Morse's Landmarks In Astronomy.—Mr. E. P. Morse, of Batavia, New York has prepared a neat 9-inch star map which is printed on white card board, arranged with colored cords for marking the day, the meridian, the zenith, etc. The map shows the Milky Way, the constellations in faint outline and prominent stars in true positions, the ecliptic, daily motion of the Sun, and other useful elementary data. It is so easily under stood that it ought to be a thing of use and pleasure in the hands of a child a dozen years old, because with it he may locate any prominent star, or to tell the time of night by the stars. Price 25 cents.
BOOK NOTICES.
A Popular History of Astronomy During the Nineteenth Century by Agnes M. Clerke. Publishers, Messrs. Adam and Charles Black, Edinburg, Scotland, 1885, 8vo, pp. 468. This book is a genuine surprise because of its merit and its
timely appearance, and because it was not written by a man;
for the years are few since the time that a woman either could or would have written a book on astronomy for popular reading in Europe or America, because the savants would have thought such an undertaking strangely unorthodox according to any scientific creed.
But ideas have changed somewhat since the time of Caroline Herschel and Maria Mitchel (now of Vassar College Observatory) and the doors of Science open more easily and naturally to merit and skill, in any person, than they were wont to in earlier days.
To write a history of astronomy to follow such an author as Grant, which shall clearly present its marvellous growth, in all the varied and intense specializations of work, in the nineteenth century, is indeed a task that few astronomers in the world would not hesitate to undertake.
In the midst of such difficulties Miss Clerke has gathered the materials of this book and written it admirably. The theme is divided into two parts, the first treating of the progress of astronomy during the first half of the nineteenth century, and the second is a critical review of the recent progress of the science. Under the first head, the work of Sir William Herschel appears justly as the foundation of Sidereal Astronomy, on which the noted Bessel begins to build exact astronomy in Germany. The skill of Fraunhofer is a useful adjunct at this time, and Struve's double-star researches and Sir John Herschel's explorations of the heavens are some of the characteristics of fifty years of progress in astronomy. Under the same head, are also presented the progress of knowledge regarding the Sun, planetary discoveries, comets, and instrumental advances.
About two-thirds of the book is devoted to the recent progress of astronomy, commencing with the foundation of astronomical physics, as seen in the discovery of the sun-spot period, magnetic disturbances and the elementary principles of spectrum analysis, the theory of the constitution of the Sun, solar photography, planetary influences. Then follows specialized study in recent solar eclipses, the spectroscopic study of the the Sun, the temperature of the Sun, its distance, planets and
satellites, theories of planetary revolution, recent oomets, stars and nebulae, and methods of research.
From a careful reading of this book, it would seem froni the form of expression, now and then chosen, that the authoress has not been a practical observer, and yet we can but admire the skill with which she freely and independently discusses impending problems of the science. We do not say that we fully endorse all positions taken as quite eatisfactory; for example, the claims regarding the discovery of Neptune, the theory of the solar corona, spectroscopic work, the personal equation, etc., but all these points and others in mind, are minor matters, which will neither seriously disturb or mislead any body. The fresh, apt and terse way, in which the good things of every page are said to overshadow the weak ones that they are scarcely noticeable.
We have read this book with delight, and in commending it to the readers of the Messenger we bespeak for it unusual favor in Ameriea.
A Catalogue of Suspected Variable Stars. With Notes and Observations. By J. E. Gore, M. R. T. A., F. R. A. S.
This catalogue of suspected variable stars was presented as a paper before the Royal Irish Academy in 1884, and reprinted from its proceedings. It contains 158 pages of closely printed matter with a frontispiece double-page plate showing the distribution of known and suspected variable stars, the known being red dots, while the suspected are black ones. The catalogue proper is arranged in six columns, on the page, first, the number of the star, second, its name; third and fourth, R. A. and Declination for 1880; fifth, supposed change of magnitude, and sixth, authority. Whole number of stars is 773, taken in order of right ascension. The notes accompanying are unusually full and apparently prepared with care and great labor.
The Catalogue is a valuable and needed contribution to this new branch of astronomy.
The new Minor Planets, recently discovered by Dr. Palisa, fire numbered respectively 254, 255, 256, 257.
CONDUCTED BY WM. W. PAYNE,
Director of Carleton College Observatory, Xorthfleld, Minnesota,
"In the present small treatise I set forth some matters of interest to all observers of natural phenomena to look at and consider."—Galileo, Sidereus Nuncius, 1610.
Vol. 5. No. 6. JUNE, 1886. Whole No. 46.
DESCRIPTION OF A PRINTING CHRONOGRAPH.
PROF. G. W. HOUGH, Director Op Deaerobn Observatory.
About the year 1848, the idea of recording astronomical observations, by the use of galvanic electricity, was put in successful operation by different individuals. Since that time chronographs of various forms have been constructed for recording in a legible manner, on a moving sheet of paper, the time of any phenomenon observed. The great superiority, in point of accuracy and saving of labor over the old eye and ear method, formerly used, soon led to the general adoption of the new plan.
The idea that type-wheels might be substituted for the moving paper, and a printed record made, was long ago entertained by astronomers, and various plans were devised for accomplishing this purpose.
In the year 1865, in a paper read before the Albany Institute, I gave an outline of a plan for a printing chronograph, radi3ally different from any that had been proposed. It was based on the principle of using separate systems of mechanism for the fast running type-wheel, and those recording the integer minutes and seconds. These two trains to be simultaneously controlled by the sidereal clock, and to be entirely independent of each other.
In the year 1871 I completed a printing chronograph based on this method.
This machine was in constant use at the Dudley observatory for three years, demonstrating the practicability of such an apparatus.'
In this first machine the blow for printing was done by a hammer, elevated by a heavy train of clock-work, which made the instrument somewhat unwieldy. The type-wheels were constructed
by soldering electrotype strips, on the rim of a brass disc, and required to be renewed once a year or oftener. In other respects the machine was entirely satisfactory.
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