Read at the Congress of Astronomy and Astro-Physics, Chicago, August, 1893.

Mrs M Fleming.

In the earliest records of ancient Greek History we can trace the great interest which centres in the heavenly bodies, and in Astronomy, the greatest of all sciences, but in no way do we find women connected with the study of this science until a comparatively recent date. Caroline Herschel, Mary Somerville and Maria Mitchell were, as women, pioneers in this work. We cannot say these were the only women of their time capable of devoting themselves successfully to this work and of adding to our knowledge of the heavenly bodies and of the laws which govern them. Caroline Herschel and Maria Mitchell had rare opportunities afforded them, the former in that she had a brother who was thoroughly devoted to the work. Probably through him her interest was aroused and she became his assistant and his untiring companion in his researches. Maria Mitchell, in all likelihood, acquired a similar interest in Astronomy from her father, and her high standing as an astronomer is acknowledged by all connected with the study of this science. A great many women of to-day must have a similar aptitude and taste for Astronomy - and if granted similar opportunities would undoubtedly devote themselves to the work with the same untiring zeal, and thus greatly increase our knowledge of the constitution and distribution of the stars.

The United States of America is a large country, with a large-hearted and liberal-minded people. Here they have made room for comers from all other countries, have welcomed them and have given them a fair open field and equal advantages in pursuing their labours or studies, as the case may be. There is no other country in the world in which women, not as individuals, but as a class, have advanced so rapidly as in America, and there is no other country in which they enjoy the same unlimited freedom of action which affords them the opportunity to find their own level. In their studies they encounter very little narrow-mindedness or jealousy in their brother students or fellow workers in the same field of research, but in general they are treated with the greatest courtesy, encouragement and assistance being graciously accorded. Women, therefore, who have taken up any branch of science, or indeed work of any kind, need not be discouraged in it even if one or two of the great mass which goes to make up the whole in their superior judgment refuse to give credit to their work. Labour honestly, conscientiously and steadily, and recognition and success must crown your efforts in the end.

Photography, as applied to Astronomy is one of the greatest advances which has been made in this the oldest of sciences, and this same advance has opened up a comparatively extensive field for woman's work in this department. Dr Henry Draper of New York was the first scientist who photographed successfully the lines in a stellar spectrum. His wife, Mrs Anna Palmer Draper, was his constant companion and assistant in all his experiments and researches. On the interruption of his valuable investigations by his sudden death in 1882, Mrs Draper, knowing the great value of the work already done, decided that the investigations should be continued at the Harvard College Observatory under the direction of Professor Edward C Pickering, and she set aside a liberal sum of money to be used for this work, thus founding the department known as "The Henry Draper Memorial." In 1886 there were three women computers engaged in the work in this department; at the present day there are twelve women engaged in the same or in similar work. Miss Catherine W Bruce of New York has shown her appreciation of the photographic work now being carried on at the Harvard College Observatory by her generous gift to that institution of $50,000 for the erection of a photographic telescope of the largest size. The Observatory has a corps of about forty assistants, seventeen of whom are women, and twelve, as stated above, are engaged, more or less, on the photographic work.

The photographs obtained with the various telescopes now in use at the Harvard College Observatory in Cambridge, and at the auxiliary station near Arequipa, Peru, are of various classes, the most important of these being chart plates having exposures of from ten to sixty minutes or more, spectrum plates having exposures of from ten to sixty minutes, and trail plates having several exposures of a few seconds duration. The women assistants are not engaged during the night in taking these photographs but find their time during the day sufficiently occupied in examining, measuring, and discussing them, and in the various computations therein involved. Catalogues, for reference, of the plates taken with each instrument have to be kept up to date, the plates have to be compared with the charts of the part of the sky which they are supposed to represent, in order to check the correctness of the record made by the observer, and to ascertain that the region intended is contained on the plate. The chart plates are then filed carefully away and are used in the confirmation of variable stars or other interesting researches. The most important work at present being done from the chart plates taken with the 8-inch Draper telescope in Cambridge, and with the 8-inch Bache telescope in Peru, is the measurement of the faint stars for standards of stellar magnitudes. These measurements of about forty thousand stars are now being made by Miss Eva F Leland. She is also engaged in the measurements of the brightness of the stars in clusters. Miss Louisa D Wells and Miss Mabel C Stevens have shown great skill and accuracy in making the identification of stars shown in the photographs, with those contained in existing catalogues. The photographs of stellar spectra are all carefully examined in order to detect new objects of interest, such as third type stars, fourth type stars, fifth type stars or those, whose spectra consist mainly of bright lines, and similar to those discovered in Cygnus by Wolf and Rayet, planetary nebulas, and variable stars. All of these except the first named class differ so much from the general mass of stellar spectra, that a trained eye has little difficulty in detecting them on the photographic plates, even although the objects found are sometimes as faint as the ninth magnitude. If an object is detected on any of the photographs showing a spectrum of the third type, having also the hydrogen lines bright, it is at once suspected of variability, since only variables of long period are known to possess this peculiarity. The catalogues of the plates taken with the different instruments are then consulted, and a list is made of all the plates covering the region of the star suspected of variability. So you have, ready to your hand and for immediate use, the material for which a visual observer might have to wait for years and certainty for months. This material must also be considered more reliable, for in the case of a visual observer, you have simply his statement of how the object appeared at a given time as seen by him alone, while here you have a photograph in which every star speaks for itself, and which can at any time, now or in the years to come, be compared with any other photographs of the same part of the sky.

Many interesting discoveries have been made from the study of these photographs of stellar spectra. First in importance among them, was the discovery that Ursae Majoris is a close binary star, the two components revolving around each other at a velocity of about a hundred miles a second, in a period of about fifty-two days. This discovery was made by Professor Edward C Pickering, his attention being first attracted to it by the fact that in the photographs of the spectrum of this star, the lines appear sometimes double and at other times single. This discovery led to the finding of a second object of this same class, β Aurigae, by Miss Antonia C Maury. This last star has attracted public attention much more widely than Ursae Majoris and may be considered more interesting in that the period of revolution of the two components is only 3 days 23 hours and 36.7 minutes. Ursae Majoris and β Aurigae are such close double stars that they could not possibly be separated visually with the most powerful instruments at present in use. A third object of this class is suspected in β Lyrae which shows a similar change, or rather it shows a reversal in the position of the bright lines with regard to the dark lines in its photographic spectrum, that is, they apparently cross and re-cross each other. This is doubtless associated with the variation in the light of this star since the period is the same for both. The examination of the photographs of the brighter stars has been made by Miss Maury who has also been engaged on their classification. The micrometric measurements of the lines in the photographic spectra of the bright stars have been made by Miss Florence Cushman.

From the examination of the photographs of stellar spectra, thirty-eight stars having spectra of the fifth type have been added to the sixteen previously known, making the known number in all fifty-four. Three of the stars in this list have been discovered during the past few days and have not as yet been announced elsewhere. Twenty-three new variable stars have been discovered in this same examination of the photographs, and before being published each and all were confirmed by Professor Pickering. Two of the twenty-three have not yet been announced elsewhere since one of them was discovered only yesterday. This star is in the wonderful southern cluster ω Centauri, the finest in the sky, and being so situated would probably never have been discovered by other means than photography. The other star is in Columba and is the first variable discovered in that constellation. Its position for 1875 is in R. A. $5^{h}45^{m}41^{s}.9$, Dec. -29° 13'.7.

One must not always cling to the earliest method of accomplishing anything and assume that because it was the earliest and has held sway for centuries, it must consequently be the best, and also the only way. Where should we be today if we did not advance steadily in all things? Taking light for instance, first we have rude torches and rush lights, then candles by which the day was measured off into hours, this followed by lamplight, later by gaslight, till now we have electricity to light our streets and our dwellings. And powerful as electricity is in itself for all purposes to which it has been applied, who among us can say that in it we have attained the highest degree of perfection in illumination? So it is with everything else we may take up, and so it is with astronomy. And thus while the old time astronomer clings tenaciously to his telescope for visual observations, astronomical photography is leaving him far behind and almost out of the field in many investigations which nevertheless he still continues in his own way, trying also to maintain that, as stated above, it must be the best, if not the only way. If photographic work is to be entirely ignored by the astronomers of the old school as they may be called, because, as they themselves say, they have no knowledge of photography, and not having the means at their command, do not wish to acquire a knowledge of it, what is to become of the researches planned and undertaken by the Astro-Photographic Congress of Paris, in which astronomers of all countries have united? We may safely say that the younger, more advance guard of civilisation will uphold photography and encourage it as applied to astronomy, as in other scientific researches in which it is also successfully employed.

A new variable star in the constellation Delphinus was discovered from the photographs some time ago, and was announced in "The Sidereal Messenger," Vol. X, p. 106. Two skilled visual observers undertook to observe it in order to confirm, or refute, its variability. One arrived at the conclusion that it was not variable and was always about the ninth magnitude, while the other also found that the star was not variable, but according to his observations it was always about the eleventh magnitude. When they met together to discuss this difference in magnitude, they discovered that each had been observing a different star, and further, that neither of them had observed the variable. No such error could have occurred from the comparison of the photographic charts.

Unlike telescopic observations, the photographs are available always, at any time during the day or night, for consultation and examination. Therefore, while an observer with a telescope, be it even the most powerful that can be made, is at the mercy and dependent upon the state of the weather for his observations, the discussion of the photographs goes on uninterrupted and is undoubtedly much more reliable than visual work, since when a question of error in observation arises, anyone interested in the research can, at any time, revise the original observation by another and independent examination of the photograph.

Given the instruments, and materials required, with a knowledge of how the instrument is used, you can obtain in one night what would represent years of hard labour in visual observation, and in the necessary computation involved in reducing and charting these same observations. Even when finished the visual observer's chart may be subject to various errors in the positions or in the brightness of the stars with which he has dealt, but the photograph cannot fail to be an exact and unquestionable record which can be consulted and compared with others years hence, and thus serve to prove or disprove variations in light, changes in position, and in the case of the spectrum plates, changes, if any, in the constitution of the stars. Thus on a photographic plate, on which it has taken only a few minutes to reproduce the portion of the sky covered, you have a true chart of the stars in that part of the sky at that time, the limiting magnitude being dependent on the duration of the exposure and also on the sensitiveness of the plate used.

In a catalogue of variable stars recently published and entitled "Second Catalogue of Variable Stars," a more correct title would be "Second Catalogue of Variable Stars discovered Visually," since in it no weight is given to photographic observations further than is necessary to enable them to swell the list of stars discovered visually. Stars discovered photographically which have been announced as variables, and have been proved beyond doubt to be variables, are here credited as "suspected."

In conclusion, while I may be thought to have strayed far afield from the subject on which I was supposed to address you here, the investigations and researches described above are those in which the women in this department are engaged, in which they are thoroughly interested, and in which they are becoming trained and competent assistants.

While we cannot maintain that in everything woman is man's equal, yet in many things her patience, perseverance and method make her his superior. Therefore, let us hope that in astronomy, which now affords a large field for woman's work and skill, she may, as has been the case in several other sciences, at least prove herself his equal.

Harvard College Observatory,
Cambridge, Mass., August 4, 1893.

By Mrs M Fleming.

It is impossible at any one spot on the surface of the earth to establish an observatory at which all the stars in the sky can be observed. Even at the equator where all stars are visible, accurate measures could not be obtained of the stars in the vicinity of the poles since they are too near the horizon. Thus at the Harvard College Observatory while the horizon is in declination -47° 37', stars south of -30° cannot be satisfactorily measured, neither can good photographs of them be obtained. Several important investigations which are described below having been undertaken at Cambridge and satisfactorily completed for the northern heavens, it was considered of great importance that these researches should be extended to the southern sky. Plans were therefore made for an auxiliary observing station in the southern hemisphere, and they have finally resulted in the erection of a collection of buildings, consisting of a dwelling-house for the observers, and various shelters for the different instruments, about three miles northwest of Arequipa, Peru, at an elevation of about 8000 feet. Here all arrangements have been made for extending to the south pole the researches begun at Cambridge.

The results of the first investigation undertaken as a memorial to Dr Henry Draper are contained in the H. C. O. Annals, Vol. XXVI, part I and Vol. XXVII. The first of these volumes contains a catalogue of the photographs of the stars taken at Cambridge and at Willows, California, and a discussion of the results of the measures made from these plates. The measures themselves form the Draper Catalogue of Stellar Spectra and are contained in Vol. XXVII. The photographs were taken with the Bache telescope whose objective is a photographic doublet having an aperture of eight inches and a focal length of forty-five inches. A prism having a refracting angle of 13° was placed in front of the objective and thus the spectra of all stars in the field of the telescope were obtained on the photographic plate. The plates used were the most rapid 8 × 10 SEED plates, and each plate covered a region 10° square. Nearly the entire sky north of -30° was photographed here, four different investigations having been undertaken with the above-named instrument. First, chart plates having $10^{m}$ exposure; second, chart plates having $60^{m}$ exposure; third, spectrum plates having $10^{m}$ exposure; and, fourth, spectrum plates having $60^{m}$ exposure. The spectrum plates having $10^{m}$ exposure were those measured for the Draper Catalogue. They show the spectra of nearly all the stars brighter than the sixth magnitude.

When the last two investigations mentioned above were nearly completed the instrument was removed to California, where it was mounted at Willows and used in photographing the Solar eclipse of January 1, 1889. The photographs obtained with the Bache telescope in the northern hemisphere being so satisfactory, it was decided that the investigations undertaken with it should be extended to the south pole. Accordingly, in the spring of 1889, an expedition under the direction of Mr S I Bailey, started for Peru. Owing to the scarcity of wood in that country two frame houses were constructed here, one for the shelter of the instruments, the other for the observers. These were successfully erected on a mountain (since then known as Mount Harvard) about 6500 feet high, near Chosica, and about twenty miles east of Lima, Peru. The observers were thus almost entirely cut off from communication with the world below, and all supplies, even including water, had to be carried by mules from the valley below, a distance of about eight miles. The photographic work at this station was similar to that of the Cambridge station, except that the portion of the heavens to be photographed was from -20° to the south pole. In other respects the plans for the four investigations described above were the same. The weather proved entirely satisfactory during the first six months. Fogs and clouds which often covered the adjacent valleys and the city of Lima did not reach to the top of the mountain. About thirteen hundred photographs were obtained and each of the four principal researches described above was one-half completed. The rainy season then set in, and during it the observers visited other points of the coast going as far south as Valparaiso, to look for a better location. After visiting many different places they decided that the climatic conditions at Arequipa, which is situated on the Mollendo railway at an elevation of about 7500 feet, were the most favourable for the continuation of the work planned for the southern station.

In addition to the photographic work another investigation was conducted at the station on Mount Harvard. All the stars north of -30° of the magnitude 6.0 and brighter, as also the stars brighter than the tenth magnitude used for comparison with variables, and the zones used in the photometric revision of the Durchmunsterung were measured at Cambridge with the meridian photometer. When Mr Bailey went to Peru he took this instrument with him in order to extend the above investigations to the south pole. He obtained 217 series of observations containing 98,756 photometric comparisons of about 8000 southern stars. This work, together with the results published in Vol. XIV and XXIV, will furnish photometric magnitudes of stars as bright as the ninth magnitude in all parts of the sky. The stars selected for measurement in Peru include all those of the sixth magnitude and brighter south of -30° and all known stars in a series of zones 20' wide at intervals of 5° in declination from -25° to -80°, also all known stars south of -80° and a miscellaneous list of variables, etc. The reduction of these observations is nearly completed and their publication will be begun shortly. While looking for a better location for the southern station, Mr Bailey took with him the meridian photometer, and obtained some valuable observations with this instrument at Pampa Central, in the Desert of Atacama, which was selected for the dryness of its climate. In October, 1890, the instruments on Mount Harvard were again dismounted and conveyed to Arequipa.

Photographs of planets, double stars, clusters, nebulae and other objects of special interest had meanwhile been obtained with the 13-inch Boyden telescope at Cambridge and at Mt Wilson in Southern California. Another expedition was accordingly planned which provided for the removal to Arequipa of this telescope with several smaller instruments. On December 20, 1890, Professor Wm H Pickering sailed from New York for Arequipa, Peru, accompanied by his assistants, Mr A E Douglas and Mr R D Vickars. They joined Mr Bailey at Arequipa, Professor Wm H Pickering assuming charge of the station while Mr Bailey, having completed his observations with the meridian photometer, returned to Cambridge, bringing with him that instrument and leaving the Bache photographic telescope where it is still used in completing and extending the investigations described above. Very favourable accounts of the atmospheric conditions at this station have been received. The sky is nearly cloudless during the greater part of the year, the air is remarkably steady, the images of the stars are small and round, and even using high powers, the fluctuations of the images are very slight. Several diffraction rings are visible around the brighter stars. They are rarely seen at Cambridge with so large an instrument. Therefore, at this station, the limit of observation will depend on the size of the instrument used instead of, as at other observatories, the condition of the air. It therefore seems to be of great importance to astronomy to have at this station a large and powerful telescope, one which would give results for the southern heavens, which would be comparable with those of the northern heavens, obtained with the Lick telescope.

The Boyden telescope has an aperture of only thirteen inches, and yet it is apparently the largest refracting telescope in use in the southern hemisphere, or in fact south of +35°. In addition to the study of the objects of special interest mentioned above, a plan has been made for photographing with this instrument, the spectra of all the brighter stars in the southern heavens by placing in front of the object-glass one of the prisms which was formerly used with the 11-inch Draper telescope. Photographs have been obtained at Arequipa showing the extreme ultra-violet lines including a series of lines or bands of even shorter wavelength. Thus the detailed study and classification of the brighter stars, also, will be extended to the South Pole. In fact, almost all the more important investigations undertaken at Cambridge are, by means of this valuable auxiliary station, being rapidly extended from pole to pole. Meteorological instruments are in operation at this station and will furnish interesting records of atmospheric conditions prevailing at this elevation. A series of meteorological observations at Vincoucaya, elevation 14,600 feet; at Peru, elevation 12,500 feet; and at Mollendo, near the sea level, have also been obtained. An ascent of El Misti, which has an elevation of 18,600 feet, was made by Professor Wm H Pickering

Another interesting expedition was that to Tiahuanuco and the sacred islands of Incas, on lake Titicaca, which led to results of much archaeological interest. Important aid has been rendered to the expedition by many residents in Peru without whose assistance the establishment of the station would have been extremely difficult.

Harvard College Observatory,
Cambridge, Massachusetts, February 19, 1892.

Before giving the excerpts, let us note that at the time she wrote this her son Edward Pickering Fleming was 20 years old and Annie Cannon was lodging with both Mina and her son at 273 Upland Road, Cambridge, Massachusetts. We also note that Mina was suffering from repetitive strain injury due to the work she was undertaking.

March 1, 1900:

In the Astrophotographic building of the Observatory, 12 women including myself are engaged in the care of the photographs; identification, examination and measurement of them; reduction of these measurements and preparation of results for the printer. The measurements made with the meridian photometers are also reduced and prepared for publication in this department of the Observatory. From day to day my duties at the Observatory are so nearly alike that there will be but little to describe outside ordinary routine work of measurement, examination of photographs, and work involved in the reduction of these observations. My home life is necessarily different from that of other officers of the University since all housekeeping cares rest on me, in addition to those of providing the means to meet their expenses. My son Edward, now a junior in the Massachusetts Institute of Technology, knows little or nothing of the value of money and, therefore, has the idea but that everything should be forthcoming on demand. The first part of this morning at the Observatory was devoted to the revision of Miss Cannon's work on the classification of the bright southern stars, which is now in preparation for the printer ... several pages of the remarks on the individual stars were read, criticised, corrected or questioned.

March 2:

This day of Observatory work, beginning at 9:15 a.m. and ending at 6:00 p.m. has been devoted to miscellaneous odds and ends and a gathering together of loose strands. The early part of the morning was occupied with scientific correspondence and in sending out copies of "Standards of Faint Stellar Magnitudes", No. 2, to those who are expected to take part in the work of securing observations. Next in order came the remarks on Miss Cannon's Classification of Spectra. This is very trying work as so many things have to be taken in to consideration, especially while it is found necessary to change the form of a remark.

Many other pieces of work were also discussed, among them the measurements of Algol variables on plates taken with the variable star apparatus. The Director favours turning this work over to some assistant in the laboratory who has never undertaken any work of this kind. It is work which requires a thorough knowledge of the sequences comparison stars for each variable, and as a large number of images of each star appears on every plate the task of identifying the comparison star in the same exposure as the variable is generally extremely difficult, and requires considerable skill and patience. Therefore, I proposed leaving these measures in the hands of Miss Leland, who, like myself, has had considerable trouble with them already.

March 3:

Another full day at the Observatory from 9:00 a.m. to 6:00 p.m. Part of the morning I spent with Miss Cannon, discussing the remarks on her classification, and explaining the reasons why we had changed one thing and questioned another ... Later in the afternoon I noted a few more interesting objects, among them, two fourth type stars, one gaseous nebula and several bright lines stars. Some of these may be new. Looking after the numerous pieces of routine work which have to be kept progressing, searching for confirmation of objects discovered elsewhere, attending to scientific correspondence, getting material in form for publication, etc., has consumed so much of my time during the past few years that little is left for the particular investigations in which I am especially interested. The Director, however, says that my time employed in the above work is of more value to the Observatory so I have delegated my measures of variables, etc., to Miss Leland and Miss Breslin.

March 4 [Sunday]:

This is my day of rest and retirement so far as Observatory work is concerned.

March 5:

If one could only go on and on with original work looking for new stars, variables, classifying spectra and studying their peculiarities and changes life would be a most beautiful dream; but you come down to its realities when you have to put all that is most interesting to you aside, in order to use most of your available time preparing the work of others for publication. However, "whatsoever thou puttest thy hand to, do it well." ... I am more than contented to have such excellent opportunities for work in so many directions, and proud to be considered of any assistance to such a thoroughly capable scientific man as our Director.

March 12:

I had some conversation with the Director regarding women's salaries. He seems to think that no work is too much or too hard for me, no matter what the responsibility or how long the hours. But let me raise the question of salary and I am immediately told that I receive an excellent salary as women's salaries stand. If he would only take some step to find out how much he is mistaken in regard to this he would learn a few facts that would open his eyes and set him thinking. Sometimes I feel tempted to give up and let him try some one else, or some of the men, in order to have him find out what he is getting for $1500 a year from me, compared with $2500 from some of the other assistants. Does he ever think that I have a home to keep and a family to take care of as well as the men? But I suppose a woman has no claim to such comforts. And this is considered an enlightened age! ... I feel almost on the verge of breaking down.