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companies this article one can pretty certainly locate the moving star, which is easily and certainly determined in a few minutes by the aid of the micrometer wires and known adjacent stars. For the aid of those who may not have seen a chart containing the orbits of the Earth, Mars, Eros and Jupiter we re-print one

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herewith that was used in October 1898, when the planet was

called DQ, and before it was named Eros.

At another time more will be said of the details of both the photographic and the micrometric methods of determining the parallax of Eros.

RECENT WORK AT THE LOWELL OBSERVATORY.

W. W. PAYNE.

We have received Volume II of the Annals of the Lowell Observatory, the observations of which were made at Flagstaff, Arizona, and Tacubaya, Mexico, on Jupiter and his satellites in 1894 and 1895 and on Mars in 1896 and 1897. In July 1896, Mr. Lowell, the director of the Observatory received from Alvan Clark and Sons the new 24 inch telescope with which the astro

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nomical work of the Observatory was continued as mentioned above. In the completion of this telescope, utting it in place in the Observatory, and in adjusting it, Mr. Alvan G. Clark was much interested, as those who were present at the time very well know, and they speak of it really as his last work in the line of telescope-making. Those who have used this noble instrument are unsparing in praise of its fine-even its superb qualities.

In November of this year the entire Observatory was removed to Tacubaya, a suburb of the city of Mexico, where it remained until the end of March 1897, at which time it was removed again to Flagstaff where it has since remained.

In the Annals so far published, Volume I gives the complete work on Mars in the years 1894 and 1895. The volume before us "completes the strictly astronomical work of that year by giving that done on Jupiter and its satellites." The volume also commences the publication of subsequent work with the 24-inch instrument by presenting that on Mars in the second observational year, and the third year of the Observatory. This volume is therefore occupied with work relating to two objects: Mars and Jupiter and its satellites.

The observations on Jupiter in 1894 were made by William H. Pickering and those in 1895 by A. E. Douglass. Together they make the first long series of physical observations of the planet Jupiter and its satellites known to us. In this statement we do not forget the long, skillful and painstaking work of Professor G. W. Hough, of Dearborn Observatory, now of Evanston, Ill., who for more than twenty years, has been giving more or less attention to the surface markings of Jupiter, and who is estemeed a high authority, by astronomers generally, in relation to the physical characteristics of the planets.

The larger part of the work on the Jovian system in this was done by William H. Pickering, whose methods of research in 1895, were especially well adapted to gain the information desired. Later it fell to Mr. A. E. Douglass to carry through the mathematical part of this work by his own methods, yet with the consent of Professor Pickering. One peculiarity is noticeable in these observations and that is, that they are given complete in the original form in which they were made. The reasons assigned are two: one, because they are the first extensive, systematic study of the kind ever made, and second, because in most of the work the observer and the reducer were two different persons, and the equations of each enter into the results.

The observations of Mars were made by Mr. Lowell, the

Director, assisted by Mr. D. A. Drew, Miss W. L. Leonard and Mr. A. E. Douglass. Dr. T. J. J. See and Mr. W. A. Cogshall were also members of the Observatory, and made occasional observations. Mr. Douglass did, or had charge of, the reductions and the analytic study, save the tables of diameters by Mr. Lowell and such short preliminary articles as have been previously published by other persons belonging to the Observatory.

This quarto volume consists of 523 pages and, in general appearance is like the Harvard College Observatory Annals.

One distinguishing feature in addition to those already mentioned is the number and character of the plates and drawings. The first is a full page plate showing nine figures of Mars in color, representing the planet as seen between Jan. 9, and March 27, 1897. The drawings were made by Mr. Lowell and the reproductions are facsimiles that give a very close representation of the telescopic view in a large instrument, as we remember the appearance of the planet at that opposition. The heliotype printing of the plate is well done.

The observations and drawings of the Satellites of Jupiter by William H. Pickering together make a noble piece of astronomical work, for completeness and thoroughness in detail. On looking over this part of the volume we are reminded of the criticisms that were made upon some parts of it while it was in progress and the preliminary results only had been given to the scientific Journals. From the full representations given and the detailed observations that accompany them, it does not seem possible that Professor Pickering could have been mistaken in what he saw, or, even wrong in the general interpretations and conclusions which he drew from those observations.

If the observations had been irregular, less systematic and less extended, as must be said of other observers fairly when put in comparison with this series, then some of the objections offered might have more probability.

The lithographic work representing the markings of the four satellites of Jupiter is presented in many full-page plates, on which are given from a few to fifty drawings of each satellite by itself with the hour in Greenwich time and the position of the central meridian. The ellipticity of these satellites as well as their surface markings are objects of very great interest. It is especially surprising that the ellipticity of the different satellites should vary so much, and we do not see how the figures of the satellites

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