of the hen's egg during the development of the chick.

INQUIRIES as to the schools in which leading men in various professions were educated have been made by The School World, and the results for men of science are abstracted in Nature. Of 250 representative men of science-mostly Fellows of the Royal Society-chosen for the present inquiry, one-fifth received their early education either in private schools or at home under tutors. The schools which claim the greatest number of old pupils in the selected list are Edinburgh High School, Edinburgh Academy and Aberdeen Grammar School. The Scotch schools are followed, as regards the number of old pupils of distinguished eminence in science, by the City of London School and King's College School. Eton, Harrow and Rugby succeed these, and are in turn followed by Liverpool College, Royal Institution School (Liverpool) and St. Paul's. The remarkable

point brought out by this comparison, says Nature, is the small part the great public schools have taken in training the leaders in science of the present day. When the men who are now in the foremost rank among philosophers were receiving their early education science was almost, if not quite, omitted from the public school curriculum, with the result that comparatively few boys from such schools have become eminent in the scientific world. The neglect of science in comparison with other subjects is shown by the fact that Eton, Harrow, Rugby, Winchester, Westminster and one or two other public schools, though comparatively poor in their scientific record, are shown to have furnished the greatest number of leading men in Parliament, the church and the law, Eton leading the way as regards numbers in each of these classes.

THE Regents of the University of the State of New York have voted that the Secretary be authorized to sell any of the University publications at half price to any university institution or to any teacher or officer of such institution, and to give such publications outright to such depositories as shall be registered as entitled to such consideration because they agree to preserve and catalogue the publications and make them

available for public use. Pamphlet editions of the reports giving administrative details and information as to the workings of the department may be given away; but scientific contributions of the museum staff and other valuable matter printed as appendices to the reports, and the bound volumes containing such matter, shall not be for free distribution, but shall be sold at a nominal price approximately covering cost of paper, presswork and binding.

UNIVERSITY AND EDUCATIONAL NEWS.

In addition to Professors Picard, Mosso and Ramón y Cajal, whom we have already announced as lecturers at the decennial celebration of Clark University, to be held July 5th to 8th, we are informed that Dr. Ludwig Boltzmann, professor of theoretical physics at the University of Vienna, and Dr. August Forel, formerly professor of psychiatry at the University of Zurich, will give short courses of lectures.

MR. B. H. DUKE has made an additional gift of $50,000 to Trinity College, at Durham, N. C. THE degree of Bachelor of Science has been given to 170 candidates by the Massachusetts Institute of Technology.

IT is reported that nine professors at St. Petersburg University have resigned as an expression of sympathy with the grievances of the students.

THE REV. William H. P. Faunce, D.D., pastor of the Fifth Avenue Baptist Church, New York, has accepted the presidency of Brown University.

DR. D. J. BIEHRINGER and Dr. Tröger have been promoted to assistant professorships of chemistry in the Institute of Technology at Braunschweig. Dr. Abegg has qualified as docent in physical chemistry in the University of Breslau; Dr. Schultze in zoology in the University at Jena; Dr. Kowalevsky in mathematics in the University of Leipzig; Dr. Feitler in physical and theoretical chemistry in the Institute of Technology at Vienna; Dr. von Oppolzer in astronomy and astrophysics in the German University at Prague, and Dr. Relstab in physics in the Institute of Technology at Braunschweig.

tory in the world. The funds for its support come from the pockets of our taxpayers, and the latter, speaking through our astronomers as their mouthpiece, should be satisfied with nothing less than that the work done by the institution shall correspond to the liberality with which they are supporting it. The fact that our country has a larger proportion of the ablest astronomers of the world than any other, not excepting even Germany, leaves us without any excuse if our national observatory fails to be completely up to the present time.

For more than fifty years we have been trying an experiment in astronomical administration which no other nation ever thought of trying and which we ourselves have never tried in any other field, that of managing a great national observatory like a naval station. One of the most important questions is whether this experiment, taking the whole fifty years together, can be called a success. This question can be answered only by a critical examination of the work of the institution, as found in its volumes of published observations and official reports. In this connection it will be wise to review the laudable efforts made from time to time to improve the administration and determine the causes of their success or failure.

When the subject is considered from this point of view it is a serious question whether any other than an adverse conclusion can be reached. It is true that excellent work has now and then been done at the observatory and that this, taken in connection with the favorable impression made by the splendor of its new buildings, prepossesses

the public, which never looks below the surface in its favor. But, as was very clearly pointed out by the National Academy of Sciences in a report in 1885, this good work has been mostly the voluntary work of individuals who happened to be attached to the institution and acted on their own initiative. The part of the administration was only to get the men together and procure them facilities for work.

It should also be remembered that even this work is not by any means a permanent feature of the institution. If we take away from the latter such work as that of Seers Cook Walker in investigating the motions of Neptune, and of Professor Asaph Hall in discovering the satellites of Mars and in investigating the motions of other satellites, what have we left? If anything but a heterogeneous collection of observations and researches, sometimes intermitted entirely and sometimes carried on with vigor, sometimes devoted to one object, sometimes to another, sometimes able and sometimes useless, generally of the most perfunctory kind, nearly always with more or less imperfect instruments and with little evidence of any concerted plan, we hope the board will find it out.

An excellent text will be found in the recent catalogue of stars by Professor Eastman, which, we are told in the preface, has occupied two-thirds of the observatory force for a period of more than thirty years. What should the committee say when it compares the unflagging zeal and persistence of the author with the imperfections of the instrument he had to use?

In the same class may come the more re

cent work of Professor George A. Hill with the prime vertical transit. There can be no question of the zeal and industry with which Mr. Hill has for five years continued a series of observations bearing on one of the most important problems in exact astronomy with which we are dealing to-day. Yet the results of his work so far as published show now and then anomalies and irregularities leading to the suspicion that there is something wrong about the instrument. The cause can be found only by critical investigation. It would certainly be very regrettable if such rare qualities as those of Mr. Hill should fail to be productive of their best results through adverse circumstances which would be speedily remedied under a proper system of administration; and we hope the Committee will either demonstrate that the suspected defects of the work are unreal, or show their cause if they exist.

THE DIFFRACTION PROCESS OF COLOR

PHOTOGRAPHY.

THE production of color by photography has been accomplished in two radically different ways up to the present time. In one, the so-called Lippman process, the waves of light form directly in the photographic film laminæ of varying thickness, depending on the wave-length or color of the light. These thin laminæ show interference colors in reflected light in the same way that the soap bubble does, and these colors approximate closely the tints of the original. The technical difficulties involved in this process are so great that really very few satisfactory pictures have ever been. made by it. The other, or three-color process, has been developed along several distinct lines; the most satisfactory results having been produced by Ives with his

stereoscopic Kromskop,' in which the reproduction is so perfect that in the case of still-life subjects it would be almost impossible to distinguish between the picture and the original seen through a slightly concave lens. The theory of the threecolor method is so well known that it will be unnecessary to devote any space to it, except to remind the reader of the two chief ways in which the synthesis of the finished picture is effected from the three negatives. We have, first, the triple lantern and the Kromscope, in which the synthesis is optical, there being a direct addition of light to light in the compound colors, yellow being produced, for example, by the addition of red and green. The second method is illustrated by the modern trichromic printing in pigments. Here we do not have an addition of light to light, and, consequently, cannot produce yellow from red and green, having to produce the green by a mixture of yellow and blue. Still a third method, that of Joly & McDonough, accomplishes an optical synthesis on the retina of the eye, the picture being a linear mosaic in red, green and blue, the individual lines being too fine to be distinguished as such.

The diffraction process, which I have briefly described in the April number of the London, Edinburgh and Dublin Philosophical Magazine, is really a variation of the three-color process, though it possesses some advantages which the other methods do not have, such as the complete elimination of colored screens and pigments" from the finished picture, and the possibility of printing one picture from another. The idea of using a diffraction grating occurred to me while endeavoring to think of some way of impressing a surface with a structure capable of sending light of a certain color to the eye, and then superposing on this a second structure capable of sending light of another color, without in any way

interfering with the light furnished by the first structure. This cannot, of course, be done with inks, since if we print green ink over red the result will not be a mixture of red light and green light, but almost perfect absence of any light whatever; in other words, instead of getting yellow, we get black. Let us consider, first, how a picture in color might be produced by diffraction. Place a diffraction grating (which is merely a glass plate with fine lines ruled. on its surface) before a lens, and allow the light of a lamp to fall upon it. There will be formed, on a sheet of paper placed in the focal plane of the lens, an image of the lamp flame, and spectra, or rainbow-colored bands, on each side of it. Now, make a small hole in the sheet of paper in the red part of one of these spectra. This hole is receiving red light from the whole surface of the grating; consequently, if we get behind the paper and look through the hole we shall see the grating illuminated in pure red light over its whole extent. This is indicated in Fig. 1, where we have the red

end of the spectrum falling on the hole, the paths of the red rays from the grating to the eye being indicated by dotted lines. Now, the position of the spectra, with reference to the central image of the flame, depends on the number of lines to the inch with which the grating is ruled. The finer the ruling the farther removed from the central image are the colored bands removed. Suppose, now, we remove the grating in Fig. 1, and substitute for it one with closer ruling. The spectrum will be a The spectrum will be a

BLUE GREEN RED

IMAGE OF FLAME

SPECTRUM

light to the eye and appears green; the under strip, with the coarser ruling, sends red light to the eye and appears red; while the middle portion, where we have both rulings, sends both red and green light to the eye, and in consequence appears yellow, since the simultaneous action of red and green light on any portion of the retina causes the sensation of yellow. In other words, we have, in superposed diffraction gratings, a structure capable of sending several colors at once to the eye.

If we add the third grating we shall see the portion where all three overlap illuminated in white, produced by the mixture of red, green and blue light.

Three gratings, with 2,000 lines, 2,400 lines and 2,750 lines to the inch, will send red, green and blue light in the same di