ratio per one hundred thousand of population. (The ratios were computed on the basis of statistics of crimes of violence compiled and published by the Record-Herald, of Chicago.) The white bars show the proportion of the population who, according to the United States census for 1900, were engaged in manufacturing pursuits, and the black bars indicate the percentage engaged in mining and quarrying: It will be observed that Pennsylvania and West Virginia are the only states in the Union which are engaged extensively in mining, and yet have a comparatively low ratio of homicides. This is largely due to the fact that the mining districts in these states are adjacent to wellpopulated and comparatively cultured communities, whereas in the West, the mines are situated in states or territories which contain few or no large cities, and wherein the rural population is of a rather low order. Colorado, for example, has but one large city, and is one of the five most sparsely settled states or territories of the (continental) Union; whereas Pennsylvania, on the other hand, has more towns of over 4,000 population than any other state, giving it the highest per cent. of urban population of any commonwealth in the Union with the exception of New York. Again, whereas West Virginia has 38.9 persons to the square mile, Nevada has 0.4. Consistently with all that has herein been stated, we find the greater percentages of foreign-born who are most given to crimes of violence in the very states shown to produce the greater proportion of homicides, and most of which are engaged most extensively in mining, as may be seen by comparing Fig. 7 with the one preceding. Not wishing needlessly to multiply examples and evidences, it may be said in conclusion that, however desirable the hundreds of thousands of ignorant immigrants annually landed on our shores may be from an economic standpoint, as much-needed laborers,' or, however charitably we may personally feel toward the hordes of hapless human beings who seek to better their condition by coming to this land of freedom and opportunities, such a vast addition of untutored and poverty-stricken people, unused to self-restraint, can not be absorbed without a material increase in crimes of violence throughout the United States, and especially in the large cities, where the recent immigration has for the greater part congested. It is to be hoped that the evidences of the Children's Court of New York City, and of police statistics in general, are symptoms rather of conditions to be remedied than of evils destined to grow more portentous. 6 The Report of Warden C. E. Haddox, of the West Virginia State Penitentiary, for 1903-04, shows that the five counties in which mining industries predominate, with a total population of 139,812, sent 419 persons; while sixteen other counties, whose population is engaged in agriculture or other equally stable pursuits, numbering in all 205,175 persons, are represented by 28 convicts. In the mining counties one person in every 333 was sent to the penitentiary; in the sixteen counties mentioned, one in each 7,327 of population was sent to prison—a difference as great as 300 is to 13. THE STUDY OF THE VARIABLE STARS BY PROFESSOR SOLON I. BAILEY, HARVARD COLLEGE OBSERVATORY THE ancient philosophers taught that the celestial bodies were in corruptible and eternal,' not subject to change, as are all terrestrial objects. In more recent times the stars were regarded merely as convenient points of reference for the determination of the motions of the planets. In this way they became known as the fixed stars. Relatively, they are indeed fixed; absolutely, all are in motion. Their light remains constant, also, for the most part, so that, if Hipparchus or Ptolemy should come back to earth after 2,000 years, he would probably notice few changes in the positions or brightness of the stars. Any one who observes the sky carefully, through a period of years, is sure to be deeply impressed with the absence of change. Nevertheless, there are many stars which undergo more or less regular changes in brightness, and such objects are known as variable stars. In some cases the whole cycle of change takes place within a few hours, while in other cases it consumes months, or even years. The amount of the variation, also, varies enormously, ranging all the way from zero to many magnitudes, how many is not known. It is possible, even probable, that at minimum the light of some variable may, for us at least, be entirely extinguished. Mr. J. A. Parkhurst found that the variable V Delphini was invisible at its minimum of 1,900 in the forty-inch refractor of the Yerkes Observatory. This, it is estimated, would make it fainter than the seventeenth magnitude. Since its light at maximum is of about the seventh magnitude, this implies a range of at least ten magnitudes. Other stars vary as much or more. A change of ten magnitudes means that at maximum its light is 10,000 times as great as that at minimum. To illustrate this we may imagine a room illuminated by 1,000 ten-candle power electric lamps, and that these are replaced by the light of a single candle. To reduce the light of our sun by ten magnitudes would be equivalent to increasing its distance 100 times, or to more than 9,000,000,000 miles. At such a distance its apparent size would be less than the present mean size of Jupiter or Venus. Fortunately our sun, if a variable star as seems probable, has a small range of variation. The general problem of variable stars may be divided into three parts the discovery of the variables, the observation of all the phenomena involved, and the search for the causes. The present genera tion, thanks to the powerful aid of photographic methods, may hope to bring near completion the first part of the problem, and to make good progress on the two remaining portions. The existence of a variable star was probably first recognized by Holwarda of Franeeker, in 1639. The number was slowly increased, and some knowledge of their nature learned during the next two centuries. Their observation was placed on a scientific basis through the labors of various astronomers, especially Argelander and Schönfeld. The latter astronomer issued, in 1865, a catalogue of 113 variables, and later, one of 165 variables, which included all stars then known to be variable. The list was enlarged, in 1883, at the Harvard Observatory by the addition of forty-eight variables. In 1888 Dr. S. C. Chandler published his first catalogue of variable stars, 225 in number, which had been discovered by some thirty different observers in various countries, by visual methods. Many of these observers have continued their investigations till the present time-the most successful in the line of discovery being Dr. T. D. Anderson, of Edinburgh, who by visual means alone has found forty new variables, a result truly remarkable.1 About the year 1889, however, began a rapid increase in the number of variables through the introduction of photographic methods. The first notable addition was made by Mrs. Fleming, through the examination of the photographic spectra of the stars, while engaged in the work of the Henry Draper Memorial, a research carried on at the Harvard Observatory under the direction of Professor E. C. Pickering. By means of an objective prism, placed in front of the lens of a photographic telescope of large aperture and short focal length, photographs 1Although the subject of variable stars is now under investigation at many observatories, there is still a wide field in this line of research for amateur astronomers. It is true the light-curves of many variables are now fairly well known, but new ones are constantly being discovered, the study of which offers an interesting field of investigation. It is necessary, in order to accomplish results of scientific value, that the observations be made, not only with enthusiasm, but with an intelligent conception of the future use to which they must be put. The observations need to include only two things, a record of the time, and the most precise determination possible of the brightness of the variable. The estimate of magnitude is usually made by referring the light of the variable to that of one or more adjacent stars, whose light is constant. For this purpose a series of adjacent comparison stars is selected, forming a sequence from bright to faint stars, and their brightness is carefully determined. It is very important that these magnitudes be reduced to the photometric scale. For identification of the stars the star charts of Father Hagen are admirable. Marked photographs are also extremely useful. The discovery of new variables offers, perhaps, a line of work even more fascinating than the investigation of the peculiarities of those already found. Brilliant work has been done in this direction by amateurs, but at the present time much more can be accomplished by photographic than by visual means. Among those who have done work of special value, in this country, may be mentioned Chandler, H. M. Parkhurst, J. A. Parkhurst, Sawyer and Yendell. Abroad, the number of amateur observers is large. were obtained which showed well the characteristics of scores of spectra on a single plate. Variable stars of long period were found to have spectra in which the hydrogen lines were bright, when the variables were near maximum. By taking advantage of this spectral peculiarity Mrs. Fleming has been able to pick up,' as a by-product of other investigations concerning stellar spectra, some 200 variables of long period. In 1895, the writer, while engaged in photographic work at the Arequipa Station of the Harvard Observatory, began an examination of photographs of the globular clusters of stars. By the use of improved devices for controlling the motion of the telescope, satisfactory photographs were obtained of the dense globular clusters. An ex THE GLOBULAR CLUSTER, CENTAURI, CONTAINING 128 VARIABLE STARS. To the naked eye this cluster appears as a single hazy star of the fourth magnitude. amination of these led to striking results. It was found that while certain clusters contained few or no variable stars, other similar clusters were closely packed with them. Messier 3, a faint group, barely visible as a hazy star to the naked eye, was found to contain 137 variables out of 900 stars examined, or about one in every seven stars. This is by far the greatest proportion of variables yet found anywhere in the sky. Over 500 variable stars have been found so far in dense globular clusters, and, undoubtedly, these do not entirely exhaust the number. Madame L. Ceraski, wife of the director of the astronomical observatory of Moscow, has found a large number of variables by an examination of photographs made by M. Blajko, of the same observa VOL. LXIX.-12. tory. Madame Ceraski has been especially successful in finding variables of the interesting Algol type. Of sixty-seven variable stars discovered by her, no less than ten are of this class. This is remarkable when we take into consideration that of over 3,000 variables now known only thirty-eight are of the Algol type. Through her generous gifts in aid of astronomical research, the late Miss Catherine W. Bruce, of New York, made her name widely known in astronomical circles. Dr. Max Wolf, director of the Astrophysical Observatory at Heidelberg, was presented by her with a photographic telescope, which has enabled him not only to find some seventy new asteroids, but also to increase materially the number of known THE SMALL MAGELLANIC CLOUD IN WHICH NEARLY A THOUSAND VARIABLE STARS variables. Dr. Wolf, recently assisted by Frau G. Wolf, has discovered about 200 new variable stars. Nowhere else, however, has so large a collection of celestial photographs been made, covering so long a period of time, as at the Harvard Observatory. In 1903, Professor Pickering instituted, among other pieces of work, an examination of the Magellanic Clouds. This work was assigned to Miss H. S. Leavitt, who has shown rare talent for this line of investigation. The regions selected were very fortunate, also, since, aside from the dense globular clusters, no other region has been found as rich in variables as the Small Cloud, although the Large Cloud also promises to yield nearly as many. It should be noted that the Magellanic Clouds are by no means merely irregular extensions of the Milky Way. They appear to be as unique in structure as in position. |