256 



♦ KNOWLEDGE ♦ 



[June 1, 1886. 



through where the star images were, to a zinc plate, whose 

 surfece they cut into after their characteristic manner. 

 * * * 

 Thus was an engraving formed by the action of the stars 

 and our sun alone — or, remembering that our sun is himself 

 a star, we may say that the zincographic plate from which the 

 chart was printed, was the work of the stars only ! No 

 human hand has touched the disc-shaped hollows by which 

 eacli individual star has recorded its place. 



PHOTOGRAPHIC STUDY OF STELLAR 

 SPECTRA. 



HENRY DRAPER MEMORIAL. 



HE study of stellar spectra by means of 

 ]ibotograpliy was one of the most important 

 investigations undertaken by the late Prof. 

 Henry Draper. He was actively engaged 

 in this research during the last years of his 

 life. His plans included an extensive in- 

 vestigation, one object of which was to 

 catalogue and classify the stars by their spectra. Mrs. 

 Henry Draper has made provision, at the observatory of 

 Harvard College, for continuing these researches as a 

 memorial to her husband. The I'esults already obtained, 

 with the aid of an appropriation from the Bache Fund, 

 permit the form of the new investigation to be de6nitely 

 stated. The jiart of the sky to be surveyed is that extend- 

 ing from the North Pole to the parallel of 30 degrees south 

 declination. Each photograph will be exposed for about one 

 hour, and will include a region 1(1 degrees square. The 

 telescope employed has an aperture of 20 centimetres 

 (8 inches), and a focal length of 117 centimetres (44 inches). 

 The object-glass is covered by a prism, and tlie resulting 

 spectrum of each star in the region photographed has a 

 length of about 1 centimetre, which enables the character 

 of the spectra of stars from the fifth to the eighth magnitude 

 to be determined. A modification of the apparatus is 

 employed for the brighter stars. 



Meanwhile experiments are in progress with the 15-inch 

 equatorial, with the object of representing the spectra of 

 some typical stars upon a large scale. The spectra so far 

 obtained are about G centimetres in length, and exhibit 

 much well-defined detail. Additional experiments will be 

 tried with a spectroscope provided with a slit, as well as 

 with the simple prism hitherto employed, in order to secuie 

 the best possible definition. The present results encourage 

 the expectation that the movements of stars in the line of 

 sight may be lietter determined by the photographic method 

 than by direct observations. 



To keep the astronomical public informed of the progress 

 made in this work, specimens of the photographs obtained 

 will be gratuitously distributed from time to time. The 

 first of these distributions will probably be made in a few 

 weeks. Owing to the expense of providing a large number 

 of copies, it is desirable to limit the distribution, so tav as 

 possible, to those who are interested in this class of work. 

 It is also desired, however, to send the specimens to all who 

 will find them of value from the .scientific point of view. A 

 blank form of request is attached to the present circular, 

 and may be filled out and sent to the Harvard College 

 Observatory by any one desirous of receiving the specimens, 

 but requests to the same eflfect in any form which may be 

 convenient will also be cheerfully complied with so far as 

 may prove practicable. 



EDWARD C. PICKERING, 



Director of Hiirrard College Obserratori/. 

 Cambridge, U.S., March 20, 1886. 



Theoloot as Science. — I conceive that the origin, the 

 growth, the decline, and the fall of those speculations 

 respecting the existence, the powers, and the dispositions of 

 beings analogous to men, but more or less devoid of cor- 

 poreal qualities, which may be broadly included under the 

 head of theology, are phenomena the study of which legi- 

 timately falls within the province of the anthropologist. 

 With theology as a code of dogmas which are to be believed, 

 or at any rate repeated, under penalty of present or future 

 punishment, or as a storehouse of aneesthetics for those who 

 find the pains of life too hard to bear, I have nothing to do ; 

 and, so far as it may be possible, I shall avoid the expression 

 of any opinion as to the objective truth or falsehood of the 

 systems of theological speculation of which I may find 

 occasion to speak. From my present point of view, theology 

 is regarded as a natural product of the operations of the 

 human mind, under the conditions of its existence, just as 

 any other branch of science, or the arts of architecture, or 

 music, or painting are such products. Like them, theology 

 has a history. Like them also, it is to be met with in 

 certain simple and rudimentary forms ; and these can be 

 connected by a multitude of gradations, which exist or have 

 existed among people of various ages and races, with the 

 most highly developed theologies of past and present times. 

 It is not my object to interfere, even in the slightest degree, 

 with beliefs which anybody holds sacred ; or to alter the 

 conviction of any one who is of opinion that, in dealing 

 with theology, we ought to be guided by considerations 

 different from those which would be thought appropriate if 

 the problem lay in the province of chemistry or of mine- 

 ralogy. And if people of these ways of thinking choose to 

 read beyond the present paragraph, the responsibility for 

 meeting with anything they may dislike rests with them 

 and not with me. — Professor Huxley in the " Nineteenth 

 Centnry." 



Jewish Theology. — We are all likely to be more familiar 

 with the theological history of the Israelites than with that 

 of any other nation. We may therefore fitly make it the 

 first object of our studies ; and it will be convenient to com- 

 mence with that period which lies between the invasion of 

 Canaan and the early days of the monai-chy, and answers to 

 the eleventh and twelfth centuries B.C. or thereabouts. The 

 evidence on which any conclusion as to the nature of 

 Israelitic theology in those days must be based is wholly 

 contained in the Hebrew Scriptures — an agglomeration of 

 documents which certainly belong to very diflferent ages, 

 but of the exact dates and authorship of any one of which 

 (except perhaps one or two of the prophetical writings) 

 thei'e is no evidence, either internal or external, so far as I 

 can discover, of such a nature as to justify more than a con- 

 fession of ignorance or, at most, an approximate conclusion. 

 In this venerable record of ancient life, miscalled a book, 

 when it is really a library comparable to a selection of works 

 fi'om English literature between the times of Beda and those 

 of Milton, we have the stratified deposits (often confused 

 and even with their natural order inverted) left by the 

 stream of the intellectual and moral life of Israel during 

 many centuries. Imbedded in these strata, there are nume- 

 rous remains of forms of thought which once Hved, and 

 which, though often unfortunately mere fragments, are of 

 priceless value to the anthropologist. Our task is to rescue 

 these from their relatively unimportant surroundings, and 

 by careful compai'ison with existing forms of theology to 

 make the dead world which they record live again. In 

 other words, our problem is palieontological, and the method 

 pursued must be the same as that employed in dealing with 

 other fossil remains. — Professor Huxley in the " Nineteenth 

 Century." 



