with absolute magnitudes brighter than zero. A
luminosity curve for the giant stars was determined with the
assistance of Miss Ames from a study of 6,800 stars, in six
regions each containing a magnitude sequence. A curve for
each region was derived, as well as the general luminosity curve
for the whole. The brightest stars in the Small Cloud were
found to be photographically between 10.5 and 13.5, corre-
sponding to absolute photographic magnitudes 7 and 4.
The absolute magnitude zero corresponds to the apparent
photographic magnitude 17.5. Integrating the light of all
the stars, except those fainter than 18.0, the total apparent
photographic magnitude appears to be about 2.0, possibly
no greater than 3.0. The total absolute magnitude of the
Small Cloud, excluding stars fainter than 18.0, is of the order
of -is. 24
Similar investigations were made of the Large Magellanic
Cloud. Using methods similar to those referred to above for
the Small Cloud, Shapley found the provisional parallax of the
Large Cloud to be o".oooo29. This would place the Large
23 H. C. 255, 1924.
24 H. C. 260, 1924.
210 STRUCTURE AND DIMENSIONS OF STELLAR SYSTEMS
Cloud at a distance of 34.5 kiloparsecs, or 112,000 light years,
somewhat more distant than the Small Cloud. The average
diameter of the Large Cloud is 7. 2, corresponding to 4.3 kilo-
parsecs, or nearly 14,000 light years. Its radius is thus about
ten times the probable distance of the earth from the Orion
Nebula. The distance between the two clouds is about 12
kiloparsecs, or nearly 40,000 light years, a distance greater than
that from the earth to the Hercules Cluster. 25 Later work
by Shapley, Miss Sawyer, and Miss Ryder, as yet unpublished,
indicates a somewhat larger parallax for the Large Cloud.
The completion of five sequences of comparison stars in the
Large Cloud, and the derivation of the parallax as given above,
permitted the determination by Shapley of the absolute
magnitudes of the various objects in the Cloud. The absolute
magnitudes for 9 stars of the P Cygni type lie between 3.2
and 7.9. The absolute magnitudes of at least 20 invariable
stars appear to be brighter than 8. Miss Leavitt found 808
variable stars in this Cloud, and others have been added by
different observers. Five clusters surely globular, and two or
more others doubtfully so, are found in the Large Cloud. The
mean apparent photographic magnitude of the five globular
clusters is 9.2, corresponding to the absolute photographic
magnitude 8.5. This probably corresponds to an absolute
visual magnitude of 9.1. The mean absolute visual magni-
tude found for globular clusters outside the Magellanic Clouds
is 8.8. The agreement is as close as could reasonably be
expected. The most striking object in the Cloud is 30 Doradus,
the well known nebula N. G. C. 2070. The integrated absolute
magnitude is about 14, making it ten or eleven times brighter
than the Orion Nebula. The diameter of the brighter portions
of 30 Doradus is 20 parsecs, and of the whole nebula, including
the faint extensions, about 40 parsecs. Placed as near to the
earth as the Orion Nebula, it would have an apparent magni-
tude of 7.5, and would cast strong shadows on the earth. 26
25 H. C. 268, 1924.
28 H. C. 271, 1925.
EXTRA-GALACTIC SYSTEMS 211
In a later discussion of the Magellanic Clouds, the absolute
magnitudes and diameters of 108 diffuse nebulae in the Small
Cloud were given. The average absolute magnitude for the 108
nebulae is 5.3 o.i. The average linear diameter of 106
nebulae is 5.0 0.2 parsecs. A second list increased the num-
ber of nebulae in the Small Cloud by iyo. 27
The period-luminosity curve hitherto used was referred to
median visual magnitudes. Since its practical use had become
almost exclusively photographic, a well determined photo-
graphic period-luminosity curve was needed. The visual curve
published in 1917 was based on material derived from globular
clusters and the Small Magellanic Cloud. For the new
determination of the photographic curve, Shapley, aiming
at more homogeneous material, used only photographic data
derived from the Small Magellanic Cloud. The reduction was
based on 107 variables well scattered throughout the Cloud. 28
In the study of the Magellanic Clouds, it is important to
distinguish between the stars comprising the foreground and
those belonging to the Clouds. The conclusion drawn from a
study of this problem, based largely on the spectral composition
of the foreground and of the brighter objects in the Clouds,
was that we have no definite evidence of stars in the Small
Cloud brighter than apparent magnitude 10.0, or absolute
magnitude 7.5, whereas in the Large Cloud it is probable
that 20 or 30 stars are brighter than apparent magnitude
9.0. Further spectroscopic investigations on this subject are
planned. 29 Dr. Shapley was assisted in one or more of his
later papers on the Magellanic Clouds, referred to above, by
Harvia H. Wilson, Issei Yamamoto, and Margaret L. Walton.
Extra-gakctic Systems. The method of determining
distances by the use of the period-luminosity curve of variable
and other stars, made of universal application by Shapley, has
been used to extend our knowledge of extra-galactic objects
27 H. .275,276, 1925.
28 H. C. 280, 1925.
w H. C. 288, 1925.
212 STRUCTURE AND DIMENSIONS OF STELLAR SYSTEMS
revealed to us by the telescope. By such means it has been
found, especially by Hubble of the Mount Wilson Observa-
tory, that the spiral nebulae lie far beyond our local system,
and that they form independent stellar systems, whose distance
from the earth must be expressed in many cases in millions of
light years. Our nearest neighbors among stellar systems are
the Magellanic Clouds at about a hundred thousand light years.
A very few bright spirals, such as the great spiral nebula in
Andromeda, probably are somewhat less distant than one
million light years. Accepting the general truth of these results,
it appears that the faintest spirals which can be photographed
must be situated at a distance not less than one or two hundred
million light years.
Such in general is the size of our visible universe, so far
as we have the means to extend it at this time. The Harvard
Observatory has long been at work in the effort to make a
survey of the sky, using long photographic exposures, in order
to reach the faintest extra-galactic objects possible. The
Bruce 24-inch doublet has been found well suited to this survey,
although the great reflectors may well extend the investigation
to fainter objects in special limited areas. The nature of
many of the structureless nebulae, which are shown on photo-
graphs of long exposure, is not yet known.
Shapley has made a classification of the extra-galactic nebulae,
suited to the work of the Bruce telescope, which has probably
photographed more nebulae than any other single instrument.
He has chosen as the significant descriptive information for
extra-galactic nebulae: position, total magnitude, size, form,
orientation, concentration, and, for a few, an indication of
irregularity in form or concentration, and the presence of spiral
structure. 30
Out of more than twenty thousand catalogued extra-galactic
nebulae, more than a fourth have been found and described
at Harvard. Nearly ten thousand more have been recently dis-
covered on Harvard photographs but not yet completely studied
*>H. B. 849, 1927.
PLATE XIX. HARLOW SHAPLEY.
313)
EXTRA-GALACTIC SYSTEMS 213
and published. Shapley found 850 nebulae on a single Bruce
plate, of six hours exposure, at 22* 40, 45, in a region of 30
square degrees. 31
Shapley and Miss Ames obtained especially interesting results
in the study of a cluster of bright spiral nebulae at approxi-
mately 12* 2o m , +13. The distance to the center of the whole
group is given as probably of the order of ten million light years,
and the diameter of the group, as two million light years. No
better example can be given of the magnitude of the problems
presented to modern astronomers, when it is considered that
this cluster is one of the brighter groups of the extra-galactic
nebulae. As a by-product of this investigation, Shapley found
that, in confirmation of his earlier investigations and of the
work of Lundmark and Lindblad, the scattering of light in
space, if any, is too small to be appreciable. 32
The term " island uni verses " has been applied to these out-
lying stellar systems, such as the Magellanic Clouds, and the
great spiral nebula in Andromeda. The term is objectionable
since "the uni verse " is one, but its use is unimportant if the
truth is understood. Our "universe/' the galactic system,
appears at present to be by far the largest system known. As
Shapley has aptly expressed it, where other systems are known
as islands, the galactic system is a continent. Yet such a
system as the Andromeda Nebula, with a diameter of some
45,000 light years, is no mean rival; while, far more distant
and appearing only as faint flecks of light, equally large, or
even greater systems may exist. It is evident however, that,
whether we live in a limited universe or not, there is a definite
limit beyond which our observations cannot reach. Within
this realm lies the province of astronomy; what exists beyond
may well be left to the mathematician and the metaphysician.
31 H. B. 784, 1922.
32 H. C. 294, 1926.
PART III
BIOGRAPHICAL SKETCHES
CHAPTER XVI
THE BONDS
THE first four directors of the Observatory, William C. Bond,
George P. Bond, Joseph Winlock, and Edward C. Pickering,
held the office respectively for 20, 6, 9, and 42 years. They all
died in office. During the brief intervals that elapsed between
successive directors, the Observatory was in charge of the rank-
ing assistant. The fifth and present director of the Observa-
tory (1927) is Harlow Shapley.
The early history of the Observatory is largely a record of the
personal achievements of the Bonds, who controlled its destinies
for 26 years. That it became a research institution rather
than a teaching department of the College is due in no small
degree to them. A brief account of their lives is given in the
present chapter.
William Cranch Bond, 1789 to 1859 ; Director, 1839 to
1859. William Cranch Bond was descended from a prominent
family of Cornwall, England. His mother's family, from
whom he received the name Cranch, was from the neighboring
county of Devonshire. His father, William Bond, visited
this country in 1784, and lived for a time in Boston, where,
in 1785, he was made a free citizen of Massachusetts by special
act of the General Court. He chartered a brig and came to
Boston again in 1786, bringing his family. Later he established
himself in Falmouth (now Portland, Maine) and engaged
in the business of shipping lumber to Bristol, England. This
venture, however, was unsuccessful, and in 1790 he removed
to Boston and began business as a watch- and clock-maker, a
trade he had learned in London. When Mr. Bond brought
his family to Massachusetts, he had two children living, two
having died in infancy. In America two more children were
217
218 THE BONDS
born, a daughter, Hannah Cranch Bond, and, sixth and last,
William Cranch Bond.
William Cranch Bond was born in Portland on September
9, 1789. His childhood and youth were periods of disappoint-
ment, hardship, and struggle, due to poverty. The business
established by his father in Boston developed very slowly
and needed all the assistance he could give. He was obliged
to leave the public schools at an early age. To a sensitive
and studious boy this was a heartbreaking sacrifice. But
however hard his daily routine labor, he found some time for
study and improvement. He had a rare mechanical ability,
which was manifested in early childhood by his skill in making
toys and other things of special interest to boys.
At the age of fifteen, while actively employed in the work
of his father's shop, Bond constructed a useful chronometer.
He had no model, but followed a description, which he had
found in an old French book, of the chronometer used by the
navigator Perouse. In the absence of a suitable spring he
used weights, so that the chronometer was serviceable for use
only on land. But in 1812, at the age of twenty three, he
made an excellent ship's chronometer. His attention was
irrevocably fixed on astronomy by the remarkable total eclipse
of the sun in 1806, when he was seventeen years of age.
The following extracts from a communication made by
his son, George P. Bond, to Hon. Edward Everett in 1859,
just after the death of his father, throw light on the early
struggles of William Cranch Bond:
I have always understood that his situation up to manhood, and even
for years after, was one of peculiar trial and hardship. It was at this
period of life, usually so full of animation and buoyancy, that he speaks
of himself as "nearly heart broken and in despair of ever being able to
accomplish anything." The expression bespeaks the sensitiveness of his
disposition, and a dejection unnatural in one so young. His mother,
Hannah Cranch, as was fit, was ever the confidante of his plans, and the
consoler of his distress. She was a woman of well-cultivated mind and
high excellence of character; one who could sympathize in his high aspira-
tions, though she could not relieve the pressure of adversity.
PLATE XX. WILLIAM CRANCH BOND.
(Facing page 218)
WILLIAM CRANCH BOND 219
In his boyhood a modest reserve and a quick sensitiveness were as
prominent as in later life; yet there was a resolute spirit beneath this veil,
or he would never have risen superior to frowning fortune. This simplicity
of manner and shrinking from ostentatious display did not wholly conceal
from his playmates a consciousness of superior capacity; he could be
silenced easily, but rarely diverted from his purpose. A design once
formed in his mind seemed to become a part of his very being, and was
pursued with an unfaltering aim. To this invincible perseverance he
owed everything. It is not for us to condemn his persistence, sometimes
beyond the bounds of reason, in his original convictions. Whatever he
accomplished was done in a quiet, unobtrusive way; but if opposed, a
determined, persevering energy was manifested, equal to any emergency,
and seldom to be disappointed of its end. These are said to have been the
traits of his boyhood they certainly characterized his after life.
His first astronomical apparatus was a sundial and pieces of string held
at arm's length, with which he plotted the stars and comets, after the
fashion of Ferguson. These were succeeded by other contrivances better
adapted to the purpose. It is a fact not without interest that for many
years preceding the war of 1812, the period of our greatest commercial
prosperity, the "rates" and "errors" of nearly all the chronometers
employed in the foreign trade of Boston were derived from instruments
made by his hand.
The history of his (independent) discovery of the Comet of 1811 shows
him at that time as an attentive observer of the heavens. He had pre-
viously, for want of a telescope, been in the practice of going to a deep well,
and, shading his eyes from stray light, would direct his eyes toward the
bottom for some minutes, and with this preparation faint objects among
the stars were more easily distinguished. Instead of attempting to
acquire reputation from the discovery, he was so careless on this point that
it took months for the intelligence to travel four miles to Cambridge. On
the other hand he applied himself most industriously to collecting observa-
tions with such apparatus as he could command. To watch the motions,
and record the positions of the heavenly bodies, was an occupation per-
fectly congenial to his tastes, which evidently brought with it its own
reward. It was his constant practice, from the time when he first came
into possession of appropriate instrumental means, to record astronomical
phenomena, often with no other apparent motive than a love of the
occupation. For thirty years this was done, not merely without compen-
sation, but to his manifest pecuniary disadvantage. This consideration,
it is probable, never entered his mind.
In this period we find him zealously tracing the courses of comets,
collecting observations of lunar culminations, occultations, and eclipses
of the Sun, determining by different methods the position of his observa-
220 THE BONDS
tory and connecting it by trigonometric surveys with neighboring points,
and in other ways evincing the strength of the ruling passion by the sacri-
fices which were made to gratify it. Nor was his attention confined to
astronomy; the kindred sciences of meteorology and magnetism were not
neglected. Even on his journeys it was his custom to take with him a
sextant and artificial horizon and a chronometer to find the latitudes and
the longitudes of the places visited.
The longitude of his observatory in Dorchester, adopted just thirty
years since, agrees precisely with the latest determination of the position
of the observatory of Harvard College, allowing for the difference of
meridians. The latitude also presents as exact an accordance as could be
attained with the instruments in his possession, confirming his remark:
"I was satisfied that no repetitions with the instruments would have given
me greater confidence in the results." In the first house which he owned
(in Dorchester) the only parlor was sacrificed to science, and forthwith
converted into an observatory. A huge granite block, some tons in
weight, rose in the centre of the room, and the ceiling was intersected by a
meridian opening. My recollection will just carry me thirty years back
to this room and its mysterious paraphernalia. I can recall, too, in the
garden and neighboring fields the stone blocks for the support of instru-
ments, meridian marks, etc. Like the men of old, wherever he sojourned a
stone was set up as a memorial. His antipathy to an insecure foundation
many would have thought extravagant: the tremor of an instrument would
annoy and fret him as a harsh discord does the cultivated ear of the
musician.
Every year, as his means allowed, some addition was made to the
resources for observation; but adversity still waited on him, and he was
obliged, as a constant practice, after the whole day had been devoted to
business, to spend hours at his work bench. He made it, in fact, a rule
of life to earn enough by his nightly labor at his profession as a watch
maker to meet the current household expenses. That so much industry
and application should have failed in placing him in a position of compe-
tence will not surprise any one acquainted with his methods of conducting
business transactions, for which, as far as his own pecuniary advantage was
concerned, he had no capacity. The making of a good bargain was to him
the most incomprehensible of problems.
Between 1825 and 1830 Bond made an investigation of
the comparative rates of marine chronometers at sea and on
land. He established the fact, at that time not understood,
that the chief element in their differences in rates was the
variation of temperature. His appointment by the United
WILLIAM CRANCH BOND 221
States Government, in 1838, to cooperate with the expedition
of Lieutenant Commander Charles Wilkes, was a striking
recognition of the accuracy and value of his work. Without
regard to the salary he was to receive or the amount of labor
involved, he undertook to rebuild his Dorchester observatory
in order to make the results worthy of his own ideals. The
following year, 1839, through the direct personal influence of
President Quincy, he was persuaded to transfer his equipment
to the Dana House Observatory and undertake the duties of
Astronomical Observer to Harvard University.
At the date of this interview the President found Mr. Bond well estab-
lished in a profitable manufacturing business, happily situated in his
domestic and neighborhood surroundings, with an avocation fascinating
enough to occupy all his leisure, and a fame extensive enough to satisfy
his own modest estimate of his abilities. There was no pecuniary better-
ment for Mr. Bond in the suggested change. Mr. Quincy could only
offer him what he had already, a family domicile; so that the proposal
might warrant an adaptation of Sydney Smith's famous phrase, and be
described as an invitation to come to Cambridge and " cultivate astronomy
upon a little oatmeal." In so phrasing it there is no disparagement of the
College; it was the day of small things, of pennies not dollars, in the
College treasury. But the event speaks the praises of Mr. Quincy, whose
sagacity was unfailing, and before whose persuasiveness and energy
difficulties in administration were wont to give way, and of Mr. Bond,
whose unselfishness and loyalty to science were proof against pecuniary
considerations. 1
For nearly five years, while Bond remained at the Dana
House, the observations in large part were meteorological and
magnetic, although the Observatory had been regarded from
the first as astronomical. Bond, however, made many observa-
tions of occultations, eclipses, and comets. The equipment
was not such as to encourage the expansion of the astronomical
program. Added to this is the fact that, since he received no
salary from the University, Bond was obliged to carry on his
business in Boston, in addition to the obligations he had
assumed with the Government of the United States. During
1 D. W. Baker, "History of Harvard College Observatory, 1840-1890," Boston
Traveler, 1890.
222 THE BONDS
the last part of this period, also, his time was largely taken up
with the plans of the new Observatory and its equipment.
A new period began with the mounting of the large refractor
in 1847. The public expected important observations and
discoveries from the use of this instrument, then unsurpassed
in quality by any telescope in the world. Bond fully appre-
ciated the responsibility of his position. A long series of
observations was begun on the members of the solar system,
on comets, and on other important celestial objects, especially
the nebulae. The results were sufficient to bring the Observa-
tory to the attention and respect of the astronomical world.
No further proof is necessary than his election as the first
American Foreign Associate of the Royal Astronomical Society,
an honor which he received in 1849.
A detailed account of the activities of the Observatory
during his administration is given by Bond in his Annual
Reports. The first report, that for 1846, soon after the
opening of the new Observatory, contained information about
the lens for the large refractor, and a new transit circle which
had been ordered from Simms, of England. The report shows
that moon culminations and star transits had been observed
at all hours in connection with the observations made else-
where by the United States Coast Survey. Of special impor-
tance at that time were observations of transits of stars in
the prime vertical for the determination of the latitude of
the Observatory. Observations of comets, four of which
were found independently by George P. Bond, and the compu-
tation of their orbits, together with meteorological and magnetic
observations, show the indefatigable activity with which
Bond and his son and a few volunteer assistants carried
on the work of the Observatory, even before the arrival of the
principal instrument. The discovery of the dark ring of
Saturn soon after the arrival of the is-inch refractor, and later
of an eighth satellite of that planet, demonstrated the high
quality of the telescope. Detailed examinations of surface
markings of the sun and planets, and of the appearance of
WILLIAM CRANCH BOND 223
comets, clusters of stars, and nebulae served also to test the
quality of the lens and the ability of the observers.
In the midst of so much discovery, it is not surprising that
Bond's enthusiasm to make the most of the new telescope
should have led him into an error of observation. In a letter
to President Everett, September 22, 1847, he announced:
DEAR SIR:
You will rejoice with me, that the great nebula in Orion has yielded to
the powers of our incomparable telescope! This morning, the atmosphere
being in a favorable condition, at about three o'clock the telescope was
set upon the Trapezium in the great nebula in Orion. Under a power of
200, the fifth star was immediately conspicuous; but our attention was
very soon absorbed with the splendid revelations made in its immediate
vicinity. This part of the nebula was resolved into bright points of
light . . .
It should be borne in mind that this nebula and that of Andromeda have
been the last strong-holds of the nebular theory; that is, the idea first
suggested by the elder Herschel of masses of matter in process of condensa-
tion into systems. 2
Bond goes on to state that the Herschels had been unable
to resolve the nebula, and that Lord Rosse had also failed to
resolve it until he used the reflector of 6 feet aperture, when
he announced that:
1 think we may safely say, that there can be little if any doubt as
to the resolvability of the nebula. We could plainly see that all about
the Trapezium is a mass of stars, the rest of the nebula also abounding in
stars, and exhibiting the characteristics of resolvability strongly marked.
It must be remembered that at this time the spectral analysis
of such objects was unknown, and that among astronomers the
idea was general that the nebulae only awaited sufficiently
powerful telescopes for their resolution into stars. Bond
appeared to have some doubts regarding the accuracy of this
communication to President Everett, for no mention is made
of it in his annual reports or in public announcements.
To Bond and to members of his family is due the credit for the
construction of the first really satisfactory chronograph for the
2 H. A., I, cxxi, 1847.
224 THE BONDS
automatic recording of star transits. The development of
electric methods for longitude work, in cooperation with
other workers in the same field, was promoted at Cambridge,
which accordingly became the recognized center for longitude
determinations.
At the close of William C. Bond's life, the Observatory had
been brought into a state of high efficiency and occupied an
enviable position in the astronomical world. Although still
cramped by insufficient funds, it had been saved from the
possibility of failure. The results showed the wisdom of
Quincy's policy in asking Bond to direct the early years of the
Observatory. The value of his services was everywhere
recognized, as were his peculiar genius, energy, and devotion.
Bond was fortunate in his family life. His first wife was
his cousin, Selina Cranch, whom he married on July 18, 1819,
at Kingsbridge, Devonshire, during a visit to England. She
was the mother of his six children, William Cranch, Jr., Joseph
Cranch, George Phillips, Richard Field, Elizabeth Lidstone,
and Selina Cranch. His wife died in 1831, and later he married
her elder sister, who devoted herself to him and his astronomical
ambitions, making every possible sacrifice to aid his endeavors.
His children, also, were equally devoted to their father. Indeed
his passion for astronomical observation and his boundless
energy and enthusiasm seemed to sweep away all opposition
and enlist cooperation.
Some account of Bond's scientific work is given earlier in
this volume. In addition to his election as the first American
Associate of the Royal Astronomical Society, he received the
honorary degree of A.M. from Harvard University in 1842;
he was a member of the American Academy of Arts and
Sciences, and the American Philosophical Society; a correspond-
ing member of the Institute of France, and of the Accademia
dei Lincei. On his death in 1859, his friend Professor Benjamin
Peirce, of Harvard University, the foremost American mathe-
matician of his day, presented an appreciation of his life to the
American Academy of Arts and Sciences:
WILLIAM CRANCH BOND 225
. . . During seventeen years I have been Mr. Bond's colleague in Harvard
College, and this interval comprises the whole period in which he had any
favorable opportunity of astronomical observation. But his love for
the science had been shown long before he came to Harvard, and
even a quarter of a century earlier he made a careful survey of the Green-
wich Astronomy, at the request of President Farrar, with direct reference
to the superintendence of the erection of an Observatory at Cambridge
, . . When Mr. Bond returned from England he set up a small Observa-
tory of his own, where he undertook the observation of occultations and
eclipses. It was here that he developed one of the finest elements of
genuine enthusiasm and true genius, that of accomplishing much with
small means . . .
When ... he was drawn to Cambridge by the strong hand of Presi-
dent Quincy, when the cause of the Observatory was undertaken by the
unflinching and irresistible vigor of my friend, Mr. J. Ingersoll Bowditch,
when even the heavens came to our assistance, and that wonderful Comet
of 1843 excited most opportunely a universal interest in celestial
phenomena it was then apparent that the affection for Mr. Bond was the
chief strength of the occasion, and to that were we mainly indebted for
the successful attempt to obtain the unrivalled equatorial of the university
and to lay the foundations of the Observatory. In the history of American
science there is no more memorable epoch . . .
The astronomical researches of Mr. Bond while at the Observatory are
so recent that I need only allude to them. By the habits of his life his
attention was especially drawn toward the improvement of the instru-
mental means of observation. Hence, we have from him, and under his
administration first, the ingenious observatory-chair of the great equa-
torial; second, the spring-governor . . . ; third, the application of photo-
graphy to the Sun, moon, and stars.
In his original investigations he naturally restrained himself to those
forms of observation which were fully within the reach of his own resources.
He did not, therefore, seek those inquiries which could only be accom-
plished by long, intricate, and profound mathematical computations . . .
But when observations were required which must be passed over to the
computer, his skill was not wanting to the occasion. Thus, in conjunc-
tion with Major Graham, he made that choice series of observations from
which the latitude of the Observatory was determined. His observations,
and those made under his administration, upon the nebulae of Orion and
Andromeda; the interesting discoveries as to their revolution and peculiar
configuration; the researches into the physical aspects -*f the different
planets, and especially those upon the Saturnian system; and the remark-
able discoveries of the inner ring, and of the fluid 3 constitution of the
8 Both the Bowls and Professor TVrce believed the rif>s"i of Saturn to be fluid.
226 THE BONDS
rings, and of the eighth satellite, need only be named. They are known
to all; they have passed into the text books of astronomy, and our chil-
dren's children will be familiar with the name of Bond. 4
George Phillips Bond, 1825 to 1865, Director, 1859 to
1865. George P. Bond, son of William C. Bond, was born in
Dorchester, May 20, 1825. He was graduated from Harvard
College in 1845. His childhood and youth were passed in an
astronomical environment so intense as to dominate all other
influences. Some of his impressions of the life at Dorchester
have already been given in the sketch of his father's career.
A clear conception of the characteristics of his youth and man-
hood may be gained from the following extracts of notes pre-
pared at the request of Professor Holden by his daughter
Elizabeth Bond, of Cambridge: 5
We have few reminiscences of his early childhood, but I am told that he
was peculiarly gentle and lovable, a tractable, intelligent pupil, in favor
both with teachers and playmates ... A quiet, reserved, self-contained
boy, he, no doubt, did not easily make intimate friends, though he won
the respect and the liking of all ...
He was passionately fond of out-of-door life and sport, a true English-
man in his love of hunting and fishing. Until his health began to fail he
went each year on some shooting expedition, either to Maine for deer and
moose, or to the shores of Cape Cod for wild duck. He was deeply inter-
ested in ornithology, and when a lad had, for a time at least, contemplated
devoting his energies to the study of some branch of Natural history rather
than to astronomy. His elder brother's death, however, left him no
choice but to take that brother's place and to become the support and
colaborer of his father. It was not without reluctance that he resigned
his own special taste to turn his attention exclusively to the stars. So
long as he lived it was his favorite recreation to read works on orni-
thology, or to watch the birds and note their plumage, song, and
habits . . .
Some of the sweetest memories of my childhood are connected with the
happy hours spent in the garden or the fields with my father ... He
was naturally fond of children, and showed rare tact in gaining their love
and confidence . . . When a mere baby, not more than three years old,
I can remember being held out of an open window in my father's arms
4 Proc. Amer. Acad., 4, 163, 1859.
6 Edward S. Holden, Memoirs of W. C. Bond and G. P. Bond, 48, 1897.
GEORGE PHILLIPS BOND 227
as far as he could stretch safely to see an eclipse of the Moon. It was
a winter's night, and very dark and cold, and I was as much alarmed as
interested by the weird spectacle, so it made an impression on me.
The early death of his wife was a severe blow to his sensitive nature.
She was a woman of a singularly sweet, gentle disposition, and their
short married life had been very happy, though clouded by the shadow
of her fatal illness. In the course of eleven months, he lost his youngest
child, his wife, and his father, and a serious fit of illness developed in
himself, the seeds of the disease which was to cut off his own life in a few
short years. My mother died in December, 1858.
In 1859, on the death of his father, he was appointed director of the
observatory, and it was only then that the real difficulty of carrying on
the work with the insufficient means at the disposal of the observatory
became evident. The chronometer and clock business of the firm of
William Bond & Son was prosperous, and my grandfather had been able
to supply any pressing need from his own purse. But my father hid no
private resources at his own disposal, and the sums supplied him by the
funds of the institution or the liberality of a few Boston friends, were
wholly inadequate to meet the wants of the observatory. Expenses were
curtailed as far as possible, especially those of his own household, but
the weight of care and anxiety pressed more heavily with each succeeding
year. My father felt in honor bound to keep the work up to the highest
standard, while the bitter jealousy and persistent enmity of certain dis-
appointed candidates for the office he held left him no repose of mind or
body. The outbreak of the war was a terrible blow to the progress of
science, and for a time he was almost hopeless about the condition of
the Observatory. Money was scarce, and as none knew what a day might
bring forth, donations toward astronomy were, of course, more scanty
than ever. Still there were generous friends who gave ungrudgingly.
Among them I should specially mention J. Ingersoll Bowditch, the loyal,
liberal-minded friend of father and son, Hon. Josiah Quincy, Robert
Treat Paine, and a few others . . .
Of his own time, strength, and energy, my father gave without stint . . .
When again and again warned by friends that fatal disease was approach-
ing or rather advancing with hasty steps, and that the only remedy
was rest, his answer was, "That is the only remedy I cannot use; I have
a work to do and must do it if I can, whether I am to live or die." . . .
No doubt his life was shortened by the privations and exposure forced
upon him by the state of the country. The Observatory was not properly
heated, and the rooms he was obliged to visit were often bitterly cold
and draughty . . .
Before his illness he travelled much among the White Mountains,
visiting wild, unfrequented spots. He made maps of the region, which
228 THE BONDS
until recently were the standard authority for all the guide books of that
section . . .
In person he was rather tall (a little under six feet) and slender, becom-
ing of later years, painfully thin. His hair was wavy and very dark, if
not black; his complexion pale, and his eyes of the deepest blue ... He
was most anxious to live to complete his work on the Nebula of Orion,
being unwilling that it should be published in an unfinished form, without
his own supervision. He worked upon it after he was too feeble to hold
a pen, until the day before his death.
Professor Asaph Hall, for many years a leading member
of the Naval Observatory at Washington and the discoverer of
the satellites of Mars, was an assistant at the Harvard Observa-
tory during the years 1857 to 1862. He was engaged as
an assistant by W. C. Bond at a salary which, although extremely
small, made it an inducement for him to come to Cambridge.
The opportunities for mathematical studies at the University
and for practical observation at the Observatory were the
special attractions. Some extracts from a statement by him
of his experiences during those years throw interesting light
on the Bonds, and incidentally on Mr. Hall himself and the
struggles of a poor but ambitious young astronomer of that
day. The statement was written in 1895, at the request of
Mr. Bond's daughter. 6
My wife and I reached Cambridge in the last part of August, 1857. We
had a kind reception from Professor W. C. Bond. Professor G. P. Bond
was absent on a visit to New Hampshire. I was set to work making
observations for time, to read the chronograph sheets, to work out the
instrumental constants, and to compare and rate the chronometers.
Professor Bond was very kind and pleasant, so that under his guidance
I made good progress. I worked hard and spent most of my time at the
Observatory. After a month or six weeks Professor G. P. Bond returned.
He seemed a little surprised to find an assistant in the observatory, and
doing so much work. He had a free talk with me, and found out that
I had a wife, twenty-five dollars in cash, and a salary of three dollars a
week. He told me very frankly that he thought I had better quit astron-
omy, for he felt sure I would starve. I laughed at this, and told him my
wife and I had made up our minds that we were used to sailing close to
the wind, and felt sure we would pull through. He appeared satisfied.
Op.cit., 77, 1897-
GEORGE PHILLIPS BOND 229
Afterward I worked a great deal with him as an assistant for recording
and reducing his observations.
Professor W. C. Bond was in poor health when I entered the observa-
tory, and died early in 1859 . . .
Professor George P. Bond succeeded his father as director. He was
very active during my stay at the observatory in making experiments
and observations in photographing the stars, in photometric observations,
and in his work on the nebula in Orion. His work on the Comet of
Donati, in 18587 was a very complete investigation of the physical appear-
ances of that great comet. I assisted Professor Bond in all this work
and in the reductions, besides pushing on my own studies. I have a
very distinct recollection of how cold my feet were when he was making
his winter observations on Orion. I sat in the small alcove of the great
dome behind a black curtain and noted on the chronometer the transits
of stars when Professor Bond called them out, and wrote down the readings
for declination. For some of the brighter stars which were observed on
the chronograph I had to note the click of the key, and my record was
compared with that of the chronograph down stairs. I became so expert
that the difference rarely exceeded a tenth of a second, and for the fainter
stars the chronograph was not used. Sometimes I was called to the
telescope to examine a very faint star, or some configuration of the
nebula. Professor Bond had one of the keenest eyes I have ever met
with. His work on this great nebula forms an epoch in its history . . .
Professor Bond indulged great hopes that photography would render
much aid in the measurement of double stars and clusters.
Professor George P. Bond had received, evidently, a much more
complete training than his father. While he had not that familiar knowl-
edge of mathematical formulas which distinguishes the professional
mathematician, he had what is better: He was thoughtful and ingenious
in his investigations. He liked to study things in their actual relations,
and had the spirit of an inventor. His style of mind led him to original
work. He was the first to apply the method of mechanical quadratures
directly to the rectangular equations of motion, a method afterward
discovered and elaborated by Encke. He was among the first to take
up photography and carry it out to practical results. His ability has
not, I think, been sufficiently recognized; but he was a shy and reserved
man, made so, perhaps, by the condition of his health.
Although I was poor and worked hard, I was not sick a single day
during those five years at Cambridge. They are for me a pleasant
remembrance of hope and struggle, and I was fortunate L; having to deal
with two such honorable men as the Bonds."
7 H. A., 3i 1862.
230 THE BONDS
On the death of William Cranch Bond, the question of his
successor became at once urgent. George P. Bond was
not the only candidate. Professor Benjamin Peirce was
among the aspirants. His high talents in mathematical
and astronomical research made him one of the foremost
figures in American scientific circles. Nevertheless, the Cor-
poration selected Bond, and the choice was evidently a wise
one. The Observatory had already made for itself an enviable
reputation, chiefly by work of a high order on observational
lines, and Bond had been intimately associated with his
father in much of this. The discovery of Bond's Dusky Ring
of Saturn and the eighth moon was as much his work as that
of his father. Professor Peirce was not an observer. At that
time, especially, observations of the best class were the chief
duty of the director as well as of the staff. Bond's abilities
in this line were unequalled in America and unsurpassed any-
where. Also, as stated elsewhere, his mathematical ability
was more than ordinary, and his originality, energy, and
devotion to his work were above praise. Also he was thor-
oughly familiar with the work and needs of the Observatory.
Professor Peirce, however, was deeply offended by Bond's
selection, and an estrangement which embittered Bond's career
occurred between them. An unfortunate and unfair antagonism
was shown by Professor Peirce and a few other scientific men
who sympathized with him. Bond attempted to heal the
matter by writing a conciliatory letter to Mr. Peirce, but
received no reply.
Once aroused by what appeared to him an injustice, Bond
was capable of assuming a determined, and possibly somewhat
obstinate stand. Like his father, he could not be driven by
adverse criticism which appeared unjust to him, but on the
contrary was impelled to more determined action. This is
shown by the intense labor with which he devoted himself to his
observations of the Orion Nebula because he believed that his
father's study of it had been unduly criticized by Struve; Bond
felt a criticism of his father more intensely than one of himself.
GEORGE PHILLIPS BOND 231
Probably the work which brought Bond his greatest reputa-
tion was his monograph on the comet of Donati, the Great
Comet of 1858, which is given in full in the third volume of
the Annals of the Observatory. Holden says:
Nothing of this excellence had ever been done before; now that we have
photography to aid us, nothing of the sort will ever be done again. It
stands alone, and is and will remain unique of its class. 8
The publication of this work won general approval both at
home and abroad. The drawings of the comet reveal Bond
not only as a most exact observer, but as an artist as well.
The memoir gained him the award of its gold medal by the
Royal Astronomical Society of Great Britain, the first presen-
tation of the medal to an American astronomer. The medal
was formally awarded at the meeting of the Society in February,
1865; the formal announcement did not reach Cambridge until
a few days after Bond's death, but happily his friends in London
had informed him a few weeks earlier that the award was to
be made.
Of almost equal merit was his study, referred to above, of the
nebula in Orion. The results are given in Volume V of the
Harvard Annals. His object appears to have been twofold:
to meet the adverse criticisms occasioned by his father's early
paper on this nebula; and to leave a monograph on the subject
that should be above criticism. Bond began this investigation
in 1857, but interrupted it for the work on Donati's Comet, and
did not entirely finish it before his death. The results were
completed for publication by Professor Safford. Bond's
monograph of the nebula was later checked with the 26-inch
telescope at Washington by Professor Holden, who has
expressed enthusiastic appreciation of the accuracy and beauty
of Bond's work. In a paper published in 1880, Holden states:
"I am acquainted with but one drawing of the nebula which
is entirely above criticism that of the late G. P. Bond."
Professor Holden also checked and verified Bond's list of
noi stars in the nebula, and states that although made with a
8 Holden, op. cit., 267, 1897.
232 THE BONDS
telescope of 15 inches aperture, it contained " almost every
star visible in the much more powerful instruments used by
Lassell, Lord Rosse, and myself. " A severer test of the accu-
racy of the drawing of the nebula came with the introduction
of photography. Perhaps no drawing of such an object
before the days of photography will bear this test so well as
Bond's drawing of the Orion nebula.
In his younger years, Bond sought assiduously for comets
and independently discovered eleven, although it was found later
that most of them had been seen at an earlier date in Europe.
He computed the orbits of many comets, and published a paper
on cometary calculations. 9 He also computed the first orbit
of Hyperion, the satellite of Saturn discovered by the Bonds.
He propounded a method of mechanical quadratures, 10 later
more fully developed by Encke. He was also the author of a
paper on the use of equivalent factors in the method of least
squares. 11
The reduction of the longitude observations made for the
United States Coast Survey by exchange of chronometers
between Liverpool and Cambridge was carried on largely
under his direction. The results furnished the best deter-
minations of American longitudes made before the introduction
of the electric method.
Bond planned the first observations of the zones of faint
stars situated between the equator and i oo' of north declina-
tion, and did some of the early work. He also carried out many
able observations and fertile investigations in the photometry
of the sun, moon, planets, and stars.
Nowhere was Bond's originality so well shown as in the early
experiments in photographic methods, and especially in his
almost prophetic appreciation of the possibilities of astronomical
advancement by means of photography. Some of the achieve-
ments attained later by other investigators would in all proba-
9 Mem. Amer. Acad., New Series, 3, 97, 1848,
10 Ibid. ,4, 189, 1849.
11 Ibid., 6, 179, 1856.
GEORGE PHILLIPS BOND 233
bility have been anticipated by him, had he lived to take
advantage of the great improvements in the manufacture
of the photographic plate, especially in its sensitiveness. The
first photograph of a star was made under the direction of
the Bonds in 1850. Earlier photographs of the sun and moon
had been obtained elsewhere, but the first photographs of the
moon to attract much admiration were made at Harvard in
1849 an d the years following.
Wet plates were used in all the experiments carried out by
Whipple and Black under the direction of the Bonds. The
invention and perfection of the dry plate brought an immense
advance in photographic methods, making possible exposures
of any desired duration; but these improvements came too late
for the Bonds.
The following extracts from a letter written by George P.
Bond to Hon. William Mitchell, on July 6, 1857, show how clear
and complete was his vision of future possibilities:
About. seven years since [July 17, 1850] Mr. Whipple obtained daguer-
reotype impressions from the image of Alpha Lyrae formed in the focus of
the great equatorial, and subsequently from Castor, thus establishing a
simple, but not uninteresting fact the possibility of such an achievement.
On these occasions a long exposure of one or two minutes was required
before the plate was acted upon by the light, and in this interval the irregu-
larities of the Munich clockwork were so large as to destroy the symmetry
of the images, while the smaller stars of the second magnitude would not
"take "at all.
For some years Mr. Whipple gave his attention to photographs of the
moon and Sun, and the stars were left to themselves. But improvements
in the art progressed rapidly; the preparations were more sensitive, the
artists had acquired more experience. At the same time the principle of
the spring-governor had been thoroughly tested, and found to supply a
great desideratum in imparting a sidereal motion to the telescope incom-
parably more uniform than that attained by the Munich mechanism . . .
Messrs. Whipple and Black recommenced their trials on other images
(taken by the Collodion process) in March of the present year [1857], and
they are still in progress . . . The field for experiment is too vast to be at
once occupied, even if we were provided with unlimited means. But the
results already obtained in the disconnected attempts we have thus far
been enabled to make, are of the highest interest, and suggest possibilities
234 THE BONDS
in the future which one can scarcely trust himself to speculate upon.
Could another step in advance be taken equal to that gained since 1850,
the consequences could not fail of being of incalculable importance in
astronomy.
The same object, Alpha Lyrae, which in 1850 required 100* to impart
its image to the plate, and even then imperfectly, is now photographed
instantaneously with a symmetrical disc perfectly fit for exact microm-
eter measurement. We then were confined to a dozen or two of the
brightest stars, whereas now we take all that are visible to the naked
eye . . .
On a fine night the amount of work which can be accomplished, with
an entire exemption from the trouble, vexation and fatigue which seldom
fail to attend upon ordinary observations, is astonishing.
The plates once secured, can be laid by for future study by daylight
and at leisure ... As yet, however, we obtain images only from stars
to the sixth magnitude, inclusive. To be of essential service to astronomy,
it is indispensable that great improvements be yet made, and these, I
feel sure, will not be accomplished without a great deal of experimenting
. . . But could we but press this matter on, we should soon be able to
say what we can and what we cannot accomplish in stellar photography
the latter limits we certainly have not reached as yet . . . There is
nothing then so extravagant in predicting a future application of photo-
graphy to stellar astronomy on a most magnificent scale . . .
What more admirable method can be imagined for the study of the
orbits of the fixed stars, and for resolving the problem of their annual
parallax than this would be if we could obtain the impressions of the tele-
scopic stars to the tenth magnitude! ... It would be useless for me to
attempt to describe in a letter the processes and results in detail.
P. S. I find I have forgotten to allude to two important features in
stellar photography one is that the intensity and size of the images taken
in connection with the length of time during which the plate has been
exposed measures the relative magnitude of the Stars. The other point
is, that the measurements of distances and angles of position of the double
stars from the plates, we have ascertained by many trials on our earliest
impressions, to be as exact as the best micrometric work. Our subse-
quent pictures are much more perfect, and should do better still.
This letter deals only with the possibilities of stellar photog-
raphy. Bond, however, was equally interested in the subject
as related to the sun, moon, and other celestial objects. Holden
calls George P. Bond "the father of celestial photography."
The appellation appears just could the life of Bond have been
GEORGE PHILLIPS BOND 235
spared for 20 or 30 years, he would doubtless have taken a
dominant part in the tremendous advances made in astro-
nomical photography through the introduction of the extremely
sensitive dry plate.
Bond saw clearly the desirability of seeking a more satis-
factory site for the observational part of the observatory work.
The atmospheric conditions for refined observations were never
good at Cambridge, and have steadily deteriorated owing to
the encroachments of a large city. In a letter to J. Ingersoll
Bowditch, dated March 31, 1860, he presented the arguments
for such a plan, which for lack of funds was not possible of
execution during his lifetime. He wrote:
It would be certain to repay the outlay if an astronomer of experience,
furnished with a good telescope and photographic apparatus, should visit
different parts of the world (high table-lands and mountains), and experi-
ment on the advantages of a pure and tranquil atmosphere . . . Why
should we always have to wait for the example of the governments of
Europe in encouragement of scientific enterprises? If our observatory had
possessed the means, we should have sent off an expedition of this kind
years ago; it was actually proposed, but, of course, nothing could be
accomplished without money. 12
He even suggested that such an expedition should visit Cali-
fornia and the west coast of South America, a remarkable
proposal in view of what was really done a generation later.
Bond made two trips to Europe, during which he met nearly
all the prominent European astronomers, and was everywhere
received with distinction.
In 1856, Bond was offered the position of Chief Astronomer of
the survey of the northwest boundary between the United States
and British Columbia. The salary was about double that
which he was receiving at Cambridge, and the position would
have brought him distinction. His love of the work at Cam-
bridge, however, and especially the condition of his father's
health, induced him to decline the appointment.
Bond was a member of the American Academy of Arts and
Sciences, a corresponding member of the Royal Bavarian
12 Holden, op. cit., 182, 1897.
236 THE BONDS
Academy of Sciences, and a Foreign Associate of the Royal
Astronomical Society of Great Britain. As already stated
he was the first American to receive the gold medal of the last-
named Society. He was not chosen one of the original members
of the National Academy of Sciences, incorporated in 1863.
This was believed by his friends, probably justly, to have been
due to the enmity of the prominent men of science to whom
reference has already been made.
Bond died at less than forty years of age. If we take into
consideration his continual struggle with financial difficulties,
and, during his later years, with consumption, together with
the irritation caused by the enmity of the small clique of scien-
tists referred to above, the indomitable energy and devotion
which he displayed were heroic, and his achievements
memorable.
CHAPTER XVII
WINLOCK AND PICKERING
WITH the passing of the Bonds, a new era was approaching.
The brief directorship of Winlock may be regarded as transi-
tional. With Pickering came a period of immense develop-
ment, and the introduction on a large scale of astrophysical
problems.
Joseph Winlock, 1826 to 1875; Director, 1866 to 1875.
Joseph Winlock, third director of the Observatory, was born in
Shelby County, Kentucky, on February 6, 1826. It may be
of interest to note that the preceding director, George P.
Bond, was born in 1825, and the distinguished American
astronomer Benjamin A. Gould, in 1824.
Mr. Winlock came of a notable family. His grandfather,
Joseph Winlock, by birth a Virginian, was an officer of the
American Revolution who served under Washington and
attained the rank of captain. Later he married Miss Stephen-
son of Virginia, and they settled in Kentucky before it became
a state. In the war of 1812 he attained the rank of brigadier
general. His son, Fielding Winlock, father of the astronomer
Joseph Winlock, was a lawyer, and received a part of his legal
training in the office of Henry Clay. Fielding Winlock served
with his father in the War of 1812 and later held various posi-
tions of honor.
Joseph Winlock was graduated from Shelby College in
1845. His unusual mathematical ability must have been
evident during his undergraduate career, since at graduation
he was appointed Professor of Mathematics and Astronomy
in that institution. The opportunities for the study of astron-
omy at Shelby College must have been limited, but his devotion
237
238 WINLOCK AND PICKERING
to the science was shown by the use of his first savings to
purchase a set of the Astronomische Nachrichten. Fortu-
nately for Winlock and for astronomy, the fifth meeting of the
American Association for the Advancement of Science (founded
in 1847) was h e ld in Cincinnati in May, 1851. Winlock was
present at the meeting, and met Benjamin Peirce, Perkins
Professor of Mathematics and Astronomy at Harvard Uni-
versity. At this time Peirce was the most famous American
mathematician, and his abstruse mathematical treatises were
familiar to Winlock.
As a result of his acquaintance with Peirce, Winlock went
to Cambridge in the following year, 1852, to take part in the
work of the newly established office of the American Ephemeris
and Nautical Almanac. This department had been authorized
by act of Congress in 1849. It was placed under the super-
intendency of a naval officer, Lieutenant C. H. Davis, but the
responsibility for all the mathematical formulae and com-
putations was intrusted to Professor Peirce. On this account,
and in order to make use of the library and other advantages
of Harvard University, the headquarters of the Ephemeris
were located in Cambridge until they were removed to Washing-
ton in 1866. The first volume of the Ephemeris, for 1855,
was issued in 1852.
On his arrival in Cambridge, Winlock joined the able corps
of computers attached to this service, which successfully
established the reputation of the American Ephemeris under
the direction of Professor Peirce. Among these computers were
Simon Newcomb, Truman H. Safford, John D. Runkle,
William Ferrel, Maria Mitchell, and others well known in
later years.
Winlock remained in Cambridge until 1857, when he was
appointed Professor of Mathematics in the United States
Naval Observatory at Washington. He resigned this position
soon after to accept the superintendency of the American
Ephemeris and Nautical Almanac, and returned to Cambridge.
His name appears as Superintendent in the volumes of the
JOSEPH WINLOCK 239
Ephemeris for the years 1860 and 1861, published in 1858 and
1859. I n I ^S9> Professor Winlock was chosen to take charge of
the mathematical department of the United States Naval Acad-
emy, and moved to Annapolis. The Naval Academy was later
removed to Newport, on account of the Civil War, and at that
time Mr. Winlock was again made Superintendent of the Ameri-
can Ephemeris, and returned to Cambridge. His name again
appears as Superintendent in the volumes for the years 1864 to
1867, published during the years 1862 to 1865.
Until his appointment as director of the Harvard Observatory,
Winlock had devoted his life chiefly to the study, teaching, and
development of mathematics. His chief acquaintance with
astronomical instruments appears to have been with an excellent
telescope of 7^ inches aperture, the property of Shelby College.
When he was appointed an assistant at the Cambridge office
of the American Ephemeris and Nautical Almanac, Winlock
borrowed the telescope from his old college and had it mounted
in Cambridge.
In the University of Missouri Catalogue for 1884 to 1885,
the following description of the Shelby telescope is given :
This telescope was ordered in 1848 from the establishment of Merz &
Mahler, 1 of Munich, for the use of Shelby College, Shelbyville, Kentucky.
It was received at Shelbyville in November, 1850, and cost, when mounted,
$4,000. It was mounted under the direction of Prof. Joseph Winlock, and
used by him when he was a professor in that institution. After Prof.
Winlock went to Cambridge, Mass., he borrowed this telescope, and, in
connection with Dr. B. A. Gould, established there the Cloverdon Observa-
tory. In Loomis's Recent Progress of Astronomy, the following statement
is made respecting this instrument, which was then the fourth in magni-
tude in the United States:
"The great telescope belonging to Shelby College was loaned to Prof.
Joseph Winlock, and was removed to Cambridge, Massachusetts, where
temporary accommodations were provided for it, and this establishment
is known by the name of Cloverdon Observatory." . . . "Numerous
observations on comets, and on some of the newly-discovered planets,
1 In the Report of the Director of the Laws Observatory, March, 1903, Scares
pointed out that the telescope bears the inscription: " Merz u. Sohne in Miinchen."
240 WINLOCK AND PICKERING
have been made with this telescope by Dr. B. A. Gould and Prof. Joseph
Winlock, some of which have been published in Gould's Astronomical
Journal. This great telescope has recently been returned to Shelby
College/'
It is of interest that this was also the first instrument ever used
by Dr. Harlow Shapley, the present Director of the Harvard
Observatory. The telescope was purchased by the University
of Missouri, and installed as the principal equipment of the
Laws Observatory.
In February 1866, without any solicitation on his part,
Winlock was chosen Director of the Astronomical Observatory
of Harvard College, and at the same time was made Phillips
Professor of Astronomy. Later he was also given the title of
Professor of Geodesy.
On assuming the directorship he evinced a rare talent in
mechanical construction and invention. During the nine
years of his supervision he devoted himself with enthusiasm
not only to the improvement of the existing equipment, but
also to the acquisition of new instruments.
The large 1 5-inch refractor, the glory of the early days
of the Observatory, no longer played the role which it held
under the Bonds. Under those able observers it had brought
much prestige to the institution, but the age of great discoveries
by visual means was passing. Under the direction of Winlock,
the telescope was used chiefly for observations of double stars.
A large number of miscellaneous spectroscopic observations of
stars, nebulae, and comets were also made. Of special interest
was a spectroscopic research on the aurora, by C. S. Peirce.
The instrument was also used by N. S. Shaler, E. L. Trouvelot,
and others, for special studies.
Under the Bonds, the large refractor had been used in part
for the determination of the positions of stars, especially in
the zone between declination oo' and +io'. Mr. Winlock
decided to discontinue the use of the large equatorial for such
observations, and to employ a new and larger meridian
instrument.
JOSEPH WINLOCK 241
The meridian circle already in use had never been satisfactory
for the determination of declinations. Winlock impressed
upon the friends of the Observatory the need of a new meridian
circle, and twelve thousand dollars were promptly subscribed
for this purpose. The director then spent four months in Eu-
rope visiting the principal observatories, and making himself
familiar with the latest improvements in meridian instruments.
In the new instrument, made by Troughton and Simms of Lon-
don, were incorporated certain improvements suggested by Mr.
Winlock, as described in Chapter IV. Observations were begun
with this instrument in 1871. It was used for many years in
work on the positions of stars, at first by Professor W. A.
Rogers and later by Professor Arthur Searle.
Winlock took part in two expeditions to observe total
eclipses of the sun. In 1869, he was requested by Professor
Peirce, at that time Superintendent of the United States Coast
Survey, to go to Kentucky at the head of a party whose duty
it should be to cooperate with officers of the Survey in the
observation of the total solar eclipse of August 7. Mr. Win-
lock gave special attention to spectroscopic and photographic
observations, then in their infancy. Several new and effective
mechanical devices were introduced by him.
Winlock also had charge of the party sent to Spain to observe
the eclipse of December 22, 1870. He prepared for this
expedition a lens of 32}^ feet focal length, mounted in a horizon-
tal position. The image of the sun was thrown upon the lens
by means of a heliostat. By this device the necessity of using
an enlarging lens was avoided. The success of these observa-
tions and the convenience of the method caused its wide
adoption by other astronomers. Beginning in July, 1870,
similar apparatus was in use for some time at the Harvard
Observatory for daily observations of the solar surface.
During Winlock's administration the time service was much
improved and extended. The regular transmission of time
signals to Boston was begun in 1872, and the service was made
to yield a moderate financial return. The installation and
242 WINLOCK AND PICKERING
maintenance of this service, however, was a severe tax on the
time and energy of the small staff of the Observatory.
Winlock took a loyal and unselfish interest in the unpublished
work of his predecessors. A considerable part of his time was
spent in the reduction and preparation for the printer of the
unpublished observations made during the administration of the
Bonds.
Professor Winlock's personal characteristics were such as
to command not only the respect but also the affection of
those with whom he was intimately associated. Among
strangers he was singularly reticent, and even with his friends
his words were often as brief as circumstances permitted. He
had, however, a quiet sense of humor.
Newcomb, in his Reminiscences, relates the following story,
which in a slightly different form was current at the Observa-
tory. Mr. Winlock was introduced to a lady. They regarded
each other for a decorous interval, but neither said a word.
Later Mr. Winlock was asked, "Why did you not talk to
the lady?" He replied, "I had no statement to make to
her."
Mr. Hilgard, when in charge of the Coast Survey, was
impressed by the terseness of the communications he received
from Mr. Winlock and resolved to rival them. A child had
been born in the family of each. Hilgard addressed a com-
munication to Winlock in these words : " Mine's a boy. What's
yours?" The reply was: "Dear Hilgard; Boy. Yours, etc.
J. Winlock."
Among friends Mr. Winlock was genial and, on rare occa-
sions, even talkative. In his administrative capacity, which
was tested in various positions during his life, Winlock dis-
played to his associates and assistants unusual disinterestedness,
keen appreciation, and a delightfully serene nature.
His leadership was nowhere asserted but everywhere acknowledged.
A man of few words but of much thought, of no pretensions but of great
performance, he did his own part patiently and well, and by his example
inspired others to do theirs.
>^m
PLATE XXI. JOSEPH WINLOCK.
(Facing page 242)
PLATK XXII. EDWARD C. PICKERING.
EDWARD CHARLES PICKERING 243
Professor Winlock's work as director was chiefly adminis-
trative. His own observations were comparatively few, but
much was accomplished under his direction. He wrote almost
as sparingly as he spoke. No one questioned, however, his
thorough knowledge of all the technicalities and principles
involved in the different instruments and investigations.
His brief directorship was largely absorbed in a disinterested
effort to perfect and increase the equipment of the Observatory.
In addition to the new large meridian circle, to which reference
has already been made, many other new instruments were
acquired. These included a Clark refractor, clocks and chro-
nometers, a Russian Transit made in the workshop of the
Poulkova Observatory, a Zollner astrophotometer, and various
spectroscopes and meteorological instruments.
In the midst of such activities, when the material equipment
of the Observatory had been brought to a satisfactory condition
and a long period of useful service seemed to open to him,
Winlock died suddenly and unexpectedly at the age of forty
nine years.
Edward Charles Pickering, 1846 to 1919; Director, 1877 to
1919. Edward Charles Pickering was born on Beacon Hill,
Boston, July 19, 1846. He died at Cambridge on February 3,
1919. At the time of his death the Observatory was less than
eighty years old, and he had been Director 42 years, a period
considerably longer than the combined terms of his three
predecessors.
Mr. Pickering was fortunate in his heritage. Of a family
always prominent in New England history, he was heir neither
to riches nor poverty, but to splendid opportunity, which he
eagerly grasped. From early youth to old age, his zeal in the
pursuit of scientific problems was unbounded. His education
was begun in private schools, but later carried forward at the
Boston Latin School. He had small love of the classics and
gave them scant attention. In the Lawrence Scientific School,
however, he entered upon his work with that enthusiasm which
244 WINLOCK AND PICKERING
marked all the activities of his mature life. He was graduated
from this school summa cum laude at the age of nineteen, and
was immediately appointed Instructor in Mathematics in
that institution. A year later he became Assistant in Physics
at the Massachusetts Institute of Technology, and in the
following year Thayer Professor of Physics, a position which
he held until be became Director of the Observatory. During
his ten years at the Institute, the history of his work is the
history of the Department of Physics. His appointment as
Thayer Professor came at the urgent request of President
William B. Rogers, the former occupant of the chair, who wrote
to Pickering regarding it :
Let me say that, with all the urgency of other Institute duties, I should
be quite unwilling to relinquish it to any other successor, so much do I
love its exercises, and so sure am I that under your direction they will
preserve the breadth and practical character which it has been my aim to
give them.
At this time Pickering was only twenty two years of age.
During the busy years of his professorhip at the Institute,
41 scientific papers were published by him (or by students under
his direction) as well as two volumes of his pioneer textbook
entitled Physical Manipulations. He established in connection
with these volumes the first physical laboratory in America for
students. The idea of such a laboratory had been suggested
by President Rogers but its successful installation and manage-
ment were due to Pickering. The importance of this develop-
ment was widely recognized; it has been regarded as marking
an epoch in the teaching of physics. Pickering measured
the value of the course in physical manipulation by its success
in teaching the student to think for himself, and in fitting him
to solve problems experimentally. Research was Pickering's
chief interest, although teaching consumed the greater part of
his time. His own investigations, on the subject of light,
formed a fitting foundation for his future life work.
In 1869 and 1870, Mr. Pickering took part in the expeditions
sent out by the United States Government to observe the total
EDWARD CHARLES PICKERING 245
solar eclipses. He introduced at the Institute a course of
lectures for older students on geodesy and topography, and
one on practical astronomy, especially for engineers. He also
designed a spectrometer, which was constructed by Alvan
Clark and Sons, and was the most powerful instrument of its
kind at that time.
A notable contribution of a different character was made
by his early experiments with the telephone. In 1870 he con-
structed a receiver consisting of a flexible iron diaphragm
supported at the edges and replacing the armature of an
electromagnet. The apparatus appears to differ in no way
in principle from the receiver later in use. He would not
consider protecting the device by patent, since such a course
would have been contrary to his code of ethics.
In 1876 Pickering founded and became first president of
the Appalachian Mountain Club. The great value of this
club for popular purposes is well known, but his primary aim
was the furthering of health and science. He perfected a
portable 1 2-pound micrometer level for the rapid determination
of approximate positions and altitudes. With this instrument
he made thousands of observations of various points of interest
in the White Mountains. The intensity of his interest and the
enthusiasm and success with which he carried out his plans
made a deep impression on his associates.
Professor Pickering was chosen Director of the Harvard
Observatory in 1876, and entered upon his duties on February
i, 1877. The appointment of a physicist to direct an astrono-
mical observatory caused some criticism from astronomers
of the old school. There was no lack of candidates for the
position among astronomers of experience and reputation.
President Eliot, however, who called him to the directorship
of the Observatory, was thoroughly familiar with the unusual
scientific and administrative ability which Pickering had shown
at the Massachusetts Institute of Technology.
Pickering found the times propitious for the introduction
of new methods. The old astronomy of position and motion
246 WINLOCK AND PICKERING
which had occupied the chief place in the programs of the great
observatories in the past was destined soon to be pushed into
the background by the urgency of astrophysical problems.
Even the determination of magnitudes of stars had not been
placed on a sound scientific basis, and comparatively little was
known as to their nature. Everywhere there was a great dearth
of facts. In such a condition of the science, Pickering decided
that the accumulation of great masses of data would constitute
the greatest contribution he could make to the advancement
of astronomy. Theories in regard to the structure of the stellar
universe could wisely be deferred until better foundations
were provided.
At first the range of his researches was sharply limited by
the equipment and resources of the Observatory. There were
two instruments of great power and high quality for that day,
the i5-inch refractor and the 8-inch meridian circle. The
financial resources were insufficient to keep these actively
employed and to publish the results. Pickering's first care
was to secure additional funds for this purpose and also for the
extension of his investigations into new fields. His first
Annual Report contained an appeal for financial aid, and every
succeeding report included some such direct or indirect appeal.
The great schemes he was planning could be carried out only
through the assistance of many minds and many hands, and
these could be obtained only by a great increase of endowment.
Little by little this was secured. His own part in this increase
was considerable. In all, he gave to the Observatory more than
a hundred thousand dollars.
The first and one of the greatest of his achievements was
in stellar photometry. For a while, for lack of suitable instru-
ments, he carried on investigations with photometers attached to
the large refractor. These labors held particular interest because
of the measurement, in 1877, of the newly discovered satellites
of Mars. While he was engaged in carrying on these investiga-
tions, a meridian photometer was constructed for the convenient
measurement of the magnitudes of all the brighter stars.
EDWARD CHARLES PICKERING 247
The improvement of the photographic dry plate came at
the beginning of Pickering's administration, and its possibilities
were promptly grasped by him. Something of romance
was perhaps lost by the introduction of photographic methods,
but the gain in efficiency was tremendous. Charting a field
of stars, formerly a labor of weeks or months, could be accom-
plished in an hour, the resulting photograph often showing more
stars than could be seen by the eye with a telescope of equal
size.
Pickering early saw the possibility of photographic photo-
metry and made many experiments and observations. For
many years the difficulties were too great for its successful
use, but before the close of his life these had been overcome
in large part. He conceived the idea that a large collection
of celestial photographs, covering the whole sky and repeated
at short intervals over a long series of years, would have
immense value, and he attempted to make this record of the
stars as complete as possible. An auxiliary station was
founded in the southern hemisphere in order to cover the whole
sky. Photographs of various kinds were taken, especially
charts, and the spectra of the stars were obtained with the
objective prism. Records were made with instruments of
widely different powers: at one extreme the 24-inch Bruce
doublet, which, with an exposure of one hour showed stars
to about the seventeenth magnitude; and at the other extreme,
a wide-angled one-half inch Ross-Zeiss lens covering a field
about 60 degrees square, so that the entire sky available could
be covered in a single night with exposures of one hour, stars
to about the ninth magnitude being photographed.
The extensive discoveries of novae, asteroids, variable stars,
and other interesting celestial objects from this collection of
photographs are ample proof of its value. A series of plates
having exposures of four hours with the 24-inch Bruce was
proposed, and a considerable number of excellent photographs
were made at Arequipa from the South Pole northward. Such
a series, if it could be completed for the whole sky, would
248 WINLOCK AND PICKERING
contain a hundred million or more stars, and from it might be
derived definitive lists of clusters and nebulae for the determina-
tion of their distribution, motions, and distances. The scheme,
however, would require a long time for its completion with a
single telescope, and meanwhile the Selected Areas of Kapteyn,
Pickering's own Standard Regions, and other cooperative
plans made this complete plan less necessary.
The study of stellar spectra, carried on by several observers
under Pickering's direction, constitutes one of the greatest
achievements of the Observatory. The completion of the
Henry Draper Catalogue, giving the spectral classification of
more than two hundred thousand stars, formed a fitting close to
Pickering's career. To estimate its importance, one needs only
to remember how small was our knowledge of the nature of the
stars in 1885, when he began to photograph them with the
objective prism, and to consider how intimately the Harvard
classification has entered into nearly all lines of astronomical
research.
Aside from the classification of spectra, the objective prism
plates yielded enough in the way of by-products to justify
Pickering's enthusiasm: several novae, hundreds of new variable
stars, and long lists of peculiar stars of special interest. Noth-
ing pleased him more than to know that the results obtained
at the Observatory were those most needed by astronomers
in their investigations. Certainly no better example could be
found of a recognized and fulfilled astronomical need than
the classification of stellar spectra in the nine volumes of the
Henry Draper Catalogue, as carried out by Miss Cannon.
His conception of a vast collection of photographs of the
stars, destined in time to give a history of the sky, was unique.
Its execution was carried forward with zeal and success. These
half -examined plates, made, in many cases, only for the purpose
of securing as complete a record as possible, appeared to many
as unnecessary and extravagant, and even excited ridicule.
This seems absurd now that their value has been so fully
demonstrated. Hardly a new star or variable has been
EDWARD CHARLES PICKERING 249
discovered in recent years whose history could not be traced
in a large degree upon these photographs. The study of the
minor planet Eros as described in Chapter VII furnished an
early example of their value. Although so long in use, this
collection still exists, growing more valuable with lapse of time.
Constant additions are being made to it under the direction of
Dr. Shapley.
It is possible that Pickering's best work was in photometry
and spectroscopy, but he was active in many other fields.
The study of variable stars was a marked feature of the Observa-
tory work during his administration. When he began his
observations, about 200 variables were known; at the time of
his death, 3435 variables had been found at the Harvard
Observatory. He published, in 1880, a classification of variable
stars which is the accepted notation at the present time. He
soon began to encourage their observation on a scale hitherto
unknown. This was possible not only through the increasing
resources of the Observatory, but also through the assistance
of amateurs. When the American Association of Variable
Star Observers was formed, he gave the members the assistance
which they needed. The spirit in which this was given and
received is well shown by the regard and affection in which he
was held by the members of the Association. At their meeting
in 1918, they presented him with a beautiful gift, after their
president had made the following reference to him : He has as-
sisted us in everything that we have undertaken and has care-
fully watched our progress along every step of the way, and
the manner of his so doing has been that of the Big Brother.
The astronomy of position was not neglected during Picker-
ing's directorship, although his chief interests lay in astro-
physical lines. Two zones of the Astronomische Gesellschaft,
those from +49 55' to +55 10', and from 9 50' to 14 10'
declination, were observed and published during that time,
although the observations for the former zone were begun
under Professor Winlock. Altogether, the work of the meridian
circle occupied the time of one professor and several assistants
250 WINLOCK AND PICKERING
during half a century, the results filling a dozen volumes of the
Annals.
When Pickering came to the Observatory, only a dozen
volumes of the Annals had been published or were ready for
printing. At the time of his death, about 80 of these quarto
volumes had been issued or were practically ready for the
printer. Many of these, indeed, were chiefly the work of others,
supervised or edited by him. On the other hand, an enormous
amount was his own. He was a natural leader, but he was an
indefatigable worker as well. He worked for the real love of
it, carrying on observations for several hours each clear night,
in addition to his arduous duties as director. Of the two million
observations concerned in the visual Harvard Photometry,
more than half were made by him.
Pickering's interest in the work of others seemed as intense
as that in his own. His desire was to secure the largest possible
results. If he was fond of quantity, the care with which he
examined and reexamined all that he did is evidence that
quantity was not sought at the expense of quality. Loyalty
to his predecessors in office was one of his marked characteristics.
He devoted much time and badly needed financial resources,
during the early years of his directorship, toward completing
and publishing their unfinished work.
As unusual as were Pickering's scientific accomplishments,
his personal qualifications were equally rare. For men and
women he had an equal charm. His grace of manner and
conversation captivated all those who knew him intimately.
To all who seemed to have any claim upon him, he gave a
courteous regard. He seemed always able to draw out a per-
son's best qualities, and to leave him with the rare and happy
sense of having found at last real appreciation. To astronomers
especially he was ready with unlimited service, and he is
remembered by many as an ideal host.
Pickering thoroughly believed in the advantage of broad
associations for the good of science and mankind. One of the
most cherished objects of his life was to secure an international
EDWARD CHARLES PICKERING 251
fund for the benefit of astronomers of all nations. Of a similar
nature was his plan for an international southern telescope
which would be devoted to the needs of astronomers anywhere.
Believing that the best service he could render to astronomy
was the accumulation of facts, to this end he massed all the
forces he could command, instituting great pieces of research,
sometimes employing many routine workers, that in the end
a sufficient basis should be provided for a solution of stellar
problems. His practical nature led him to adopt graphical
instead of analytical methods, whenever they appeared equally
accurate.
Pickering loved to discuss but refused to dispute. He loved
appreciation, but was not swerved from an approved course
by its absence. His persistence in what he believed right was
balanced by a readiness to accept new ideas. Until the very
end of his life he kept an alert, unprejudiced mind, and was
always glad to modify or abandon his plans if something better
presented itself. He was prompt to give advice, whenever it
was requested, and possibly in some cases where it was not
desired. Always glad for friendly suggestions himself, he did
not hesitate to offer them to others. He was held in high esteem
by his fellow astronomers. The following tribute (1919) is
from one of them:
His wonderful energy and enthusiasn, his alertness, his unvarying
courtesy, his wide vision and generous heart, make his passing a keen
personal loss even to those of us who knew him slightly. For a number
of years I have thought of him as the Dean of American Science.
Mr. Pickering was married in 1874 to Lizzie Wadsworth
Sparks, daughter of Jared Sparks, a former President of
Harvard University and a well-known historian. Mrs. Picker-
ing, who is still remembered as an especially charming hostess,
died in 1906. No children were born to them.
Pickering received nearly all the honors which the world
had to bestow on a scientific man. These he valued highly
as the expression of the appreciation in which his work was
held. He received the honorary degree of Doctor from six
252 WINLOCK AND PICKERING
American and two foreign universities. He took special
pride in being a Knight of the Ordre Pour la Merite. His
collection of medals was a large one; he was twice awarded
the gold medal of the Royal Astronomical Society. In addition
to membership in American societies, he was a member or
associate of the national societies of England, Germany,
Ireland, Italy, Russia, Sweden, and Mexico. He was made a
member of the American Academy of Arts and Sciences at
the age of twenty one, and a member of the National Academy
of Sciences at the age of twenty seven. He was President of
the American Astronomical Society from its foundation in
1903 until his death in 1919.
CHAPTER XVIII
LEADING MEMBERS OF THE OBSERVATORY STAFF
MANY individuals have taken part in the investigations
of the Observatory, as shown by the list of members of the
staff given in Chapter XX. The work of a number of these was
of sufficient originality and importance to merit special con-
sideration of the authors. A few are mentioned not especially
for the quality of their work as assistants at the Harvard
Observatory, but for the scientific eminence which they later
attained elsewhere. The Observatory takes pride in their
temporary association with it. Sketches are not given here
for any member of the staff who was living at the end of 1927.
Charles Wesley Tuttle, 1825? to 1881; Staff Member, 1850/0
1854. Charles Wesley Tuttle was one of the earliest assistants
of the Observatory, under the directorship of W. C. Bond.
He took part in the observation of the stars in the zone from
the equator to o 20' north declination. This work was done,
according to the title page of Volume i, Part 2, of the Annals,
by George Phillips Bond, A.M., First Assistant, and Charles
Wesley Tuttle, A.M., Second Assistant. Tuttle also took part
in the observations of Saturn, under the direction of W. C.
Bond, the results of which were published in Volume 2, Part
i, of the Annals. He resigned his position in the Observatory
in 1854, since his eyesight did not permit him to pursue regular
observations longer. Later he took up the study of law, but
for several years at least he retained his interest in astronomy,
computing the orbits of comets. Tuttle received the honorary
degree of A.M. from Harvard University in 1854, and Ph.D.
from Dartmouth in 1880.
Horace Parnell Tuttle (brother of C. W. Tuttle?), an assistant
from 1858 to 1862, was especially devoted to the discovery of
253
254 LEADING MEMBERS OF THE OBSERVATORY STAFF
comets and the computation of their orbits. He resigned in
1862 in order to enter the Army. Later he resided in George-
town, D. C., and in Washington. He received an honorary
A.M. from Dartmouth in 1866 and from Harvard in 1868.
Etienne Leopold Trouvelot } 1827 to 1895; Staff Member,
1872 to 1874. Trouvelot was a Frenchman who resided for
many years in the United States, for a time in Medford and
later in Cambridge. He was engaged by Professor Winlock
to make drawings of various celestial objects during the years
1872 to 1874. He also had a small private observatory in
Cambridge. While residing in Medford he began a series of
observations of the sun's surface which was greatly extended
during his stay at the Harvard Observatory. Nearly a
thousand such drawings are in the possession of the Observa-
tory. Trouvelot made beautiful drawings of various other
celestial objects, including total eclipses of the sun, the surface
of the moon, planets, comets, and nebulae. These drawings
show a rare artistic ability. So far as published by the Observa-
tory, they appear in the Annals, Volume 8, Part 2.
Trouvelot was also interested in physical investigations
and in zoology. During some experiments on which he was
engaged at Medford, several specimens of the gypsy moth
accidentally escaped and caused an immense injury to plant
life, a source of deep regret to him. Trouvelot wrote many
scientific papers, chiefly on astronomical subjects, which were
published in various scientific journals, in France and the
United States.
Asaph Hall, 1829 to 1907; Staff Member, 1857 to 1862.
Professor Hall's childhood and early manhood were passed
amid the difficulties which accompany poverty. His father
died when he was thirteen. Hall was the eldest of six children,
and for many years had to assist his mother, who had been
left in straitened circumstances. At sixteen he was apprenticed
to a carpenter for three years. After he was twenty one he
began to save money with which to obtain an education. At
twenty five he started a course at Central College, McGrawville,
WILLIAM AUGUSTUS ROGERS 255
New York, attracted by the low costs and the opportunity
to pay his way by manual labor. He was dissatisfied with
the college and remained little more than a year; but he became
engaged to Miss Stickney, a pupil and instructor at the college.
They were married in Wisconsin in 1856. In the same year he
entered the University at Ann Arbor, where he remained only
long enough to become familiar with the manipulation of
astronomical instruments through the instruction of Briinnow.
After a brief experience in teaching he and his wife came to
Cambridge and he became an assistant at the Harvard Observa-
tory. His salary at first was $3 a week. Later it was advanced
to $400 a year. Hall's spare time was spent in the study of
mathematics, astronomy, and languages. As a paid assistant
his work at the Observatory was chiefly of a routine nature.
In 1862 he received an appointment as Aide at the U. S. Naval
Observatory, and, in 1863 became Professor of Mathematics in
the Navy. His greatest achievement perhaps was the discovery
of the two moons of Mars.
Professor Hall was an assiduous observer, a deep student,
and a prolific writer. The mere titles of his different papers,
problems proposed, and observations made, with the briefest
outline of their nature, would fill some thirty pages of the size
used in this volume. He received the gold medal of the Royal
Astronomical Society, the Lalande prize, the Arago medal of
the French Academy of Sciences, and was made a Knight of the
Legion of Honor. He was a member of the more important
scientific societies, both at home and abroad. He received
honorary degrees from many universities, including that of
LL.D. from Yale and Harvard. At the legal age of sixty two
Hall was retired from his professorship in the Navy; a little
later he became a lecturer on celestial mechanics at Harvard
University. The last few years of his life were passed at his
country home in the town of his birth, Goshen, Connecticut.
William Augustus Rogers, 1832 to 1898; Stajf Member, 1870
to 1886. Professor Rogers was born at Waterford, Connect-
icut, November 13, 1832, and died at Waterville, Maine,
256 LEADING MEMBERS OF THE OBSERVATORY STAFF
on March i, 1898. He graduated from Brown University in
1857, and for the next 13 years passed the greater part of the
time at Alfred University as Professor of Mathematics and
Astronomy. During this period, however, he spent a year
at the Sheffield Scientific School of Yale University as a student
of mechanics, and a year at the Harvard Observatory in the
study of astronomy under Professor Bond.
He became a regular assistant at the Observatory in 1870,
and was soon placed in charge of the new meridian circle
by Professor Winlock. His chief work with this instrument
was the observation of the zone of stars from 49 50' to 55 10'
north declination.
Rogers became Assistant Professor of Astronomy in 1877, and
held that position until he accepted a professorship of Physics
and Astronomy at Colby College in 1886.
Rogers was also interested in the standards of length, tem-
peratures, and other physical constants, and wrote many
papers on these subjects. He was sent to Europe in 1879 by
the American Academy of Arts and Sciences to obtain copies
of the imperial yard and the metre des archives. The copies
were widely employed in the United States and Canada.
Rogers was a Fellow of the Royal Society of England, and
later an Honorary Fellow of that body; Honorary Fellow of
the Royal Microscopic Society; Fellow of the American Associa-
tion for the Advancement of Science, twice president of Section
A, and once of Section B ; member of the American Academy
of Arts and Sciences, and of the National Academy of Sciences.
He received the honorary degrees of A.M., Ph.D., andLL.D.
from Yale, Alfred, and Brown Universities, respectively.
Rogers took a keen interest in civic and religious activities.
A kind and generous nature endeared him to his associates.
Samuel Pierpont Langley, 1834 to 1906; Staff Member,
1865 to 1866. Langley, one of America's most distinguished
men of science, was born in Boston, August 22, 1834, and died
in Washington, February 27, 1906. He was graduated from
the Boston High School in 1851, and took up the study of
TRUMAN HENRY SAFFORD 257
engineering and architecture which he followed until 1864.
In that year and the following he travelled in Europe visiting
the principal observatories. On his return in 1865, he became
an assistant in the Harvard Observatory, remaining until he
received, in 1866, an appointment as Assistant Professor of
Mathematics at the United States Naval Observatory. Sub-
sequently he became Director of the Allegheny Observatory,
where he remained 20 years. Langley was a remarkable
observer, as is shown by his drawings of the sun's surface
and of various other celestial phenomena. He devised the
bolometer for a detailed study of the intensity of the radiations
from different parts of the solar spectrum, and from other
bodies.
In 1887, Langley became Secretary of the Smithsonian
Institution, where he founded the Smithsonian Astrophysical
Observatory and carried on a long series of bolometric
determinations.
Langley was a pioneer in aerodynamics, and was almost the
first to make a heavier-than-air machine which could fly. He
was the author of many scientific papers, and his achievements
met with wide recognition. He received the degree D.C.L.
from Oxford, and D.Sc. from Cambridge, England; Ph.D.
from Stevens Institute of Technology, and LL.D. from several
American universities. He never married.
Truman Henry Sajford, 1836 to 1901; Staff Member, 1854 to
1865. Professor Safford was graduated from Harvard College
with special honors at the age of eighteen, and worked for a
time in the Cambridge office of the American Ephemeris and
Nautical Almanac. Newcomb, in his Reminiscences, refers to
him as "the most wonderful genius in the office, and the one who
would have made the most interesting subject of study to a
psychologist." Safford was, in his youth, and indeed through-
out his life, what is known as a " lightning calculator." He
himself was reticent as to this unusual endowment, but his
reputed ability in this line was marvellous. While at the
Harvard Observatory, he accomplished a large amount of valua-
258 LEADING MEMBERS OF THE OBSERVATORY STAFF
ble work, chiefly in the astronomy of position. He took a prom-
inent part in the observation and reduction of the zones of faint
stars observed near the equator with the 1 5-inch telescope,
and of meridian circle observations. The results are contained
in the Annals, 2, Part 2; 4; and 6. He also assisted Professor
G. P. Bond in the determination of the positions of stars in
the Great Orion Nebula and after Bond's death carried out the
publication of his observations, as given in Volume 5 of the
Annals. He was in charge of the Observatory for several
months after the death of Bond, until the appointment of
Winlock as director.
Safford was chosen Professor of Astronomy in the old
University of Chicago in 1865, an d Director of the Dearborn
Observatory. In 1876, he became Field Memorial Professor
of Astronomy at Williams College, where he remained until his
death in 1901.
Arthur Searle, 1837 to 1920; Staff Member, 1868 to 1920.
Professor Searle was born in London, October 21, 1837. His
mother was of English birth, but his father, though living
in England, was of New England ancestry, a descendant of
Thomas Dudley, second Governor of Massachusetts.
Searle was graduated from Harvard College in 1856, the
second scholar in his class. For twelve years he engaged in a
variety of pursuits, until in 1868 he was offered a position as
assistant at the Harvard Observatory. Although he accepted
the position in a tentative way, he soon became so interested in
his work that he remained in the Observatory until his death,
a period of over 52 years, by far the longest term of service of any
member of the staff. For 44 years he was in active service, and
for the last eight years, as Professor Emeritus, he still carried
on some astronomical work.
Searle received a formal appointment in 1869, was made
Assistant Professor in 1883, and Phillips Professor of Astronomy
in 1887. From the death of Winlock in 1875 until Pickering
assumed the directorship in 1877, Searle performed the duties
of acting director, and spent much of his time in preparing for
GEORGE MARY SEARLE 259
publication the observations already made. He also wrote
a history of the Observatory from the close of Professor Bond's
history, given in Volume I of the Annals, until the year 1876;
it is published in Volume 8 of the Annals.
Searle's chief work was the study of the zodiacal light
and, especially, the observation of the zone of stars from 9 50'
to 14 10', south declination. He also took a large part in the
early observations of the Harvard Photometry. He wrote
many articles for scientific and popular journals, as well as a
textbook on astronomy.
Searle was a man of unusually broad culture. Although
he made a successful career as an astronomer, he had no special
desire in his youth to become one. He would probably have
made an equal success as a mathematician, a linguist, a philoso-
pher, or a teacher. As a diversion he wrote verse both in Latin
and English, some of which appears to show real poetic spirit.
He also wrote on mathematical and philosophical subjects.
Professor Searle was singularly unassuming. With talents
which, with strong ambition, might have carried him to almost
any position in the scholarly or scientific world, he was content
to allow his life to flow on quietly; a strenuous life had no
appeal to him. Quiet and retiring, with an appearance almost
of gruffness, he yet showed himself, once his attention was
attracted, as one of the most genial and lovable of men.
George Mary Searle, 1839 to 1918; Staff Member, 1866 to
1868. George M. Searle, brother of Professor Arthur Searle,
was born in London, June 27, 1839, and died in Washington,
July 7, 1918. He was graduated from Harvard College in
1857, and was given the honorary degree of Ph.D. by the
Catholic University of Washington in 1896. He was an
assistant at the Dudley Observatory, 1858 to 1859; with the
Coast Survey, 1859 to 1862; Assistant Professor at the United
States Naval Academy, 1862 to 1864; and assistant at the
Harvard Observatory, 1866 to 1868.
He adopted the Roman Catholic faith in 1862, and left the
Harvard Observatory in 1868 to become a member of the
260 LEADING MEMBERS OF THE OBSERVATORY STAFF
Paulist Order. The remainder of his life was passed as a
member of that Order; he carried on some astronomical work
and was for a time Professor of Mathematics in the Catholic
University of Washington. For many years Father Searle
was Superior General of the Paulist Order in the United States.
He was the author of several books and pamphlets. In 1916 he
retired to the Apostolic Mission House, Washington.
Charles Sanders Peirce, 1839 to 1914; Staff Member, 1868 to
1875. Mr. Peirce, son of the celebrated mathematician
Benjamin Peirce, was born in Cambridge, Massachusetts,
September 10, 1839, and died in Milford, Pennsylvania, April
19, 1914. A man of brilliant attainments in several fields,
he applied his energies at different times to mathematics,
philosophy, logic, astronomy, and other branches of science.
During the latter part of his varied career, he lived in retirement
at Milford.
Peirce acted as assistant at the Observatory under Professor
Winlock, in 1868 and 1869, an d later during the years 1872
to 1875. I* 1 the latter period, he was really an assistant of
the United States Coast Survey, but was directed by the
Superintendent in 1871 to report to Winlock for duty as
assistant at the Harvard Observatory. An arrangement was
made by which a Zollner astrophotometer was obtained and
Peirce carried out during the next three years photometric
observations of 494 stars in declination +40 to +50. He also
carried out a discussion of the brightness of the stars as observed
by Ptolemy, Sufi, Argelander, Heis, and others. The results
are given in Volume 9 of the Annals.
Peirce was a member of the National Academy of Sciences
and a Fellow of the American Academy of Arts and Sciences.
He was the author of many memoirs and articles on a wide
variety of subjects. He was a contributor to the Century
Dictionary and to various encyclopaedias. Peirce had one
of the keenest minds which have appeared in American history,
but his later life was somewhat clouded by the eccentricities of
genius.
JOHN RAYNER EDMANDS 261
Oliver Clinton Wendell, 1845 to 1912; Staff Member, 1879 to
1912. Professor Wendell was born at Dover, New Hampshire,
on May 7, 1845. He was graduated from Bates College in
1868. From this college, also, he received the degree of M.A.
in 1871, and of D.Sc. in 1907. He was made Assistant Pro-
fessor of Astronomy at the Harvard Observatory in 1898.
Soon after graduation in 1868, Wendell became a student
at the Harvard Observatory under Winlock, but was compelled
to give up this work within a year on account of illness. For
about ten years he found it necessary to engage in out-of-door
pursuits, but he returned to the Harvard Observatory in 1879,
remaining there until his death in 1912.
His work at the Observatory was done in large part with
the i5-inch refractor. During the latter part of his life he was
almost the only observer with this telescope, and his relation
with it was in the nature of an intimate friendship. The early
glamour of the " Great Telescope" never lost its hold upon him.
His work was chiefly in photometric lines. He assisted in
carrying out a long series of observations of the eclipses of
Jupiter's satellites, and he was especially interested in comets
and in the computation of their orbits. His work is published
in the Annals, in volumes 13, 23, 24, 33, 37, 52, and 69.
He was married in 1870 to Sarah Butler, who died in 1910.
Two sons survived them.
John Rayner Edmands, 1850 to 1910; Staff Member, 1880 to
1910. Mr. Edmands became an assistant at the Observatory in
1880, although his name first appears in the official list of the
staff, as published in the University Catalogue, in 1883. His
work at the Observatory was chiefly in connection with the
time service into which he introduced several ingenious improve-
ments. He also served as Librarian of the Phillips Library
for many years. His position was that of a volunteer assistant,
more than that of a paid employee.
Edmands was a graduate of the Massachusetts Institute
of Technology, class of 1869. His chief interests in life, aside
from the work at the Observatory, were connected with the
262 LEADING MEMBERS OF THE OBSERVATORY STAFF
Appalachian Mountain Club, in which as councillor of topo-
graphy his training as a mechanical engineer rendered him
especially efficient. At different times he occupied all the
offices of the club, including that of President. He gave time,
energy, and money freely to the construction of mountain
paths, some of which in his honor have become known as the
"Edmands Trails."
Mr. Edmands was born in Boston in 1850, and died in
Baltimore in 1910.
Winslow Upton, 1853 to 1914; Staff M ember, 1877 to 1879.
Professor Upton was born in Salem, Massachusetts, October
12, 1853, and died in Providence, Rhode Island, on January
8, 1914. He received the degree of A.B. from Brown Uni-
versity in 1875, an d was given the honorary degree of Sc.D.
by the same institution in 1906. From 1875 t I ^77 ^ e was
student assistant at the Mitchel Observatory of the University
of Cincinnati, receiving there the degree of A.M.
Upton's life was full of incident. From 1877 to 1879 he was
assistant at the Harvard Observatory, under the direction of
Professor Pickering. In 1879 to 1880 he was assistant engineer
in the United States Lake Survey; in 1880 to 1881, computer
in the Naval Observatory; and from 1881 to 1883, computer and
Assistant Professor of Meteorology in the United States
Signal Service. He was appointed Professor of Astronomy at
Brown University in 1883, and remained in this position until
his death in 1914. Also, he was director of the Ladd Observa-
tory from its foundation in 1891. For many years he was Dean
of Brown University.
Upton took part in six expeditions to observe total eclipses
of the sun and passed the year 1896 to 1897 at Arequipa, where
he determined accurately the position of the southern station
of the Harvard Observatory.
While an assistant at the Harvard Observatory in Cambridge,
Upton took part in the photometric observations carried on
with the large refractor during 1877 to 1879, the results of which
are given in Volume II of the Annals. As Secretary of the
WILLIAMINA PATON FLEMING 263
New England Meteorological Society, he also supervised the
publication of the observations by the members of that Society,
contained in Volume 21 of the Annals.
Professor Upton was an accomplished musician and also a
humorist; while at the Harvard Observatory he wrote a skit
entitled "The Observatory Pinafore," which was much
admired for its bright and friendly satire. 1
Williamina Paton Fleming, 1857 t 1911 ', Staff Member, 1881
to 1911. Mrs. Fleming was born in Dundee, Scotland, May 15,
1857, and died in Boston, May 21, 1911. Her maiden name was
Paton. In early womanhood she married James 0. Fleming
with whom she came to the United States and settled in Boston.
Soon finding it desirable to support herself, she began work at
the Observatory in 1881. At first her duties were of the
simplest routine character. As her ability became apparent,
she was advanced to an important position. Perhaps her most
valuable service was in executive and administrative work. It
was a period of rapid development at the Observatory under the
direction of Professor Pickering, who was busy with many lines
of work, especially the introduction of photographic methods.
Mrs. Fleming exercised efficient supervision over a large staff
of computers and in addition rendered able assistance in the cor-
rection of copy and proof for the published results in the
Annals and elsewhere. As the collection of photographs of
the sky grew larger, she received the official title of Curator of
Astronomical Photographs.
A large part of Mrs. Fleming's scientific work was related
to stellar spectra. The director assigned to her the examina-
tion of the photographic plates, and also the classification of the
spectra of the stars contained in the Draper Catalogue. During
the execution of these duties, her active mind led her to many
discoveries. Chiefly by means of their characteristic spectra,
she discovered ten new stars and more than three hundred vari-
ables. She also made extended lists of gaseous nebulae and of
1 This operetta was performed 50 years later by the staff of the Observatory
at the meeting of the American Astronomical Society in December 1929.
264 LEADING MEMBERS OF THE OBSERVATORY STAFF
stars of peculiar spectra. Her principal work is found in the
Annals, volumes 18, 26, 27, and 47, and in various lesser
publications.
Mrs. Fleming was an Honorary Member of the Royal
Astronomical Society of London, and Honorary Fellow of
Wellesley College. She was an active member of the American
Astronomical Society, and a recipient of the gold medal of the
Sociedad Astronomica de Mexico. Her interests in life were
many. She was of an intense and active nature, never idle.
She was at the same time scientific and domestic, and had rare
skill in the making of small gifts with her own hands. As a
descendant of the "fighting Grahams," she was a stern enemy,
but a most loyal and faithful friend. She had a magnetic,
sympathetic personality, which brought her many devoted
friends.
Henrietta Swan Leavitt, 1868 to 1921; Staff Member, 1902 to
1921. Miss Leavitt was born in Lancaster, Massachusetts,
July 4, 1868, and died in Cambridge, December 12, 1921.
The daughter of a clergyman, she was of old New England
ancestry and inherited in a somewhat chastened form the
stern virtues of her forefathers. Her sense of duty was strong,
and her devotion to her family, friends, and religion was
intense. She was deeply absorbed in her astronomical work,
dedicating herself to it with an almost religious zeal.
The scientific results obtained by Miss Leavitt are given in
the Annals, 60, Nos. 2, 4, and 5; 71, Nos. 3 and 4; 85, Nos.
i, 7, and 8; and in various Circulars and other publications.
Her work was related, for the most part, to the determination
of the photographic magnitudes of the stars. Under the
direction of Professor Pickering, she carried on with much
skill and originality the determination of the magnitudes
of a large number of stars near the North Pole, constituting
a Standard Sequence of magnitudes. These standards were
later extended to the 48 equal areas into which Pickering
had divided the sky, and still later, to the Selected Areas of
Kapteyn.
HENRIETTA SWAN LEAVITT 265
In addition to these activities, Miss Leavitt discovered
by means of the photographs of the sky in the Harvard col-
lection, four new stars, 2400 variable stars, and several asteroids.
She first noted, in connection with her research on the variables
in the Magellanic Clouds, the important fact that the length
of period bears a definite relation to the absolute magnitude.
CHAPTER XIX
RESEARCH ASSOCIATES OF THE OBSERVATORY
A NUMBER of investigators, some of them eminent men
of science, have been temporarily associated with the Observa-
tory in scientific research. In recent times, the great collection
of astronomical photographs has proved to be an additional
attraction to many, containing as it does an almost inex-
haustible supply of fundamental data.
Sydney Coolidge, 1825 ?/<? 1863. Coolidge became associated
with the Observatory in 1853 and gave to its service a large
share of his time and energy for seven years. He took an
important part in the chronometer expeditions, at that time the
best method of determining the difference in longitude between
the Observatory and a European station. For this purpose he
crossed the Atlantic several times in the slow ships of the
period, having in his care a number of chronometers. He
was also active in the observation of the faint stars in the
zone near the equator, begun by George P. Bond, but carried
forward chiefly by T. H. Safford and himself. Coolidge
received the honorary degree of A. M. from Harvard University
in 1857. He became a major in the Union Army after leaving
the Observatory and was killed in an engagement near Chicka-
mauga, in 1863.
Coolidge's full name was Phillip Sydney Coolidge, but
evidently he preferred to have it known as Sydney Coolidge,
which, with one or two exceptions, is the name used in the
Annual Reports, in various publications, and in the Quin-
quennial Catalogue of Harvard University.
Seth Carlo Chandler, 1846 to 1913. The name of Seth C.
Chandler does not appear in the Harvard Catalogue as an
official member of the Observatory staff. He was, however,
266
SETH CARLO CHANDLER 267
connected with the Observatory for many years, chiefly as a
volunteer observer and investigator, and was frequently
mentioned in the Annual Reports of the Director, from 1880
until the time of his death. He was born in Boston, September
1 6, 1846, and died in Wellesley Hills, December 31, 1913.
Chandler did not pursue a college education, but was pos-
sessed of a keen mathematical mind, and developed a lifelong
interest in astronomy. After graduation from the Boston High
School in 1861, he became private assistant to Dr. B. A. Gould,
thus obtaining his start in astronomy. He became Aide in
the United States Coast Survey in 1864. Declining an offer
to accompany Dr. Gould to Argentine, he became the actuary
of a New York life insurance company, and later accepted a
similar position in Boston. He carried on a successful business
career throughout life as an actuary, devoting his spare time
to astronomy.
One of his earlier accomplishments at the Harvard Observa-
tory was the development of the almucantar and his observa-
tions with it. The results are contained in Volume 17 of the
Annals. His work on variable stars was of recognized value
in the early development of the subject, and his lists of such
stars were authoritative as long as they were maintained,
until the beginnings of photographic discoveries revolutionized
the subject.
Associated with Mr. John Ritchie, Chandler formulated
and introduced a convenient code for the telegraphic trans-
mission of astronomical discoveries. He computed the orbits
of many comets. He was a brilliant and rapid computer and
knew no limit to his time and energy when engaged on an
interesting problem. Probably his most remarkable work
was the series of masterly papers proving the reality of the
variation of latitude.
Mr. Chandler was Editor of the Astronomical Journal
from 1896 to 1909; a member of the American Academy of
Arts and Sciences, the National Academy of Sciences, and
many others. He received the Watson Gold Medal of the
268 RESEARCH ASSOCIATES OF THE OBSERVATORY
National Academy, and the gold medal of the Royal Astronomi-
cal Society. In 1891, he received from De Pauw University
the honorary degree of LL.D. Professor Searle said of his work:
"His powers of intellect were creative rather than critical;
in other words, he has left among those who knew him
the remembrance not so much of mere talent as of positive
genius."
Abbott Lawrence Rotck, 1861 to 1912. The name of Abbott
Lawrence Rotch appears for many years on the staff of the
Harvard Astronomical Observatory, as given in the annual
catalogue of the University. Rotch, however, was not a
salaried employee of the Observatory, but, for greater efficiency
in his chosen line of meteorology, he associated himself with
the institution by special arrangement with the director, Edward
C. Pickering. Rotch was a Bostonian of large wealth and scien-
tific tastes, who, becoming absorbed in meteorological studies,
founded in 1885 the Blue Hill Meteorological Observatory
as a private institution, maintained and directed by himself.
The Annals of the Harvard Observatory contain the chief
results of the Blue Hill Observations from 1887 to 1924.
It was expected by Professor Pickering and Professor Rotch
that both institutions would ultimately be united under one
control. At his death in 1912 Rotch bequeathed his observa-
tory to the Corporation of Harvard University, who accepted
the gift, but made the Blue Hill Meteorological Observatory a
separate department of the University.
For many years Rotch held the appointment of Assistant in
Meteorology, but in 1906 he was made Professor of Meteorol-
ogy in recognition of his service to that science. His position in
both cases was honorary, and carried with it no salary. Under
his direction, the Blue Hill Observatory achieved a world-wide
reputation, for Rotch was a pioneer in the study with kites
and sounding balloons of the meteorological conditions in the
upper air.
Jod Hastings Metcalf, 1866 to 1925. Dr. Metcalf was born
at Meadville, Pennsylvania, January 4, 1866, and died February
JOEL HASTINGS METCALF 269
4, 1925, at Portland, Maine. In three lines of endeavor he
achieved considerable success. First of all he was a preacher, a
minister in its best sense, of the Unitarian Church. One of
the charming traits of his character was a wide tolerance
closely associated with an intense religious faith. He held
the degrees of D.D. and Ph.D. and was successful both as
pastor and lecturer.
The second absorbing interest in Metcalf 's life was astronomy.
His passion for this science began in boyhood and lasted
throughout his life. As a small boy he made his first telescope
with a lens which he worked hard to purchase. During his
first pastorate at Burlington, Vermont, he established his
first observatory. In 1903, he went to Oxford University for a
year's study of theology, but devoted all his spare time to
astronomical problems, through the courtesy of Professor
Turner. In the following year he accepted a pastorate at
Taunton, Massachusetts, and built and equipped a new private
observatory. There he first became associated with the
Harvard Observatory and a firm friend and admirer of Professor
Pickering.
Metcalf not only made astronomical observations of value,
but these observations were obtained with telescopes of his
own construction. It was in applied optics that his highest
scientific work was done. As an expert in this line he probably
had no superior. He not only computed his own curves for
the lenses, but possessed a genius for bringing them to perfec-
tion. Altogether, he ground many lenses. Perhaps the most
notable of these was the 1 6-inch doublet, a photographic
instrument which has been in use at the Harvard Observatory
for many years. At the time of his death he was at work on a
i3-inch triplet, the largest lens of this type ever attempted;
the lens was later completed by Lundin for the Lowell Observa-
tory and has become famous through its use in the discovery
of the planet Pluto.
For his discoveries of comets, Metcalf received five medals.
He also discovered a number of new variable stars, and 41
270 RESEARCH ASSOCIATES OF THE OBSERVATORY
new minor planets. He was a member of the American
Astronomical Society and a Fellow of the American Academy
of Arts and Sciences. For many years he was Chairman of the
Visiting Committee of Harvard Observatory, as well as a
member of the Visiting Committee of the Ladd Observatory.
It must be remembered that all these activities were in addition
to the arduous duties of the pastor of a large church.
The third interest in Metcalf s life was associated with the
World War. He became a secretary of the Young Men's
Christian Association, and sought service at the front. By
choice he shared the perils and discomforts of the private.
His conduct endeared him to his associates, and he was cited
for bravery at Chateau-Thierry.
Henry Gannett, 1829 to 1915. Geographer, United States
Geological Survey, 1882 to 1915. Dr. Gannett was assistant
at the Observatory, 1870 to 1872.
Nathaniel S. Shaler, 1841 to 1906. Professor of Geology,
Harvard University. Beginning in 1871, Professor Shaler
made an elaborate study of the surface of the moon from the
viewpoint of a geologist, using the large refractor.
Henry M. Parkhurst, 1825 to 1908. Parkhurst was a stenog-
rapher for the United States Senate from 1848 to 1856, and
for the Superior Court, New York City, from 1871 to 1891.
He was an able and enthusiastic amateur astronomer, carrying
on researches on asteroids and variable stars for many years
at his private observatory. His results are published in the
Harvard Annals, 18, No. 3, and 29, Nos. 3 and 4, and appendix.
He also made many contributions to scientific journals.
Dana P. Bartlett, 1863 to .Professor Bartlett (Professor
of Mathematics in the Massachusetts Institute of Technology)
was an assistant at the Observatory in 1887, and took part
in the expedition to Colorado (pp. 55-56).
Harry E. Cli/ord, 1866 to .Professor Clifford (Gordon
McKay Professor of Electrical Engineering, Harvard Uni-
versity) was an assistant at the Observatory in 1887, and also
took part in the expedition to Colorado.
JACOBUS C. KAPTEYN 271
George Ellery Hale, 1868 to . Dr. Hale, Honorary
Director of the Mount Wilson Observatory, was a volunteer
research assistant at the Observatory in 1889 to 1890.
Robert DeCourcy Ward, 1867 to . Professor Ward, now
Professor of Climatology in Harvard University, passed several
months at the Arequipa branch of the Observatory in 1897.
While there, he carried on meteorological research, and made
an inspection of the various meteorological stations at that
time maintained by the Observatory in southern Peru.
George K. Burgess, 1874 to . Dr. Burgess, Director
of the Bureau of Standards, Washington, was a student assistant
at the Observatory in 1897.
Frederick W. Grover, 1876 to . Professor Grover (Asso-
ciate Professor of Electrical Engineering, Union College,
Schenectady; Consulting Physicist, Bureau of Standards,
Washington) was a volunteer observer at the Observatory in
1899.
Ralph A. Sampson, 1866 to . Professor Sampson
(formerly Professor of Mathematics in Durham University;
Astronomer Royal for Scotland) discussed, at Professor
Pickering's request, the photometric observations of Jupiter's
satellites made at the Harvard Observatory from 1878 to 1903.
The results of the discussion are given in Harvard Annals,
52, Part 2, published in 1909.
Clarence A. Chant, 1865 to . Professor Chant, now
Professor of Astronomy in the University of Toronto, carried
out volunteer research work on variable stars in 1916. His
study of the light curve of W Virginis is given in Harvard
Annals, 80, No. 12.
Herbert C. Wilson, 1858 to .Professor Wilson (Pro-
fessor of Astronomy and Director Emeritus of the Goodsell
Observatory, Carleton College) pursued research on variable
stars at Harvard in 1916. His investigation of the light curve
of T Andromedae is published in Harvard Annab, 80, No. 8.
Jacobus C. Kapteyn, 1851 to 1922. During the directorship
of Edward C. Pickering, cooperation was effected between the
272 RESEARCH ASSOCIATES OF THE OBSERVATORY
Harvard and Groningen Observatories in the execution of
Kapteyn's systematic Plan of Selected Areas. The Harvard
Observatory undertook to furnish durchmusterung plates
of all the Selected Areas, visual and photographic magnitudes
of the desired stars, and the classification of spectra. The
reductions were all made under Professor Kapteyn's direction.
The results of this cooperation are given in the Harvard Annals,
101, 102, and 103. After Kapteyn's death in 1922, this
cooperation was continued by his successor, Dr. van Rhijn.
Ejnar Hertzsprung, Professor of Astronomy, University of
Leiden, Holland. Professor Hertzsprung spent seven months
in 1926 to 1927 at the Observatory in the study of short period
variable stars on the Harvard photographs. He made 11,000
estimates of magnitude and obtained results bearing on the
discovery, previously made by him, of a systematic relation
of the form of the light curve to the length of period among
typical Cepheid variables.
Some account has been given in Chapter VII of the coopera-
tion of Professors Henry N. Russell, of Princeton, and Ernest
W. Brown of Yale, in the photographic determination of the
moon's position.
In recent years a number of volunteer research assistants
have carried on various investigations at the Observatory.
Among them may be mentioned Martha B. Shapley (Mrs.
Harlow Shapley); Miss Margaret Harwood, Director of the
Maria Mitchell Observatory at Nantucket; Dr. Priscilla
Fairfield, Professor of Astronomy at Smith College; Dr.
Theodore Dunham, of Mount Wilson Observatory; Dr. Donald
H. Menzel, of Lick Observatory; Professor Issei Yamamoto, of
Kyoto; Dr. Charles Lassovszky, of Budapest; Dr. Paul Davido-
vich, of Moscow; Professor S. D. Townley, of Stanford Uni-
versity; and Professor B. P. Gerasimovi, of the University
of Kharkov, Russia.
CHAPTER XX
LIST OF OBSERVATORY STAFF MEMBERS
A LIST is given below of the members of the staff of the
Observatory since its beginning. During the directorship
of the Bonds and Winlock, the number of assistants did not
exceed three or four at any time, and was often less. At first,
the position of Assistant, formally appointed, was regarded
as an important one and is so used in this list. The rank of
First Assistant, in use at one time, was one of some distinction,
fully equal to the present rank of Assistant Professor of Astron-
omy. Later the number of assistants has often been as high
as 40, or even higher. Many of these, however, were students
or others whose services, irregular and brief, consisted in the
routine duties of the different departments of the Observatory.
In general these have not been included in the list, but only
those who were regularly employed in astronomical work for a
year or more. The term of service occasionally includes a
brief interval of absence. The list contains the names of
both living and deceased members, to the end of 1927. It is
divided into two sections; with a few exceptions, the first
contains those members whose appointments were made
by the Corporation, arranged in chronological order, and the
second, those appointed by the directors, arranged in alpha-
betical order.
273
274 LIST OF OBSERVATORY STAFF MEMBERS
MEMBERS OF THE OBSERVATORY
Name
Position
Term of
Service
Wiliam C. Bond
Director; Phillips Professor, 1849 to
1839-1859
1859
George P. Bond
Director; Phillips Professor, 1859 to
1846-1865
1865
Charles W. Tuttle
Assistant
1850-1854
P. Sydney Coolidge
Research Associate
1853-1860
Truman H. Safford
Assistant
1854-1865
Joseph Winlock
Director, Phillips Professor
1866-1875
Arthur Searle
Phillips Professor, 1887 to 1912
1868-1920
Charles S. Peirce
Assistant
1868-1875
William A. Rogers
Assistant Professor
1870-1886
Leonard Waldo
Assistant
1875-1880
Edward C. Pickering
Director; Phillips Professor, 1877 to
1877-1919
1887; Paine Professor, 1887 to 1919
Winslow Upton
Assistant
1877-1879
Oliver C. Wendell
Assistant Professor
1879-1912
John R. Edmands
Assistant
1880-1910
Seth C. Chandler
Research Associate
1880-1913
Mrs. Williamina P. Fleming
Curator of Astronomical Photographs
1881-1911
Abbott L. Rotch
Professor; Director, Blue Hill Meteor-
1886-1912
ological Observatory
Willard P. Gerrish
Assistant Professor
1886-
*William H. Pickering
Assistant Professor
1887-
*fSolon I. Bailey
Phillips Professor, 1912 to 1925
1887-
Edward S. King
Phillips Professor, 1926 to
1887-
Miss Antonia C. Maury
Research Associate
1888-
Miss Annie J. Cannon
Curator of Astronomical Photographs
1896-
*Leon Campbell
Astronomer
1899-
Miss Henrietta S. Leavitt
Assistant
1902-1921
Harlow Shapley
Director, Paine Professor
1921-
Willard J. Fisher
Research Associate
1922-
Willem J. Luyten
Assistant Professor
1923-
*fjohn S. Paraskevopoulos
Assistant Professor
1923-
Miss Cecilia H. Payne
Astronomer
1923-
Boris P. Gerasiniovic"
Research Associate
1926-
LIST OF OBSERVATORY STAFF MEMBERS
MEMBERS OF THE OBSERVATORY. (continued)
275
Name
Term of
Service
Name
Term of
Service
Miss Adelaide Ames
1923-
Henry Gannett
1870-1872
Miss Mary Applegate
1918-1920
R. W. Gifford
1886-1888
(Mrs. Beach)
Miss Edith F. Gill
1889-
William H. At will
1888-1902
Miss Mabel A. Gill
1892-
Edward P. Austin
1869-1871
Frederick W. Grover
1899
*Hinman C. Bailey
1893-1002
Asaph Hall
1857-1862
* Marshall H. Bailey
1888-1891
Miss S. H. Hall
1897-1900
Darsie C. Bard
1899-1900
(Mrs. Bonesteele)
Dana P. Bartlett
1887
Miss Mildred L. Hannon
1927-
Philip S. Bates
1011-1914
Miss Maude E. Harriman
1900-1905
Robert Black
1888-1890
Miss Margaret Harwood
1907-1912
*Herbert E. Blackett
19081911
Miss Marian A. Hawes
1912-1918
*L. C. Blanchard
1916-1918
Guy Hill
1904-1905
*tMiss Dorothy W. Block
1917-
*Philip P. Hill
1905-1911
(Mrs. Paraskevopoulos)
*Frank E. Hinkley
1907-1918
Miss Selina C. Bond
18791920
Miss Lillian L. Hodgdon
1889-
Frank L. Bowie
1904-
Frank S. Hogg
1920-
Miss Constance D. Boyd
1926-
Miss Helen E. Howarth
1923-
David E. Brand
1911-1912
Miss Mary B. Howe
1924-1925
Frederick E. Brasch
1902-1904
Miss Mary E. Howe
1907-1909
Miss Sarah E. Breslin
1898-1912
A. Jansen
1892-1894
Miss Grace R. Brooks
1906-1920
J. Arthur Jennison
1889-1891
Wilbur V. Brown
1879-1883
Everett T. King
1911-1916
George K. Burgess
1897
Harold S. King
19161921
Miss Irma W. Caldwell
1926-
Samuel P. Langley
1865-1866
Miss Florence M. Campbell
1925-
Anson S. Leard
1905-1908
Leon Campbell, Jr.
1921-1927
Miss Evelyn F. Leland
1889-1925
Miss Alta M. Carpenter
1906-1920
Miss Helen M. Lewis
1927-
Samuel C. Catterall
1908-1911
(Mrs. Thomas)
Miss Geraldine E. Clark
1926-1927
Augustus McConnel
1870-1871
Harry E. Clifford
1887
Joseph F. McCormack
1872-1880
*William B. Clymer
1895-1900
Charles E. McCullar
1900-1905
Harold R. Colson
1895-1905
Miss Amy J. McKay
1891-1906
Harold St. C. Cook
1916-1918
Miss Johanna C. S. Mackie
1903-1920
Ernest R. Cram
1894-1902
*Edmund S. Manson
1902-1907
Leland E. Cunningham
1925-
Miss Frances Cooper- Marshal
1926-1927
Miss Florence Cushman
1888-
Miss Annie E. Masters
1887-1889
Arthur W. Cutler
1880-1884
Miss Genevieve F. Mathews
1912-1916
Miss Mary Daniel
1927-
*H. Mechelhof
1893-1894
Robert S. Davidson
1893-1898
Miss Marion F. Michaelis
1900-1906
*Andrew E. Douglass
1890-1894
Miss Jenka Mohr
1927-
*Luis Duncker
1890-1894
*Juan C. Muniz
1922-1925
John A. Dunne
1888-1909
*Juan E. Muniz
1895-1925
Miss Madalen R. Dwyer
1926
Miss Muriel E. Mussells
1927-
Clifford C. Eaton
1881-1884
Miss Sylvia F. Mussells
1927-
Mrs. I. W. Eddy
1889-1904
T. Oliver Olsen
1914-191?
Miss Margaret B. Evans
1927-
Miss Mollie E. O'Reilly
1906-1918
Miss Nettie A. Parrar
1881-1885
(Mrs. Sloan)
Frederick E. Fowle
1888-1890
Philip G. O'Reilly
1910-1914
Miss Carol G. Fox
1927-
*Harold I. Peckham
1912-1915
John H. Freese
1901-1902
Thomas E. Powe
1890-1893
*Royal H. Frost
1896-1908
Miss Susan Raymond
1916-1917
276 LIST OF OBSERVATORY STAFF MEMBERS
MEMBERS OF THE OBSERVATORY. (continued)
Name
Term of
Service
Name
Term of
Service
William M. Reed
1890-1900
*George T. Vickers
1890-1893
John Ritchie
1883-1892
*Elias Vieyra
1880-1900
Mrs. R. T. Rogers
1875-1898
*C. J. G. Vogel
1910-1911
Miss Helen J. Roper
1926-
Edward B. Waite
1894-1900
Willard I. Rowe
1907-1910
Frank Waldo
1878-1881
Miss Jennie T. Rugg
1887-1889
Miss Arville D. Walker
1906-
John D. Runkle
1853
Miss Emma E. Walker
1912-1918
Miss R. G. Saunders
1875-1888
Miss Margaret L. Walton
1924-
Miss Helen B, Sawyer
1926
(Mrs. Mayall)
Henry A. Sawyer
1920-
*George A. Waterbury
1893-1898
Arthur R. Sayer
1927-
Miss Ruth C. Waterbury
1907-1910
fL. G. Schultz
1909-1910
William F. H. Waterfield
1920-
George M. Searle
1866-1868
Miss Louisa D. Wells
1887-
Miss Katharine Searle
19041912
William W. White
1900-1909
Howard R. Shaw
1906-1908
Miss Marion C. Whyte
1911-1913
*I. Franklin Snow
1906-1907
Robert W. Willson
1874-1875
Miss Beatrice L. Sparks
1923-1924
Miss Harvia H. Wilson
1924-1925
Miss Harriet I. Stevens
1891-1910
Miss Jane B. Wilson
1912-1913
Miss Ida M. Stevens
1904-1909
Hobart W. Winkley
1887-
Miss Mabel C. Stevens
1888-1906
Miss Anna Winlock
1875-1903
*Delisle Stewart
1896-1902
Miss Louisa Winlock
1886-1915
Miss Nellie C. Storm
1887-1889
William C. Winlock
1876-1880
Rufus O. Suter
1923-1926
Miss E. Gertrude Wolffe
1893-1899
Miss Henrietta H. Swope
1926-
Miss Doris Wood
1927-
Miss Helen Symonds
1925-1926
(Mrs. Wills)
E. Leopold Trouvelot
1872-1874
Miss Ida E. Woods
1893-
Horace P. Tuttle
1858-1862
*Benjamin F. Wyeth
1902-1905
*In Peru.
t In South America.
CHAPTER XXI
BENEFACTORS OF THE OBSERVATORY
THE foundation and development of the Harvard Observa-
tory has been due in large part to private gifts. Although the
beginnings of the Observatory at the Dana House were chiefly
the result of University enterprise and especially of the enthu-
siastic interest of President Quincy, the establishment of the
new Observatory on a firm foundation was accomplished through
the generosity of the public-spirited business men of Boston,
and patrons of science elsewhere.
Past and Present Benefactors. A consideration of the
benefactors of the Observatory should include some mention
of men not generally regarded as such. The Bonds, especially
W. C. Bond, by the arduous service which they gave for the
first six years without salary, alone made possible the establish-
ment and maintenance of the Observatory at that time. W. C.
Bond gave not only his time but much of the early equipment.
Edward C. Pickering, during his long directorate, frequently
made contributions toward the running expenses of the Observa-
tory. Here, also, should be mentioned the name of the Rever-
end Joel H. Metcalf, who gave the time and skill necessary to
grind several photographic lenses, which have been of much
value to the Observatory.
The contributions of the University to the Observatory
have been large. At the beginning, the Corporation undertook
to provide the necessary grounds and buildings for the Dana
House Observatory, and to devote to its use whatever apparatus
was in the possession of the College. The University, however,
had no funds with which to give it an endowment or provide for
its expenses. Nevertheless, as shown by the Report of the
277
278 BENEFACTORS OF THE OBSERVATORY
Treasurer of Harvard College in 1846, the University advanced
considerable sums toward the completion of the new Observa-
tory and its equipment. 1 Recently the University contributed
about $200,000 toward the transfer of the Boyden Station
to South Africa and toward its equipment, and the International
Education Board (Rockefeller) gave an equal amount.
The American Academy of Arts and Sciences has often shown
an interest in the Observatory, and in the early and difficult
years, in 1839 and again in 1843, contributed several thousand
dollars for the purchase of apparatus. A thousand dollars was
also given at that time by the Boston Society for the Diffusion of
Useful Knowledge. The greater part of the funds, however,
which have made possible the growth of the Observatory, have
come from private individuals. The gifts began with the
building and equipment of the new Observatory, when Mr.
David Sears offered $5000 for a tower to contain the large
refractor, on the condition that $20,000 should be contributed
by others for the purchase of the telescope. This sum was
promptly raised by subscriptions made chiefly in Boston. Mr.
Sears later gave an additional $5000.
The first large gift toward the permanent endowment of
the Observatory came in 1848 on the death of Edward Bromfield
Phillips, a college classmate of George P. Bond, who bequeathed
to the Observatory $100,000, a large sum for those days.
The income from this fund first permitted the payment of
salaries, and also provided something toward other necessary
expenses.
Citizens of Boston contributed $5000 toward the running
expenses of the Observatory in 1846, a time of serious financial
difficulties. Again in 1851, several thousand dollars were
contributed, by many donors, to meet urgent needs. In 1855
the Observatory received the fund of $10,000 from President
Quincy, given in honor of Josiah Quincy, Jr. This fund has
been of special aid in publication. Nathaniel Bowditch had
been influential in the establishment of the Observatory, and
1 H. A., i, xc, 1846.
PAST AND PRESENT BENEFACTORS 279
his son, J. Ingersoll Bowditch, was for many years a firm and
generous friend.
At the beginning of the administration of Edward C. Picker-
ing, the income of the Observatory was still scant and inade-
quate, and appeals for aid were frequent. Many thousand
dollars were thus raised to meet the increasing expenses. A
much larger activity was made possible in 1886 with the Paine
Fund, which in all amounted to about $400,000; and in 1887
by the Boyden Fund of about $230,000. The contributions
of Mrs. Henry Draper during her life, and her bequest in 1914
for the work of the Henry Draper Memorial, amounted to
several hundred thousand dollars.
In 1898, two bequests without restrictions were received, one
of $20,000 by the will of Charlotte Maria Haven, and one of
$25,000 by the will of Eliza Appleton Haven. In 1902, an
anonymous gift of $20,000 was received from a donor who
preferred not to have his name announced.
The number of small contributors to the Observatory has
been numerous as many as 300 since the beginning of its
history. Brief sketches of the lives of the more prominent
deceased benefactors are given below.
The Observatory is fortunate, also, in its friends now living.
The following deserve special gratitude, since their gifts have
been carefully and wisely directed in aid of worthy current
investigations, for the prompt publication of results which
otherwise would have been delayed, and for the foundation
of astronomical fellowships:
Mr. George R. Agassiz, of Boston
Mrs. James R. Jewett, of Cambridge
Mrs. Charles S. Hinchman, of Philadelphia
Mr. Gerard Swope, of New York
Mr. C. W. Elmer, of New York
Mrs. C. W. Elmer, of New York
Edward Bromfield Phillips, 1826 (about) to 1848. The first
considerable sum given for the maintenance of the Observatory
was the bequest of Edward B. Phillips, who died in 1848.
280 BENEFACTORS OF THE OBSERVATORY
Mr. Phillips entered Harvard College in 1841, and was
graduated in 1845. He was a classmate of George P. Bond,
which probably accounts in part at least for his keen interest
in astronomy. It was found after his unfortunate death in
1848 that he had bequeathed $100,000 to the Observatory.
It is difficult now to appreciate how much this meant to those
who were at that time struggling to maintain the reputation
of the Observatory with an utterly inadequate income. This
really munificent gift saved the institution from possible
failure, and started it afresh on an upward career.
In honor of the donor, the Corporation early established
the Phillips Professorship of Astronomy, and gave to the library
connected with the Observatory the name " Phillips Library."
Robert Treat Paine, 1803 to 1885. Robert Treat Paine was
born in Boston, October 12, 1803, and died in Brookline,
June 3, 1885. He was a grandson of Robert Treat Paine, one
of the signers of the Declaration of Independence. Mr. Paine
had from boyhood until old age an intense interest in astron-
omy. He always remembered the comet of 1811, which he
maintained was not equalled by any comet which he observed
later.
By profession Mr. Paine was a lawyer, but the great passion
of his life was for astronomy and meteorology. For nearly
60 years he himself made a continuous series of meteorological
observations in his home in Boston and later in Brookline.
Mr. Paine's astronomical observations were made with
portable instruments. He had exceptional skill with the
sextant, and was appointed chief engineer of the survey of the
State of Massachusetts. His special astronomical interest
was in the motion of the moon as determined by occult at ions
and eclipses. During his life he computed over 2000 occulta-
tions and observed many of them. During 60 years no solar
eclipse occurred near Boston which was not observed by him if
the weather permitted. In all he observed in different places
nine total or annular eclipses of the sun. To observe the total
eclipse of 1880, although more than seventy six years of age,
PAST AND PRESENT BENEFACTORS 281
he travelled alone to California. At the age of eighty two he
was planning to observe the eclipse of March 16, 1885, in
Montana, and was prevented only by sickness and approaching
death. He showed his devotion to astronomy by bequeathing
his entire fortune, amounting to more than a quarter of a
million dollars, to the Harvard Observatory. In his honor
the Paine Professorship of Practical Astronomy was established,
and since then that professorship has been conferred on the
Director of the Observatory. Formerly the director held the
title of Phillips Professor of Astronomy, a place which has later
been held by the chief assistant.
Uriah Atherton Boyden, 1804 to 1879. Mr. Boyden, for
many years a mechanical engineer of Boston, was born in
Foxborough, Massachusetts, in 1804, an d died in Boston in
1879. His devotion to science was shown in various ways
during his life and by his bequest to astronomy at his death.
Mr. Boyden, in 1859, deposited with the Franklin Institute
of Philadelphia the sum of $1000, to be awarded as a prize to
any resident of North America who should determine by
experiment whether or not all rays of light and other physical
rays are transmitted with the same velocity. The Franklin
Institute advertised the offer for many years, and 25 or 30
papers were presented, none of which was deemed worthy
of the prize. At length in 1907, nearly half a century after
the offer was first made and many years after Boyden's death,
the prize was awarded to Dr. Paul R. Heyl, then of Philadelphia.
Dr. Heyl found by elaborate experiments on Algol that, in a
distance of 40 light years, the difference of the velocities of
the ultra-violet and visual rays could not exceed one part in
two hundred and fifty thousand.
In 1862, Mr. Boyden published in the Journal of the Franklin
Institute, Volume XLIV, a paper entitled "On Explosions
produced by Nitre in Burning Buildings, etc."
Mr. Boyden left by will a sum amounting to about $230,000
for the establishment of a mountain observatory at such an
altitude as to avoid, so far as possible, the ill effects of the
282 BENEFACTORS OF THE OBSERVATORY
earth's atmosphere. The fund was placed in the hands of a
Board of Trustees, who, in 1887, transferred it to the President
and Fellows of Harvard College for the use of the Observatory.
The southern station of the Observatory, formerly at Arequipa,
Peru, and now at Mazelspoort, South Africa, is known as the
"Boyden Station."
Miss Catherine Wolfe Bruce. About 1888, Miss Bruce,
of New York City, became interested in Professor Pickering's
plan for the construction of a powerful photographic doublet.
As a result of this interest she gave, in 1889, $50,000 for the
construction and care of such an instrument. Several years
were needed in which to secure the glass discs and to do the
grinding. The resulting telescope, a photographic doublet
of 24 inches aperture, was called the "Bruce Telescope/' It
is described in Chapter IV.
Experimental work was begun with this instrument late in
1893. In 1895 it was removed to Arequipa, Peru, where for
more than 30 years it gave important results. Remounted
and transferred to the new Boyden Station in South Africa, it
still has many years of great usefulness.
Miss Bruce showed her interest in astronomy by numerous
smaller gifts to the Observatory and to astronomers elsewhere.
In 1890 she gave $6000 to be distributed during the year in
aid of astronomical science anywhere. Through the aid of
Professor Pickering, sums of $500 or less were contributed to
various investigators in different countries. She found much
pleasure in the contacts thus made with prominent astronomers.
Miss Bruce gave assistance also to Barnard at the Yerkes
Observatory and Wolf at Heidelberg, in the purchase of photog-
raphic telescopes; to Weinek at Prague in the publication of
his Moon-Atlas; and to the Lick Observatory for the purchase
of photometers. In 1897 she presented a fund of $2500 to
the Astronomical Society of the Pacific, to make possible the
yearly award of a gold medal "for distinguished service to
Astronomy." The first award was made in 1897, to Simon
Newcomb.
PAST AND PRESENT BENEFACTORS 283
Miss Bruce, whose health had always been delicate, died in
New York City in 1900.
Mrs. Henry Draper. Anna Palmer Draper, daughter of
Courtlandt Palmer and wife of Dr. Henry Draper, died in New
York City, December 8, 1914.
Mrs. Draper, from the time of her marriage until the sudden
death of Dr. Draper in 1882, was an enthusiastic and unselfish
companion and aid in all his investigations. Dr. Draper was
a pioneer in astrophysics, and had a private laboratory and an
observatory. It is said that he never went to his observatory
without Mrs. Draper, his sympathetic and intelligent assistant.
Mrs. Draper, after the death of her husband, planned at
first to establish an observatory in New York City, as a memo-
rial to him. She finally decided, however, to found a depart-
ment at the Harvard Observatory, for the study of the spectra
of the stars. This research became known as the " Henry
Draper Memo rial. " For the prosecution of this work, Mrs.
Draper gave large sums during many years, and at her death
bequeathed a substantial amount to increase the permanent
endowment of the Observatory. Mrs. Draper was by no means
satisfied with the gift of money, but always exhibited a keen
and intelligent interest in the progress of the investigations.
The results of the Draper Memorial have been not only
voluminous but of immense value in the progress of astronomy.
The largest publications concerned in it are: The Draper
Catalogue, Annals, 27, giving a classification of the spectra
of 10,351 stars; and the Henry Draper Catalogue of more
than 200,000 stars, covering the whole sky, occupying Volumes
91 to 99 of the Annals.
Charles Robert Cross, 1848 to 1921. Professor Cross was
born at Troy, New York, on March 29, 1848. His great-
grandfather, Robert Cross, was a major in the American Army
of the Revolution.
Mr. Cross entered the sophomore class of the Massachusetts
Institute of Technology in 1867, and obtained his training
under President Rogers and Professor Edward C. Pickering.
284 BENEFACTORS OF THE OBSERVATORY
On his graduation in 1870, he became Instructor in Physics
at that institution, and was made Professor of Physics in
1875. From then until his retirement in 1917 he was an
influential factor in the development of the Institute.
Mr. Cross served as scientific expert for the Bell Telephone
Company. Early recognizing the importance of electrical
development, he gave the first course in Electrical Engineering
in this country, and wrote many papers on electrical subjects.
He was a member of various scientific societies, and for many
years was Chairman of the Rumford Committee of the American
Academy of Arts and Sciences.
Mr. Cross had a keen love of astronomy and generally
attended the annual meetings of the American Astronomical
Society, although seldom or never taking part in the proceed-
ings. For many years he was a member of the Visiting
Committee of the Harvard Observatory. His deep interest in
the Observatory may be traced, at least in part, to his profound
regard for Edward C. Pickering, its Director, whose pupil in
physics he had been at the Institute. This may account for the
bequest of the greater part of his fortune to the Harvard
Observatory. The bequest will finally amount to more than
a hundred thousand dollars.
NAME INDEX
Adams, John C., n
Adams, John Quincy, n, 13, 14, 20, 21
Adams, Walter S., 167
Agassiz, George R., 279
Aldrich, L. B., 66
Ames, Adelaide, 98, 209, 213, 275
Andre*, 174
Applegate, Mary, 275
Appleton, 24
Arago, 115
Argelander, 124, 129, 170, 173, 174,
175, 260
Atkinson, 9
Atwill, W. II., 275
Austin, Edward P., 196, 275
B
Bache, 51
Bailey, H. C, 61, 275
Bailey, Irving, 58, 59
Bailey, M. H., 58, 59, 60, 275
Bailey, Mrs. Solon I., 56, 58, 59, 60,
192
Bailey, Solon L, 36, 45, 56, 57, 58, 59,
60, 61, 64, 66, 93, 132, 133, 142,
167, 181, 182, 183, 192, 193, 197,
200, 201, 203, 274
Baily, 5
Bard, Darsie C., 275
Barnard, 120, 282
Bartlett, Dana P., 270, 275
Bates, Philip S., 275
Bauer, L. A., 104
Bauschinger, 99
Bernard (Governor), 6
Bessel, 26
Bird, 15
Black, 33, 135, 233
Black, Robert, 56, 57, 192, 275
Blackett, Herbert E., 275
Blanchard, L. C., 61, 275
Block, Dorothy W. (Mrs. Paraske-
vopoulos), 69, 275
Bond, Elizabeth Lidstone, 224
Bond, Elizabeth Lidstone, 226, 228
Bond, George P., 18, 22, 28, 32, 33,
38, 39, 4i, So, 51, 70, 73, 79, 81,
85, 86, 94, 105, 108, 116, 117, 122,
135, 148, 194, 195, 196, 197, 217,
2l8, 222, 224, 226-236, 237, 240,
253, 256, 258, 259, 266, 273, 274,
277, 278, 280
Bond, Hannah Cranch, 218
Bond, Hannah Cranch (Mrs. William
C. Bond), 218
Bond, Joseph Cranch, 224
Bond, Richard F., 39, 51, 224
Bond, Selina Cranch, in, 224, 275
Bond, Selina Cranch (Mrs. William
C. Bond), 224
Bond, William, 217
Bond, William C., Jr., 18, 103, 224
Bond, William Cranch, 12, 13, 14,
15, 17, 18, 20, 28, 29, 30, 32, 33,
35, 38 39, 40, 4i, 70, 7i, 73, 79,
86, 100, 103, 104, 105, 108, 109,
no, 116, 148, 194, 195, 217-226,
227, 228, 229, 230, 231, 232, 233,
237, 240, 253, 273, 274, 277
Bowditch, J. Ingersoll, 19, 23, 28,
225, 227, 235, 279
Bowditch, Nathaniel, j.o, 12, 278
Bowie, Frank L., 275
Boyd, Constance D., 275
Boyden, Uriah A., 55, 281-282
285
286
NAME INDEX
Brand, David E., 275
Brasch, Frederick E., 275
Brashear and McDowell, 48
Brattle, Thomas, 5
Brattle, William, 5
Breslin, Sarah E., 181, 275
Brooks, Grace R., 275
Brown, Ernest W., 85, 272
Brown, W. V., in, 275
Bruce, Catherine W., 43, 282-283
Briinnow, 255
Bunsen, 148
Burgess, George K., 271, 275
Butler, Sarah (Mrs. Oliver Wendell),
261
Byrd, Mary E., 106
Caldwell, Irma W. (Mrs. Wallace),
275
Campbell, Florence, 275
Campbell, Leon, 61, 67, 75, 80, 177,
178, 186, 191, 274
Campbell, Leon, Jr., 275
Campbell, W. W., 129
Cannon, Annie J., 36, 45, 67, 142, 154,
155, 156, 157, 158, 159, 160, 161,
162, 163, 164, 165, 172, 177, 180,
186, 248, 274
Carpenter, Alta M., 275
Catterall, Samuel C., 275
Chandler, Seth C., 95, 172, 173, 266-
268, 274
Chant, Clarence A., 271
Cilley, W. H., 56
Clark, Alvan, and Sons, 40, 41, 42, 43,
44, 45, 46, 119, 128, 135, 245
Clark, Alvan G., 57
Clark, Geraldine E., 275
Clay, Henry, 237
Clifford, Harry E., 270, 275
Clymer, William B., 106, 275
Colson, Harold R., 275
Common, 47, 48
Cook, Harold St. C., 275
Cooke, T., and Sons, 48
Coolidge, Sydney, 51, 86, 108, 196, 266,
274
Cram, E. R., 63, 275
Cranch, 26
Crawford, Russell T., 56
Cross, Robert, 283-284
Cunningham, Leland E., 275
Cushman, Florence, 134, 275
Cutler, Arthur W., 275
D
Daguerre, 115
Dana, Richard H., 17
Daniel, Mary, 275
Davidovich, Paul, 166, 188, 272
Davidson, Robert S., 275
Davis, 9
Davis (Judge), 12
Davis, Lt. C. H., 106, 238
Dawson, 9
Delambre, 12
Douglass, A. E., 45, 60, 61, 63, 90, 275
Draper, Anna Palmer (Mrs. Henry
Draper), 44, 149, 158, 279, 283
Draper, Henry, 44, 118, 119, 149, 152,
158, 283
Draper, John W., 116, 118
Dudley, Thomas, 258
Duncker, Luis, 275
Dunham, Theodore, Jr., 169, 272
Dunne, J. A., 275
Dwyer, Madalen R., 275
Eastwood, 32
Eaton, C. C., 275
Eddy, Mrs. I. W., 112, 275
Edmands, John Rayner, 261-262, 274
Eliot, Charles, 245
Eliot, S. A., 24
Elmer, C. W., 279
Elmer, Mrs. C. W., 279
Encke, 229, 232
Enebo, 188
Evans, Margaret B., 275
Everett, Edward, 218, 223
NAME INDEX
287
Fabricius, 170
Fairfield, Priscilla (Mrs. Bok), 272
Farrar, 12, 13, 225
Farrar, Nettie A., 275
Fechner, 124
Fecker, J. W., 48, 69
Felton, 17
Ferguson, 219
Ferrel, 238
Fisher, W. J., 68, 74, 85, 97, 98, 90, 274
Flams teed, 5
Fleming, James O., 263
Fleming, Williamina Paton (Mrs.
James O. Fleming), 98, 136, 151,
154, 164, 165, 181, 186, 193, 196,
263-264, 274
Foster, Thomas, 17
Fowle, Frederick E., 275
Fox, Carol G., 275
Franklin, 6, 10
Fraunhofer, 25, 40, 148, 149
Freese, John H., 275
Frost, R. H., 61, 197, 275
Galileo, 3
Gannet, Henry, 53, 270, 275
Gauss, 15, 103
Gerasimovic", B. P., 272, 274
Gerrish, Willard, 45, 49, 121, 274
Gifford, R. W., 275
Gill, Sir David, 64
Gill, Edith F., 275
Gill, Mabel A., 181, 275
Gore, 12
Gould, 32, 237, 239, 240, 267
Graham, James D., 26, 105, 225
Greely, 56
Grover, Frederick W., 271, 275
Grubb, Sir Howard, 45
Hall, 9
Hall, Asaph, 87, 108, 228-229, 254-
255, 275
Hall, S. H. (Mrs. Bonesteele), 275
Halley, 7
Hannon, Mildred L., 275
Harriman, Maude E., 275
Harvard, John, 4
Harwood, Margaret, 68, 94, 109, 112,
272, 275
Haven, Charlotte Maria, 279
Haven, Elizabeth Appleton, 279
Hawes, Marion A., 275
Heis, 124, 260
Henry Brothers, 43, 120, 136
Herbst, 41
Herschel, Sir John, 124, 125, 126, 22^
Herschel, Sir William, 124, 125, 175,
196, 223
Hertzsprung, 129, 167, 208, 272
Hilgard, 242
Hilger, 130
Hill, 32
Hill, Guy, 275
Hill, Philip P., 275
Hinchman, Mrs. Charles S., 279
Hinkley, Frank E., 61, 275
Hipparchus, 123
Hodgdon, Lillian, 112, 275
Hogg, Frank, 169, 275
Holden, 226, 231, 234
Hollis, 6
Holwarda, 170
Houzeau, 124
Howarth, Helen, 98, 275
Howe, Mary B., 275
Howe, Mary E., 275
Hubble, 212
Huggins, 1 1 8, 149
Humboldt, 102, 103
Hadley, 7
Hale, George Ellery, 271
Jansen, A., 275
Jennison, J. Arthur, 275
Jewett, Mrs. James R., 279
288
NAME INDEX
Kapteyn, J. C., 142, i43 U4> 271-272
Kelvin, n
Kerr, 32
King, 9
King, Edward S., 44, 56, 57, 67, 68,
80,^82, 85, 88, 89, 99, 121, 122,
137, 138, 139, 141, 145, J 46, 181,
192, 206, 274
King, Everett T., 275
King, Harold S., 275
Kirchhoff, 148
Kirkland, 12, 14
Klotz, Otto, 107
Kohlschtitter, 165, 167
Kiistner, 114
Langley, Samuel P., 53, 86, 256-257,
275
Laplace, 10
Lassell, 232
Lassovszky, Charles, 272
Lathrop, 12
Lawrence, Abbot, 24
Leard, Anson, S., 275
Leavitt, Henrietta S., 137, 140, i4 r
142, 143, 145, 161, 172, 1 80, 182,
184, 185, 202, 208, 210, 264-265,
274
Legendre, 10
Leland, Evelyn F., 180, 181, 275
Leverrier, n
Lewis, Helen M. (Mrs. Thomas), 275
Lind, Jenny, 96
Lindblad, 167, 213
Loud, F. H., 56
Levering, 15, 18, 20, 103
Lowell, John, 12
Lundin, 269
Lundmark, 213
Luyten, Willem J., 68, 206, 274
Lyle, James, 65
M
McAteer, C. Y., 189, 191
McConnel, Augustus, in, 275
MacCord, V. H., 56
McCormack, J. F., in, 275
McCullar, Charles E., 275
McKay, Amy J., 275
Mackie, Johanna C. S., 188
Madler, 199
Manson, Edmund S., 275
Marshal, Frances Cooper-, 275
Masters, Annie E., 275
Mathews, Gene vie ve F., 275
Maury, Antonia C. de P. P., 152-154,
155, 156, 157, 167, 274
Mechelhof, H., 275
Meirung, Izak, 65
Menzel, D. H., 272
Merz and Mahler, 25, 40, 239
Metcalf, Joel, H., 44, 48, 93, 268-270,
277
Michaelis, Marion, 112, 275
Mitchel, n, 39
Mitchell, Maria, 238
Mitchell, S. A., 178
Mitchell, William, 96, 118, 233
Mohr, Jenka, 275
Morris, William, 64, 65
Miiller, 92
Muftiz, Juan C., 275
Muniz, Juan E., 61, 275
Mussells, Muriel E., 275
Mussells, Sylvia F., 275
N
Newcomb, Simon, 32, 238, 242, 257,
282
Newton, 3, 5
O
Olcott, William Tyler, 189
Oliver, 32
Olsen, T. Oliver, 275
Oppolzer, 93
NAME INDEX
289
O'Reilly, Mollie E. (Mrs. Sloan), 275
O'Reilly, Philip G., 275
Paine, Robert Treat, 280
Paine, Robert Treat, 19, 227, 280-281
Palmer, 17
Palmer, Courtlandt, 283
Paraskevopoulos, Dorothy, 69, 275
Paraskevopoulos, John S., 61, 66, 67,
69, 274
Parkhurst, Henry M., 92, 174* 270
Payne, Cecilia H., 68, 74, 75, 169, 274
Peabody, 17, 19
Peckham, Harold I., 275
Peirce, Benjamin, u, 15, 18, 24, 31,
32, 33, 52, S3, 86, 103, 224-226,
230, 238, 241
Peirce, Charles S., 52, S3, 86, 95, no,
124, 125, 196, 198-199, 240, 260,
274
Perouse, 218
Perrine, 90
Peters, 32
Phillips, 12
Phillips, Edward Bromfield, 30, 3*,
278, 270-280
Pickering, David B., 189
Pickering, Edward C., 35, 36, 42,
43, 45, 46, 47, 52, 53, 55, 5&, 6o >
64, 70, 7i, 72, 73, 80, 81, 85, 86,
87, 88, 92, 97, 109, in, 119, 120,
121, 126, 127, 128, 131, 132, 133,
134, 135, 139, 140, 141, 142, 148,
149, 151, 152, 154, 155, 157, 158,
159, 160, 164, 165, 166, 167, 170,
171, 173, 174, 175, 176, 177, 179,
180, 183, 185, 189, 193, 196, 199,
200, 207, 217, 243-252, 258, 262,
263, 264, 268, 269, 271, 274, 277,
279, 282, 283, 284
Pickering, John, 24
Pickering, Lizzie Sparks (Mrs. Edward
C. Pickering), 251
Pickering, William H., 42, 44, 45, 49,
54, 55, 56, 57, 60, 61, 63, 66, 80,
82, 83, 84, 89, 90, 91, 95, 98, 119,
120, 121, 135, 195, 201, 274
Pogson, 124, 126, 127, 170
Powe, Thomas E., 275
Pritchard, 130
Ptolemy, 123, 125, 126, 260
Quincy, Josiah, 4, 5, 6, u, 14, 15, iQ,
20, 24, 221, 224, 225, 227, 277,
278
Quincy, Josiah, Jr., 278
Raymond, Susan, 275
Reed, W. M., 172, 177, 276
Rensselaer, 9
van Rhijn, P. J., 144, 272
Ritchie, John, 267, 276
Rittenhouse, 6
Rogers, Mrs. R. T., 276
Rogers, William A., 34, 41, no, in,
112, 241, 255-256, 274
Rogers, William B., 244, 283
Romana, L. de, 60
Roper, Helen J., 276
Rosen, 124
Rosse, 223, 232
Rossiter, R. A., 69
Rotch, A. Lawrence, 56, 61, 101, 268,
274
Rowe, Willard I., 276
Rugg, Jennie T., 276
Rumker, 50
Runkle, John, D., 32, 238, 276
Russell, Henry Norris, 85, 86, 175, 272
Ryder, Maud, 210
Safford, Truman H., 32, 33, 35, 108,
no, 195, 196, 231, 238, 257-258,
266, 274
290
NAME INDEX
Sampson, Ralph Allen, 88, 271
Saunders, R. G., in, 276
Sawyer, Helen B. (Mrs. Frank Hogg),
183, 193, 194, 210, 276
Sawyer, Henry A., 276
Sayer, Arthur R., 276
Schmidt, 175, 176
Schdnfeld, 124, 131, 170, i?4, i?S, i?6
Schultz, L. S., 65, 200, 276
Seagrave, F. E., 177
Scares, 144, 239
Searle, Arthur, 35, 41, 42, 52, 81, 87,
88, 92, 101, in, 112, 127, 128,
130, 196, 241, 258-259, 274
Searle, George M., 86, 95, no, 196,
259-260, 276
Searle, Katharine, 112, 276
Sears, David, 19, 24, 278
Secchi, 149, 151, 156
Seidel, 124, 125
Sewall, 9
Shaler, Nathaniel S., 34, 82, 240, 270
Shapley, Harlow, 22, 37, 48, 66, 67,
68, 70, 72, 74, 75, 98, 143, 158,
159, 160, 161, 162, 163, 167, 168,
169, 175, 182, 183, 185, 193, 194,
197, 2OI, 2O2, 2O3, 2O4, 2O5, 2O6,
207, 208, 209, 210, 211, 212, 213,
217, 240, 249, 274
Shapley, Martha B. (Mrs. Harlow
Shapley), 168, 272
Shaw, Howard R., 276
Shirakawa, 55
Simms, 26, 27, 222
Snow, I. Franklin, 276
Sparks, Beatrice L., 276
Sparks, Jared, 70, 251
Stevens, Harriet L, 276
Stevens, Ida M., 276
Stevens, Mabel C., 181, 276
Stewart, Delisle, 93, 276
Stickney, Miss (Mrs. Asaph Hall), 255
Stokes, Sir George S., 45
Storin, Nellie C., 276
Struve, 42, 84, 117, 124, 230
Stifl, 123, 124, 125, 260
Sumner, Thomas H., 10-11
Suter, Rufus O., 276
Swope, Gerard, 279
Swope, Henrietta H., 205, 276
Symonds, Helen, 276
Taylor, H. Dennis, 48
Thompson, Benjamin (Count Rum-
ford), 10
Todd, David, 55
Townley, S. D., 272
Troughton and Simms, 13, 15, 17, 26,
41, 241
Trouvelot, E. Leopold, 34, 79, 83, 192,
240, 254, 276
Turner, H. H., 269
Tuttle, Charles W., 51, 86, 108, 196,
253, 274
Tuttle, Horace Parnell, 253-254, 276
Tycho Brahe, 124, 125
U
Ulugh Beg, 124, 125
Upton, Winslow, 56, 62, 63, 92, 106,
in, 127, 196, 262-263, 274
Vernon, 9
Vickers, George, 60, 61, 276
Vieyra, Elias, 59, 276
Vogel, 1 66
Vogel, C. J. G., 276
Voigtlander, 42
W
Waite, Edward B., 177
Waldo, F., 87, 276
Waldo, Leonard, 274
Walker, 39
Walker, Arville D., 142, 143, 276
Walker, Emma E., 276
Walton, Margaret L. (Mrs. Mayall),
211, 276
NAME INDEX
2QI
Ward, Robert DeCourcy, 271
Washington, 6
Waterbury, George A., 276
Waterbury, Ruth C., 197, 276
Waterfield, William F. H., 276
Webber, 12
Weinek, 282
Wells, Louisa D., 181, 276
Wendell, Oliver, 47, 87, 88, 89, 92,
93, 95, 96, 128, 131, 134, 174, 175,
177, 178, 196, 261, 274
Whipple, 33, 82, 116, 135, 233
White, William W., 276
Whitney, Mary W., 106
Whyte, Marion C., 276
Wilkes, 39, 221
Willard, Joseph, 8
Williams, Samuel, 8, 9
Willson, Robert W., 276
Wilson, H. C., 189, 271
Wilson, Harvia H., 211, 276
Wilson, Jane B., 276
Wilson, R. E., 208
Winkley, Hobart W., 276
Winlock, Anna, in, 276
Winlock, Fielding, 237
Winlock, Joseph, 237
Winlock, Joseph, 32, 33-34, 35, 4i,
52, 53, 70, 86, 92, 95, 108, no,
125, 148, 196, 198, 217, 237-243,
249, 254, 256, 258, 260, 261, 274
Winlock, Louisa, 112, 276
Winlock, William C., 276
Winthrop, 9
Winthrop, John, 6-7
Winthrop, Robert C., 104
Witt, 93
Wolf, 136, 282
Wolff, 124
Wolff e, Gertrude E., 276
Wood, Doris (Mrs. Wills), 276
Woods, Ida E., 182, 183, 188, 276
Wright, 32
Wyeth, Benjamin F., 276
Yamamoto, Issei, 211, 272
Young, Charles A., 53, 55
Zollner, 124
SUBJECT INDEX
Absorption of light in space, 138-139,
206
Accademia dei Lincei, 224
Alfred University, 256
Algol, 281
Allegheny Observatory, 165, 257
Almagest, 123, 124
Almucantar, 113-114, 267
American Academy of Arts and Sci-
ences, 9, 15, 18, 20, 23, 82, 103,
194, 224, 235, 252, 256, 260, 267,
270, 278
founding, 8
Rumford Committee of, 54, 284
American Association for the Advance-
ment of Science, 238, 256
American Association of Variable
Star Observers, 22, 178, 179, 189-
191, 249
American Astronomical Society, 31,
32, 252, 263, 264, 270, 284
American Ephemeris and Nautical
Almanac, 31, 238, 239, 257
American Philosophical Society, 7, 224
Andromeda, Great Nebula in, 27, 194,
212, 213, 225
T Andromedae, 271
Annals of Harvard College Observa-
tory, 18, 28, 29, 33, 35, 42, 53, 54,
70-71, 72, 79, 81, 83, 88, 91, 97,
in, 133, 138, 146, 153, 156, 157,
172, i75> 192, 231, 250, 253, 254,
258, 259, 260, 261, 262, 263, 264,
268, 270, 271, 272, 283
Appalachian Mountain Club, 245, 262
Arago medal, 255
Arequipa (see Harvard College Obser-
vatory, Boyden Station).
Argelander's Uranometria, 125
Arica, 106
Asteroids, 12, 92-94
announcement, 73
discovery, 265, 270
photometry, 87, 175
positions, 34, 42
Astrographic Congress, 43
Astrographic Map of Sky, 142, 146
Astrometry, 108-114
Astronomer Royal of Scotland, 88, 271
Astronomical Journal, 50, 240, 267
Astronomical Society of the Pacific,
282
Astronomische Gesellschaft Zones, 34,
41, 42, 110-113, 249
Astronomische Nachrichten, 238
Atacama, Desert of, 59
Aurora, spectroscopy, 240
B
Baily's beads, 54
Bards town (eclipse station), 52
Bates College, 261
Bell Telephone Company, 284
Binaries, eclipsing (see Eclipsing bin-
aries).
spectroscopic (see Spectroscopic bin-
aries).
Binary stars, 34
(See also Double stars.)
Bloemfontein, 65, 66, 68-69
Bloemfontein Station of 1/utroit Obser-
vatory of University of Michigan,
69
Blue Hill, 17, 97
293
2Q4
SUBJECT INDEX
Blue Hill Meteorological Observatory,
71, 101, 268
Bond Astronomical Club, 22
Bond Zones, 108-110, 130, 134, 196,
232, 253, 266
Bond's Ring of Saturn, 27, 86, 222,
225, 230
Bonn Durchmusterung, 124, 125, 129,
131, 136, 146
Boston Marine Society, 24
Boston Society for the Diffusion of
Useful Knowledge, 278
Boyden Expeditions, 55-56
Boyden Fund, 36, 55, 58, 102, 279
Brown University, 256, 262
Bureau of Standards, United States,
271
California, University of, 56
Callao, 59
Cambridge Astronomical Society, 31
Cape Photographic Durchmusterung,
146
Carleton College, 271
Carnegie Institution, 58, 104
Catholic University of Washington,
259, 260
o> Centauri, 181, 183, 192193
Central College, 254
Cepheid variables, 37, 171, 179, 183,
202, 203, 205
5 Cephei, 171
in Small Magellanic Cloud, 184, 208
observations, 175, 272
W Virginis, 271
(See also Cluster variables.)
Chachani, 61, 89
Chicago, University of, 258
Chosica station, 59, 132
Chronograph, 38-39, 223-224
Chuquicamata station, 66-67
Cincinnati Observatory, n, 262
Class, distribution of stars of each
spectral, 159-163
A, 138, 139, 140, HI, i5S
Class, B, 155
F, 140, 155
G, 155
K, 141, 155, 160
M, 138, 155, 206
Md, 156, 179
O, 155, 207
P, iSS
Q, 155
Cloverdon Observatory, 239
Cluster variables, 45, 61, 180, 203
Clusters, 36, 48, 192-193
drawings, 192
galactic (see Open clusters).
globular (see Globular clusters).
monograph, 74
open (see Open clusters).
photographs, 57
Colby College, in, 256
Colorado College, 56
Colorado Eclipse Expedition, 55-56,
270
Comet-seeker, 28
Comets, 1811, 219, 280
1843, 23, 94, 225
announcement of, 73
discovery, 254, 269
Donati's (1858), 33, 94, 195, 229, 231
Halley's, 12
observations, 26, 33, 36, 94-95, 219,
221, 232
orbits, 232, 253, 254, 267
positions, 34
Swift's (1892), 95
Cordoba Durchmusterung, 124, 146
Craigie estate, 25
Cross Bequest, 284
Crystal Palace Exposition, 39
6 1 Cygni, 12
X Cygni, 190
P Cygni type variables, 210
Cygnus cloud, spectra in, 159
Dearborn Observatory, 258
Deimos, 87
SUBJECT INDEX
295
De Pauw University, 268
30 Doradus (N. G. C. 2070), 210
Dorpat Observatory, 25
Double stars, 45, 48
ft Aurigae, 167
observations, 175, 240
photographs, 57
V Puppis, 167
/x 1 Scorpii, 167
spectroscopy, 164, 166-167
f Ursae Majoris, 166-167
(See also Eclipsing binaries.)
Doublets, photographic, 42-44
Draper, Henry, Catalogue of Stellar
Spectra, 36, 42, 71, 145, 146, 150-
163, 248, 263, 283
Draper, Henry, Memorial, 44, 119,
120, 149, 152, 159, 164, 165, 179,
279, 283
Draper classification, 154-156, 283
Dudley Observatory, 259
Durchmusterung, of clusters and
nebulae, 193
of variable stars, 180
Durham, University of, 88, 271
E
Eclipse (see Moon, eclipse; Solar
eclipse).
Eclipsing binaries, 37, 167, 171, 175,
176, 205
Edinburgh, University, 7
El Misti, 62, 102
Eros, 93-94, 249
Extra-galactic nebulae, 212
Extra-galactic systems, 211-213
F
Falmouth, 52
Field Memorial Professor (Williams
College), 258
Fireballs, Sept. 30, 1850, 96
study of, 99
Foreign Associates of the Royal
Astronomical Society, 222, 224,
236
Franklin Institute, 281
French Academy of Sciences, 255
Galactic system, 37, 198206
Gaseous nebulae, 48, 263
in Small Magellanic Cloud, 211
Gegenschein, 81, 92
Geodesy, 104-107
Globular clusters, 37, 48, 180, 192-
iQ3, 203, 204, 205
to Centauri, 181, 183, 192-193
classification, 193
durchmusterung, 193
Hercules Cluster, 210
in Magellanic Clouds, 210
Messier 3, 181-182, 183
Messier 5, 181, 183
Messier 15, 183
N. G. C. 3201, 183
N. G. C. 6205, 192
N. G. C. 6341, 192
N. G. C. 6362, 183
N. G. C. 6752, 182
variable stars in, 181
Goodsell Observatory, 271
Gordon McKay Professor (Harvard),
270
Gottingen Observatory, 141
Greenwich Observatory, 3, 13, 225
Grenada (eclipse station), 54
Groningen Observatory, 144, 272
H
Hamburg Observatory, 50
Hanover (O. F. S.), 65, 200
Harvard College, founding, 4
Report of the Treasurer (1846), 278
Harvard College Observatory, Annals
(see Annals of Harvard College
Observatory).
Announcement Cards, 73
Annual Report of Director, 48, 64,
7o, 72, 74, ioo, 189, 222, 246, 266,
267
296
SUBJECT INDEX
Harvard College Observatory, Annual
Report of the Visiting Commit-
tee, 70, 74
assistant, 20
benefactors, 277-284
Boyden Station, at Arequipa, Peru,
36, 42, 43, 48, 55, 57, 58, 59,
60, 61, 62, 63, 65, 66, 67, 68,
81, 89, 90, 93, 102, 106-107,
119, 132, 133, 135, 154, 157,
158, 167, 181, 184, 192, 197,
201, 207, 247, 262, 271, 282
at Mazelspoort, South Africa, 36,
43, 48, 55, 68, 69, 197, 278,
282
Bulletins, 72-73
chronometer expeditions, 51, 106,
266
Circulars, 71-72, 186
Curator of Astronomical Photo-
graphs, 263, 274
Dana House Observatory, 13, 14-15,
17-22, 23, 25, 41, 71, 100, 103,
115, 221, 277
endowment increased, 36
founding, 3, 11-16
instruments, 38-49
6o-inch Common reflector, 47-48,
49, 135
24-inch Bruce doublet, 42, 43, 49,
69, 120, 143, 197, 212, 247
24-inch reflector, 49, 139, 178
1 6-inch Metcalf doublet, 42,
43-44, 49, i43 269
15-inch equatorical refractor, 13,
21, 24, 25, 26-27, 33, 34, 35,
39-41, 47, 49, 82, 83, 86, 87,
92, 96, 108, no, 116, 117,
119, 126, 134, 175, 178, 194,
196, 223, 224, 225, 229, 233,
240, 246, 258, 261, 262, 270, 278
i5-inch reflector, 153
i3-inch Boyden refractor, 44-45,
49, 56, 57, 60, 119, 150, 152,
154, 181
12-inch (i35-foot) refractor, 48-
49, 63-64, 84
Harvard College Observatory, instru-
ments, i2-inch polar equato-
rial, 45
with meridian photometer, 45,
46, 134
n-inch Draper refractor, 44, 49,
89, 97, 119, 137, 150, 152, 153
lo-inch Metcalf triplet, 48, 49,
65, i45, 159
8J^-inch meridian circle, 34, 35,
41, 49, 108, HO-II2, 240-241,
243, 246, 256
8-inch Bache doublet, 42, 43, 49,
56, 59, 119, 135, 149, 150, 196
8-inch Draper doublet, 42, 49,
145, 146
4^:4 -inch transit circle 27, 41, 49,
no, 222
4-inch meridian photometer, 46,
49, 59, 60, 131-133, 134, 175
4-inch comet-seeker, 28, 49
Rogers transit (about 3-inch
aperture), 106
2-inch meridian photometer, 46,
49, 133
1.6-inch meridian photometer,
128-129
ij^-inch Cooke refractor, 98,
193, 200
See also Observatory Instruments,
49
longitude, 104-105
map of sky, 180
monographs, 74~75> J 94
naming, 19
observer, 20
Photometry, 71, 123-147
photographic, 47, 7*, I35-H4
revised visual, 133
southern, 59, 60, 61, 132
visual, 45, 46, 47, 58, 59, 60, 61,
124-147, 174-175, 200, 250, 259
(See also Photometry.)
present site, 25-26
reprints, 73~74
Standard Regions, 44, 134, 141-142,
144, 146, 161, 248, 264
SUBJECT INDEX
297
Harvard College Observatory, Stan-
dard Sequence, 264
Visiting Committee, 19, 21, 104,
270, 284
Harvard Hall, 7, 8
Heidelberg Observatory, 282
Hercules Cluster, 210
Hollis Professor (Harvard), 8, 10, 12,
18
Hyperion, 86, 232
Institute of France, 224
International Astronomical Union,
Committee on Spectral Classifica-
tion, 156, 158, 179
International Committee on Magni-
tudes, 139, 142
International Education Board, 68,
278
Island universes, 213
Islay, Desert of (Expedition), 67
Jamaican expedition, 1899, 63
1900-1901, 63-64, 80, 82
Jamaican station, 44
Jerez de la Frontera, 53, 241
Jupiter, eclipses of satellites, 88-89,
261, 271
observations of satellites, 175
outer satellites, 90
photographic observations, 89
photometry, 87
K
Kapteyn Selected Areas, 44, 134, 142,
143-144, 146, 248, 264, 272
Kapteyn System, 204, 206
Kharkov, University of, 272
Kiel, 72
Kyoto, Imperial University of, 272
Ladd Observatory, 262, 270
Lalande Prize, 255
Latitude variation, 267
Lawrence Scientific School, 243
Laws Observatory, 239, 240
Leander McCormick Observatory, 1 78
Legion of Honor, 255
Leiden, University of, 272
Leonid meteors, 12, 97-98
(See also Meteors.)
Lick Observatory, 165, 272
Lilla Eden, 50
Lima, 59
Linn6, 83, 84
Long period variables, 171, 175, 176,
177, 178, 179, 205
T Andromedac, 271
X Cygni, 190
Longitude determinations, 51, 104-
107, 262
Lowell Observatory, 80, 269
M
Magellanic Clouds, 48, 172, 180, 184,
185, 202, 205, 206-211, 212, 213
Large, 207, 209, 210, 211
parallax, 209-210
Small, 202, 208, 209, 210, 211
Magnetic observations, 18, 221
Magnetism, terrestrial, 102-104
Magnitude, photographic, "absolute
measures," 137-138
Magnitude scale, 123, 124, 126, 132
Mandeville, 63, 66
Maria Mitchell Observatory, 68, 94,
272
Mars, observations, 33, 91,
photometry, 87, 88
satellites, 87, 228, 246, 255
surface features, 90, 91
Massachusetts Bay Colony, 3, 4
Massachusetts Institute of Technology,
52, 54, 244, 261, 270, 283, 284
Mazelspoort, South Africa (see Harvard
College Observatory, Boyden Sta-
tion).
Mercury, transit, 8
Meridian circle (see Harvard College
Observatory, instruments).
298
SUBJECT INDEX
Messier 3, 181-182, 183
Messier 5, 181, 183
Messier, 15, 183
Meteorological observations, 18, 34,
55, 56, 61, 62, 63, 100-104, 221,
271
Meteorological Society of Harvard
University, 103
Meteors, 96-100
Leonids, 12, 97-98
Orionid radiant, 99
procession, 98
search for photographs, 98, 99
Michigan, University of, 255
Micrometer measures, no
Milky Way, 197, 198-206
Mina Avis (eclipse station), 61
Missouri, University of, 37, 239, 240
Misti Observatory, 62
Mitchel Observatory, 262
Mollendo, 62, 102, 106
Moon, brightness, 80, 81-82
determination of position, 44, 85-86
eclipses, 8, 84-85
Linn6, 83, 84
maps, 49, 83-84
motion, 280
observations, 61, 66
occupations, 89
photographs, 57, 83-84, 116
Plato, 83
possible satellite, 84
surface, 34, 82-84, 270
Mount Harvard, 59, 60, 132
Mount Pleasant, 52
Mount Washington, 5 1
Mount Wilson Observatory, 37, 58,
141, 144, 165, 167, 168, 182, 203,
212, 271, 272
6o-inch reflector, 140
Mount Wilson Station, 55-58, 192
N
National Academy of Sciences, 99,
236, 252, 256, 260; 267
National Observatory at Washington,
ii
Nebulae, 36, 42, 48, 194-19?
Andromeda, 27, 194, 212, 213, 225
diffuse, 48, 263
in Small Magellanic Cloud, 211
durchmusterung, 193
extra-galactic, 211-213
Messier, 33, 207
new, 196-197
Orion, 27, 33, 194, 195, 201, 210,
223, 225, 229, 230, 231-232, 258
photographs, 57
planetary, 205
positions, 195-196
spiral, 207
Neptune, n, 87
New England Meteorological Society,
71, 102, 263
New England Weather Service, 71
Newfoundland, expedition to, 6
Newton, 3
Newtown, 4
N. G. C. 2070 (30 Doradus), 210
N. G. C. 3201, 183
N. G. C. 6205, 192
N. G. C. 6341, 192
N. G. C. 6362, 183
N. G. C. 6752, 182
Nicola jew Catalogue, no
Nicolajew zone, 109
North Polar Sequence, 139-141, 142,
143, 144, 145, 146
Northern Durchmusterung, no, 200
Norwell, Mass., observations at, 201
Nova, 36, 42, 185-188, 205, 263, 265
announcement of, 73
Aquilae, No. 3, 165-166, 186-188
in Carina, 186
discovery from spectrum, 164, 248
Geminorum No. 2, 186, 187, 188
Persei, No. 2, 165, 186, 187
Pictoris, 1 66, 188
search for, 188
spectroscopy, 165-166
O
Obscuration of light, 199, 201
Observatory "Pinafore," 263
SUBJECT INDEX
299
Observer, Harvard Observatory, 3,
16, 20, 21, 221
Occultations, 221
Ocllo, 93
Open nights at Harvard Observatory,
22
Ordre pour la M6rite, 252
Orion lines, 155
Orion Nebula, 27, 33, 194, 195, 201,
210, 223, 225, 229, 230, 231-232,
. 2 . 58
Orionid radiant, 99
Oroya Railway, 56, 59
Overseers of Harvard University, 14
Oxford University, 269
Paine Fund, 279, 281
Paine Professorship of Practical
Astronomy (Harvard), 281
Pampa Central, 59, 66, 132
Parallaxes, spectroscopic, 167-168
Paris Observatory, 3
Period-luminosity law, 185, 202, 208,
211, 265
Perkins Professor (Harvard), 18, 20,
21, 31, 238
Peruvian Expeditions, 58-63
Peruvian Meteorology, 71
Phillips Bequest, 30, 31, 33, 278, 280
Phillips Library, 261, 280
Phillips Professorship (Harvard), 32,
240, 258, 280, 281
Phobos, 87
Phoebe, 90
Photography, celestial, 33, 36, 42,
52, 115-122, 225, 229, 232-235,
247
Photometer, kinds, 87
meridian (see Harvard College Ob-
servatory, instruments),
polarizing, 47, 88, 125-127
wedge, 130
Photometry, 123-147
asteroids, 87, 92, 94
Jupiter's satellites, 87, 271
Photometry, moon, 137
planets, 86-87, 137
sun, 79
variable stars, 134, 174-175
(See also Harvard College Observa-
tory, Photometry.)
Pikes Peak, 102
Planets, 86-92
conjunction, 87
intra-mercurial, search for, 63
observations, 36, 61, 66
photographs, 57
search for, 34
study of details, 45
(See also Asteroids.)
Plato, 83
Pleiades, 136, 201
Pluto, 269
Popular Astronomy, 179, 189, 191
Potsdam visual photometry, 144
Poulkova Observatory, 25, 41, 124, 243
Princeton University, 37, 85, 272
Proceedings of the American Academy,
171, 172
Proper motions, 206
f Puppis, spectrum, 155
Royal Academy of Arts and Sciences
(Paris), 6
Royal Astronomical Society, 3, 31,
231, 252, 255, 264, 268
Royal Bavarian Academy of Sciences,
235
Royal Microscopic Society, 256
Royal Society (London), 6, 15, 18,
103, 104, 256
Rshev (eclipse expedition), 55
San Jose" (southern station), 66-67
Santa Ana (meteorological station),
62, 102
Saturn, Bond's Ring, 27, 86, 222, 225,
230
3 oo
SUBJECT INDEX
Saturn, observations, 33, 86, 253
satellites :
Hyperion, 86, 222, 226, 230, 232
Phoebe, 90
Scorpio and Ophiuchus, star cloud in,
205-206
Sears Tower, 27, 29, 278
longitude, 105
Secchi's classification of spectra, 151,
156
Sheffield Scientific School of Yale
University, 256
Shelby College, 34, 237, 239, 240
Shelby ville (eclipse expedition), 52
Sicily (eclipse station), 53
Sidereal Messenger, 96
Smith, J. Lawrence, Fund, Committee,
99
Smith College, 106, 272
Smithsonian Astrophysical Observa-
tory, 257
Smithsonian Institution, 63, 67, 72,
257
Sociedad Astronomica de Mexico, 264
Solar eclipse, annular, 51
Solar eclipse, total, 8, 9, 12, 50, 51-52,
53, 54-55, 56, 61, 63, 67-68, 218
241, 244-245, 281
Solar neighborhood, 206
South African Association for the
Advancement of Science, 178
South African expeditions, 64-66
South Africa station of Harvard
College Observatory (see Harvard
College Observatory, Boyden Sta-
tion).
Southern Durchmusterung, 111-112
Southern Railways of Peru, 56
Southern station of Harvard College
Observatory (see Harvard College
Observatory, Boyden Station).
Spectral type, classification, 151-163,
248
Spectroscope, objective prism, 42,
149-150, 164
slit, 149-150, 165
Spectroscopic binary, Aurigae, 167
V Puppis, 167
M 1 Scorpii, 167
f Ursae Majoris, 166-167
Spectroscopy, 34, 42, 45, 118-119,
148-169, 240
aurora, 240
comets, 240
double stars, 166-167
nebulae, 240
novae, 164, 165-166
parallaxes, 167-168
variables, 164
Spring-governor, 38-39, 225
Stanford University, 272
Star clouds, 48
Stars, T Andromedae, 271
a Aurigae, 80
/3 Aurigae, 167
a. Bootis, 80
a Canis Majoris, 79, 80
8 Cepheii, 171
o Ceti, 171
X Cygni, 190
6 1 Cygni, 12
a. Geminorum, 116
a. Lyrae, 80, 116, 119
a Octantis, 129
6 Orionis, 194
Persei, 170, 171
r Puppis, 155
V Puppis, 167
/x 1 Scorpii, 167
a Ursae Majoris, 46, 117
f Ursae Majoris, 166-167
X Ursae Majoris, 46
g Ursae Majoris, 117
a Ursae Minoris, 116, 128, 129
W Virginis, 271
''Stellar Atmospheres," 74
Stellar systems, 198-213
Summerhouse hill, 25
Sumner line, 1 1
Sun, eclipses (see Solar eclipse).
brightness, 79-80
prominences, 79
SUBJECT INDEX
301
Sun, spectrum, 79, 81
spots, 26, 79
Survey of the Northeastern Boundary,
105
Thayer Professor of Physics (Massa-
chusetts Institute of Technology),
244
Themis, 90
Time service, 34, 241-242, 261
Titicaca, Lake, 59
plateau, 102
Toronto, University of, 271
Transit circle (see Harvard College
Observatory, instruments).
Transit observations, 51, no
Transneptunian planet, 91-92, 95, 269
Transparency of Earth's atmosphere,
85
Tufts College, 97
U
Union College, 271
United States Coast and Geodetic, 104
United States Coast Survey, 39, 51, 52,
53, 104, 222, 232, 241, 259, 260,
267
United States Geological Survey, 270
United States Lake Survey, 262
United States Naval Academy, 34, 239,
259
United States Naval Observatory, 34,
228, 238, 255, 257, 262
26-inch telescope, 231
United States Signal Service, 56, 102,
262
University Observatory, Oxford, 130
Uranometria Argentina, 124, 200
Uranometria Nova, 124, 129
Uranus, 11, 80, 87, 88
Variable stars, 36, 42, 45, 170-185, 263,
265, 269, 270, 271
classification, 170-171, 249
discovery from spectrum, 164, 248
distribution, 162
durchmusterung, 180
Harvard catalogues, 172, 267
nomenclature, 172-174
photometric observations, 134, 174-
175
standard magnitude, 175-176
(See also Cepheid variables, Cluster
variables, Eclipsing variables,
Long period variables.)
Vassar College, 106
Venus, transit, 6
photometry, 87, 88
Visiting Committee of Harvard College
Observatory, 19, 21, 104, 270, 284
Voigtlander lens, 119
W
Wadesboro (eclipse expedition), 63
Washington, Ga. (eclipse expedition),
63
Watson Gold Medal of the National
Academy of Sciences, 267
Wellesley College, 264
Williams College, 35, 258
Willows, Cal. (eclipse expedition), 56,
57
Worcester, Orange Free State, 65
Yale University, 85, 256, 272
Yerkes Observatory, 141, 165, 282
Variable Star Section of the British
Astronomical Association, 178,
Zodiacal light, 81, 92, ^59
ZSllner astrophotometer, 124, 125,
243, 260
