ARTICLE XIII.

It shall be the duty of the Directors, in case any circumstances shall arise likely to endanger the harmony, welfare or good order of the Society, to call a special meeting of the Society; and if, at such meeting, after an examination of the charges, and hearing the accused, who shall have personal notice of such proceedings, it shall be proposed that the offending member or members shall be expelled, a vote by ballot shall be taken, and if two-thirds of the members present vote in favor thereof, the offending member or members shall be expelled.

ARTICLE XIV.

The Directors shall meet half an hour before the stated time of each bi-monthly meeting, and at such other times as they may appoint. The President, or, in his absence, any one of the VicePresidents may call special meetings of the Board of Directors at any time. Notice of the time and place of such meeting shall be given by the Secretaries, by depositing in the post-office at San Francisco a notice of the time and place, addressed to each Director personally, at his last known place of residence, with the postage thereon prepaid, six days before the time of meeting.

ARTICLE XV.

The By-Laws may be amended at any time by a consenting vote of nine members of the Board of Directors at any duly called meeting thereof.

ARTICLE XVI.

In order to increase the usefulness of the Society, any groups of its members residing in the same neighborhood (except in the City and County of San Francisco, State of California) are authorized to form local organizations which shall be known as "The Section of the Astronomical Society of the Pacific."

No section shall be formed except by the consent of the Board of Directors of the parent Society.

The proceedings of such sections may be printed in the Publications of the Astronomical Society of the Pacific, either in full or in abstract, and the parent Society shall not be in any way responsible for publications made elsewhere.

No person not a member of this Society in good standing shall be eligible to membership in a section, nor shall membership in a

section interfere in any way with the status of the person as a member of this Society.

The special expenses of each section shall be borne by the group of members composing it, and this Society shall not be liable for any debts incurred by any section.

NOTICE OF DR. DREYER'S BIOGRAPHY OF TYCHO

BRAHE.

BY TORVALD KÖHL,

The Director of the Armagh Observatory in Ireland, Dr. J. L. E. DREYER, whose native country is Denmark, has not long ago written an excellent work under the title: TYCHO BRAHE, A Picture of Scientific Life and Work in the Sixteenth Century. 8vo. It has been published by the Editors ADAM and CHARLES BLACK in Edinburgh and appears, as might be expected from that firm, in a very nice shape. The work is dedicated to RALPH COPELAND, the distinguished Astronomer Royal for Scotland, a friend of the author, and consists of xvi +405 pages.

The book is prettily illustrated by several woodcuts, representing: Hveen at the time of TYCHO BRAHE; Uraniborg and Grounds; Uraniborg from the East; Plan of the Ground Floor of Uraniborg; Stierneborg, seen from the West; Plan of Stierneborg; The Tychonic System of the World; Gemma's Astronomical Ring; Armillæ a Equatoria Maximæ; Sextans Trigonicus; Transversal Divisions. Besides the likeness of TYCHO BRAHE, found in England in 1876, the work contains some superb reproductions of photographs: Mural Quadrant; Castle of Benatky; Villa of FERDINAND I; Tomb of TYCHO BRAHE.

Dr. DREYER is building on a deep study of the works of TYCHO BRAHE and knows to the least details all that has been written about the famous Danish astronomer. The book is brightly written and we confidently recommend it to the members of the Astronomical Society of the Pacific as being of great historical interest. With much ability the author guides the reader through the dark age in which the "reformer of observational astronomy" dwelt on our planet.

After having treated "The Revival of Astronomy in Europe" the author gives an interesting description of TYCHO BRAHE's

youth. It is pretty well known how the heaven itself claimed the attention of the young TYCHO. "On the 21st of August, 1560, an eclipse of the sun took place, which was total in Portugal, and of which CLAVIUS has left us a graphic description. graphic description. Though it was only a small eclipse at Copenhagen it attracted the special attention of TYCHO, who was then only 14 years old. When he saw the eclipse take place at the predicted time it struck him as something divine that men could know the motions of the stars so accurately that they could long before foretell their places and relative positions."

But the lively mind of the young student was soon drawn in other directions, and from the 30th day of December, 1570, till November, 1572, we do not possess a single astronomical observation made by TYCHO BRAHE, while during this time he worked with great energy at chemical experiments; and now a most unusual and startling celestial phenomenon was necessary to rouse him to renewed exertion and show him his real position in future as a diligent laborer in astronomy. This phenomenon was the appearance of the new star of 1572.

In a most attractive manner Dr. DREYER tells this important chapter of the great astronomer's life.

Perhaps any one may think that too much space in the following chapters has been devoted to the consideration of the astrological fancies of the Middle Ages; but doubtless the author is right when he in the Preface, with regard to this point, states: "If the study of the history of science is to teach us anything, we must make ourselves acquainted with the by-paths and blind alleys into which our forefathers strayed in their search for truth, as well as with the tracks by which they advanced science to the position in which our own time finds it."

The author attains his purpose which is to let the reader feel the same veneration for his hero as he feels himself, and he succeeds in distributing praise and blame in a moderate and wise manner. Of course the contest resulting in TYCHO BRAHE'S departure from his native land, to which he never returned, has been treated with much extension in the chapter on "The last years at Hveen, 1588-1597." From these earthly troubles it is encouraging to turn to the celestial works of that time. The improtance of TYCHO BRAHE'S scientific fights and victories has been inculcated in a drastic manner by the apparently so singular words, p. 175: "The Copernican System as set forth by

COPERNICUS, therefore, did not advance Astronomy in the least; it merely showed that it was impossible to calculate the motions of the planets without having the origin of the co-ordinates in the centre of the earth. But of proofs of the physical truth of his system, COPERNICUS had given none, and could give none; and, though there can hardly be any doubt that he himself believed in the reality of the earth's motion, it is extremely difficult to say of most of his so-called followers whether they had any faith in that motion or merely preferred it for geometrical reasons.

Though against his own wishes TYCHO BRAHE has contributed very much to the success of the Copernican system, for the numerous and most accurate observations made by the Danish astronomer on his little island in the Sound between Seeland and Scania are the source, from which JOHANNES KEPLER deduced his renowned laws. "ARCHIMEDES of old had said, 'Give me a place to stand on, and I will move the world?' TYCHO BRAHE had given KEPLER the place to stand on, and KEPLER did move the world!" On his death-bed the great observator several times exclaimed:

"Ne frustra vixisse videar!"

His death occurred on the 24th day of October, 1601. The future will bear witness that he did not live in vain.

As his countryman, I allow myself to congratulate the author, thanking him heartily for his excellent work.

ODDER, DENMARK, 1891, April 15.

THE PERIOD OF THE ROTATION OF THE SUN
NEAR THE POLES, AS DERIVED FROM
THE CORONAS OF 1878 AND 1889.

BY PROFESSOR FRANK H. BIGELOW.

In the American Journal of Science for November, 1890, the formulae for discussing coronas, and the results obtained by a study of the photographs taken during the eclipse of July 29, 1878, were presented and fully explained. In this paper the conclusions and the deductions to be derived from the coronas of Jan. 1, 1889, and Dec. 22, 1889, are added, with the period of the rotation of the Sun as found from these three coronas.

The following tables summarize the data in the briefest form. Column I shows the number of rays which were measured on the photographs.

Columns 2 and 3 give the polar co-ordinates of each point of the ray, at least three points being measured, the first near the disk, the second at a mid point, and the third near the visible extremity of the ray. The axis of reference was taken by setting the thread on the projected ray whose trace had a radial direction from the centre of the disk.

The column a gives the angle between the plane of the ray and the plane of the disk, which is taken as the plane passing through the centre of the sun at right angles to the line of sight. Strictly, the planes of the coronal rays intersect in an axis which does not coincide with the plane of the disk, and a slight error is admitted by assuming provisionally that it does. It is one object of our investigation to discover the angular distance between the pole of the corona and its trace.

Using all values of (r.)

we obtain three values of a. The adopted value is given in the table.

The column gives the angle from the coronal pole at which each ray springs from the surface of the sun, in the direction a from the plane of the disk, the results being computed for each point of the ray. If the angle a is inaccurate the values of 0, will progress in one direction, and hence a check is obtained for the adopted a. At this step a second computation is frequently required. The outstanding irregularities arise from the difficulty of setting the measured points of the photograph on the true stream lines of the corona.

where x and y have three values in order.

The columns r', '

give the co-ordinates in space of the point whose projected position we see on the photograph. We present only that corres