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Maitland (chairman), Sir G. Fiddes, Sir F. Lugard, Sir Hugh Clifford, Sir Owen Philipps, Mr. G. A. Moore, Mr. T. Walkden, Sir W. G. Watson, Bt., Mr. L. Couper, Prof. W. R. Dunstan, Mr. T. Middleton, Mr. T. Worthington, and Mr. T. Wiles. The secretary is Mr. J. E. W. Flood, of the Colonial Office.

THE death is announced of Dr. B. Fischer, Professor of Hygiene and Bacteriology in the University of Kiel, who recently succumbed to heart-failure near Ypres. In the early days of bacteriology he studied. the action of antiseptics and disinfectants upon bacteria, and afterwards made important contributions on the phosphorescent and chromogenic bacteria and on bacterial structure and classification. The latter formed the subject of a series of lectures, an English translation of which appeared under the title of "The Structure and Functions of the Bacteria," which has passed through two or three editions and forms an admirable introduction to the more botanical side of bacteriology.

THE death is announced of Madame Osterberg, the head of the Swedish physical training movement in England. In 1880 she was appointed superintendent of the physical training department of the London School Board. In 1885 she started at Hampstead the first college in this country for teaching Swedish drill, which in 1895 was moved to Dartford Heath. The college was enlarged several times, the curriculum becoming more scientific, and a laboratory was added some years ago for research and experiment. Some eighteen months ago Madame Osterberg desired to relinquish the active direction of the work of the college. In so doing she wished, in the national interest, to secure the continuation of the work which had been so successfully developed. With this purpose in view she offered to transfer the college to the Government. For reasons in no way connected with the college it was found impracticable to accept the offer, and Madame Osterberg was advised to create a trust. Almost her last act before her death was to sign the trust deed, vesting her property in a trust with the object of carrying on the college in the national interest on its existing lines.

WE regret to note the death of Major A. M. Downie, of the 5th Highland Light Infantry. Major Downie was wounded on July 12 during operations in the Gallipoli Peninsula, and died on July 23. He was well known in engineering circles in Glasgow; he was educated at Allan Glen's School and at Glasgow University, where he took the degree of B.Sc. in engineering. At a comparatively early age he was appointed managing director of Messrs. D. Stewart and Co., Ltd., where his attainments proved of great service in developing the specialities of the firm sugar machinery.

ACCORDING to a German wireless message, the death has just occurred, at Lichterfelde, Berlin, at the age of sixty-nine years, of Dr. Richard Kiepert, the cartographer.

WE regret to record the death of Rear-Admiral Benjamin Franklin Isherwood, who was engineer-inchief of the United States Navy during the American

Civil War. A short account of his career is given in Engineering. He was trained at the Albany Academy, and his early practical work was connected with railway construction. He was one of the first members of the Engineer Corps of the United States Navy, and saw service in the Mexican War in 1846 in the Princeton, the first screw-propelled vessel of the United States Navy. He was appointed engineer-in-chief of the navy in 1861. On his retirement he took up his residence in New York and devoted his energies to scientific research and literary work.

THE annual congress of the British Archæologic... Association will be held in the Isle of Wight from August 18-21 inclusive. On the evening of the opening day the president, Mr. C. E. Keyser, will deliver his presidential address at Ryde. On August 19 a joint meeting will be held with the Hampshire Field Club and Archæological Society, and arrangements have been made for visits to various places of interest on that day and on the concluding days of the meeting.

THE autumn meeting of the Institute of Metals will be held in the rooms of the Chemical Society on September 17. The following papers may be expected to be communicated:-The corrosion of gun-metal, Dr. C. H. Desch; metallic crystal twinning by direct mechanical strain, Prof. C. A. Edwards; notes on the copper-rich kalchoids, Profs. Brinton and S. L. Hort; the constitution of brasses containing small percentages of tin, Dr. O. F. Hudson and R. H. Jones; (a) structural changes in industrial brasses, (b) hardness of copper-zinc alloys, Dr. D. Meneghini; specifications for alloys for high-speed superheat steam turbine blading, W. B. Parker; the physical properties of metals as functions of each other, Dr. A. H. Stuart; detection of internal blow-holes in metal cast

ings by means of X-rays, C. H. Tonamy; a thermostat for moderate and high temperatures, J. L. Haughton and D. Hanson.

It is intended to celebrate the twentieth anniversary of the New York Botanical Garden in Bronx Park during the week beginning on September 6 next. In addition to meetings in the garden itself, there are to be visits to Staten Island for the study of the coastal flora, to the pine barrens of New Jersey, and to the Brooklyn Botanical Garden.

THE general programme of the ninety-seventh annual meeting of the Société Helvétique des Sciences naturelles to be held at Geneva on September 12-15 has now been issued. It will be remembered that this year is also the centenary of the foundation of the society. On September 13 the president, Prof. Amé Pictet, wi deliver the opening address, and a lecture will be given by Prof. A. Heim, of Zurich, on new light is the investigation of the Jura Mountains. On September 14 the sectional meetings will take place, and on the concluding day the following lectures have been arranged :-Prof. P. L. Mercanton, of Lausanne, o the results of forty years' measurements of the Rhone glacier; Dr. Fritz Garasin, of Bale, on an archipelago in the Pacific Ocean: the Loyalty Islands; and Dr. E. Rübel, of Zurich, on the international plant geography excursion through North America. The presi

dents of the various sections at this year's meeting are:-Mathematics and astronomy, Prof. H. Fehr; physics and geophysics, Prof. C. E. Guye; geography and mineralogy, Prof. Ch. Sarasin; chemistry, Dr. F. Reverdin; botany, Dr. J. Briquet; zoology, Dr. M. Bedot; entomology, Dr. Arnold Pictet; anthropology and ethnography, Dr. Eugène Pittard.

STUDENTS of the mythology of primitive races have hitherto mainly dealt with the problem from the point of view of folklore and philosophy. Many tabulations of the incidents out of which the legends have been built up have been made, but these have been as a rule merely mechanical. It shows the liberal definition of scientific research in the Geological Survey of Canada that it has published, as Museum Bulletin No. 16, an elaborate disquisition by Mr. Paul Radin on the literary aspects of North American mythology. When once we admit that in dealing with primitive mythology we are discussing literature in the true sense of the word, it becomes inevitable to apply to it the same methods of analysis and criticism that we apply to any modern literature, paying due regard to the personality of the author or author-raconteur, his literary and stylistic peculiarities. The author of this paper deals specially with the theories of Ehrenreich and other German writers, who argue that there must be a single original and correct version of every myth. The essay is interesting and serves to modify in some degree current views of the methods by which this body of legend was constructed.

IN Man for August, the Hon. J. Abercromby describes the few remaining examples of plastic art from the Grand Canary. There is a little difficulty about some of the specimens, as a collection from Mexico seems to have been mixed up with local articles in the Museum of Las Palmas. One specimen, perhaps the image of a goddess, seems to be of the steatopygous type, and another, showing an abnormal development of the biceps, may represent a wrestler. The steatopygous type cannot be Mexican, as this feature is believed to be absent in art from that country. As steatopygy prevailed among the Berber-speaking tribes of North Africa and the Sahara, and shows itself in some early figurines from the Ægean, it is possible that it may have extended to the Grand Canary. The examples illustrated are exceedingly rude, but they are interesting as examples of a very primitive school of art.

IN Folk-lore for June, Mr. W. J. Perry discusses Myths of Origin and the Home of the Dead in Indonesia. He arrives at the conclusion that the land of the dead, when situated on earth, is usually in the direction of the land whence the people who believe in it suppose themselves to have come. If the journey of the spirit be over water, a canoe for its use is generally provided, or in some cases the corpse may be actually conveyed to the homeland. When the home of the dead is a mountain, it implies that the tribe traces its origin to a mountain, and tree-disposal is often accompanied by a myth of origin from some kind of tree. Interment, he

suggests, implies an origin from the earth, and the use of stone sepulchres implies a myth of origin from stones. These conclusions may be supported by the evidence from Indonesia, but they will not be accepted as of general application, and a treatment of the subject from the comparative point of view is much to be desired.

IN Memoir No. 75 of the Department of Mines, Canada, Mr. F. G. Speck contributes an account of the decorative art of the Indian tribes of Connecticut. Much work has recently been done among the eastern Algonkin tribes, many specimens of their art industries have been collected, and information has been procured from several aged Indians of the Mohegan and Niantic tribes of eastern Connecticut. The artistic capacity of these people is chiefly shown in painting on baskets, while decorative wood carving on household utensils and sometimes upon implements was common, but bead-work was only of secondary importance. This monograph is therefore specially devoted to basketry, and the materials, implements, and designs are fully described. Some of this work is highly ingenious and beautiful, and the memoir may prove useful to the authorities of some of our technical schools.

PROF. W. H. THOMPSON, who occupies the chair of physiology at Trinity College, Dublin, has pub lished a little pamphlet on "Food Values," the proceeds of the sale of which will be devoted to the Dublin University Voluntary Aid Detachment Hospital. It deals primarily with the food supplies in Ireland, but may be applied, so far as its chief data are concerned, to the food supply of any nation. In these days, when economy is so urgent, its appearance is very timely. It deals in clear language which "he who runs may read" with the fundamental principles of diet. Mere weight is no criterion of the energy value of any food. The amount of water must be deducted, and many of the most expensive foods contain most water. After this the chemical constitution of the remainder (proteins, fats, carbohydrates, salts) must be considered, and, finally, the amount of each of the constituents which is digestible. The latter factor is much influenced by the method of cooking adopted. All these points are considered, and a number of useful illustrations help to elucidate the text. Emphasis is put upon the substitution of the cheaper forms of the more highly nutritious vegetable foods for those of animal origin. It is here that cooking (the weak point in many British households) is all-important. The bad or insufficient cooking of meaty foods does not profoundly affect their digestibility, although it influences their appetising quality, a by no means unimportant matter; but a badly cooked vegetable diet is not only destitute of the latter quality, but is very largely incapable of being digested. We are glad to see that a number of useful recipes are given, which enhance the practical value of this useful pamphlet.

THE economic resources of German South-West Africa form the subject of an article in the Bulletin of the Imperial Institute, vol. xiii., No. 2, just issued.

The value of the article is enhanced by a useful map showing the railways, rivers, diamondiferous areas, etc., and an account of the geology, meteorology, mineral resources, and agricultural conditions of the country is given. Diamonds were discovered in 1908, and the value of the output in 1912 was 1,520,7041. Gold, marble, and various other economic minerals of importance are found. As regards agriculture, stockraising has received considerable attention, and in the middle districts and south, where irrigation is possible, a good many crops are grown. Tobaccogrowing has been encouraged at the Government station Okahandja, and cotton of good quality has been grown experimentally. Grapes, peaches, apricots, etc., have also been successfully grown, and various dry-country trees are being grown at the forest stations.

UNDER the title of "The Wonderland of California," Mr. Herman Whitaker, in the July issue of the National Geographic Magazine, deals with some of the magnificent scenery of the peninsula. The paper is, as usual, illustrated by a splendid collection of photographs, among which those of the entrance of the Golden Gate, the magnificent trees in the State Redwood Park near Boulder Creek, the Bridal Veil waterfalls on Merced River, the views of the Yosemite Valley, and of the mighty granite peak known as El Capitan, are particularly impressive. Now that the Continent is likely to be barred for some time to come, travellers in search of the beautiful may well direct their attention to the country described in this pleasant paper.

INASMUCH as the wheat-producing capabilities of the non-belligerent nations is now a matter of the most vital importance, it is disconcerting to find that the Hessian fly, during the past season, has inflicted | immense damage to the wheat crop of the United States, millions of bushels having been ruined. What is more, unless strenuous efforts are immediately made, the devastation will assume far more alarming proportions during the coming year. To avert this, if possible, the United States Department of Agriculture has just issued a leaflet, which cannot be too widely read by British farmers, for this country is by no means immune to attacks from this insidious parasite. The farmers over the vast area now infected are exhorted to act on the advice ignored by them, in spite of repeated warnings, during 1914. It is once more pointed out that this pest can be practically exterminated by adopting the simple precaution of delaying the autumn wheat-sowing until after the adult flies emerging from the "flax-seed" or larval cases adhering to the straw of the summer wheat have perished, which they must do soon after assuming the adult stage. They will thus die without leaving offspring, since they will find no nidus for their eggs. Wherever possible, all stubbles are to burned, and where this is not possible they should be deeply ploughed in and the ground rolled. Further, rotation of crops should be adopted whenever possible. Where good seed-wheat is sown on generous ground,

a mild attack of this fly may even prove beneficial since the early developing larvæ destroy the fir shoots and cause the plant to "tiller." Maps show ing the best average dates for sowing, according t latitude, and diagrams illustrating the life-history the fly, add immensely to the value of this leaflet.

FROM the Kew Bulletin we learn that the new laboratory for the exclusive investigation of problems in plant pathology is now in use. The laboratory has been formed by the alteration of two Georgion cottages facing Kew Green, and contains several research rooms and a large library. The cottages were formerly houses in the occupation of Ladies of the Bedchamber when the Court was in residence at Kew, and the plaster ceilings in some of the rooms are of considerable beauty. Until now, much of the Board of Agriculture's pathological work has been. carried out at Kew in the Jodrell Laboratory, but owing to the increasing importance of the work, the establishment of a separate institute with its own staff of plant pathologists has become an imperative necessity. The attention of the staff will be devoted primarily to the investigation of diseases caused by fungi, both at home and in our Colonies, and special research in connection with important problems in plant pathology will also be undertaken. Mr. A. D. Cotton, assistant in the herbarium, has been promoted to a first-class assistantship in connection with the new laboratory, and Mr. W. B. Brierley, of Manchester University, has also been appointed a first-class assistant. A temporary assistant and a preparer comprise the staff up to the present. A portion of the laboratory is being used temporarily by the entomologist of the Board of Agriculture, so that opportunity is also afforded for the investigation of plant diseases caused by insects.

OWING to the high price of wheat flour, attempts are being made in the West Indies to replace part of the imported flour by locally prepared products. An analysis of a sample of banana flour from Jamaica is given in the current number of the Bulletin of the

Imperial Institute (vol. xiii., No. 2). Compared with

wheat flour or maize meal, it was found to have a lower nutritive value, owing to the much smaller percentage of proteins. The meal has rather a pronounced aroma, but as a partial substitute for wheat flour or maize meal it may prove useful locally.

IN the Indian Forest Records, vol. v., part vi.. of May, 1915, Mr. R. S. Hole describes a new species of forest grass from Burma under the name Spodiopogon lacei. The paper is illustrated by excellent photographs of the grass and drawings of the details of the structure of the spikelets and flowers, the number of the spikelets in the raceme and of flowers in each spikelet being important features in the genus. In this species the racemes consist of three to nine spikelets, and are usually two-flowered.

THE flowers of Milton form the subject of the first instalment of a paper, by the veteran Canon Ellacombe, in the Gardener's Chronicle for July 17. It will be remembered that he has already written on the flowers of Chaucer, Spenser, and Gower, and the

present paper is of equal value to its predecessors. Milton had not the knowledge of plants possessed by the other three poets, but the Canon's notes are full of interest. Milton's amaranth still remains a puzzle, but as he places it in Paradise, further earthly research seems useless.

IN the current number (vol. xiii., No. 2) of the Imperial Institute Bulletin, Prof. J. B. Harrison and Mr. C. K. Bancroft contribute a paper on "The Field and Forest Resources of British Guiana." Some 55,770,000 acres of land are estimated to be open for beneficial occupation, some 9,000,000 of which are easily accessible. Rice is a product which may be grown over large areas, and the success which has attended its culture shows that the colony might well become the granary of the West Indies in this particular grain. Forestry development is limited by difficulties of transportation, but of timber there is abundance and of good quality. Balata, which occurs all over the colony, is one of the most important forest trees, and greenheart is perhaps the best known of all the timbers of British Guiana.

Ar the monthly general meeting of the Zoological Society of London, held July 21, special attention was directed to the hatching, in the menagerie, of a white-browed wood swallow and two white storks. Since the total number of visitors to the Gardens between January 1 and June 30 shows a decrease of 120,993, it would seem that the war has, during this period, seriously crippled the Society; but matters are, happily, not so bad as this statement, in itself, would seem to show, for the receipts for admission at the gates, as compared with the corresponding period for the last ten years, show a deficiency of no more than 404l., which may well be made up during the next few months.

THE investigation of another egg of Ornithorhynchus, described in the current number of the Quarterly Journal of Microscopical Science (vol. Ixi., part i.), has afforded Profs. Wilson and Hill an opportunity of revising their views on the subject of the so-called primitive or archenteric knot. This structure was supposed to mark the position of the blastopore, but to come into relation with the primitive streak only secondarily, originally lying outside the embryonic shield. Both Keibel and Assheton criticised this interpretation, and suggested that the supposed archenteric knot in the younger stages of Ornithorhynchus might in reality be the yolk-navel. This view is definitely accepted by Profs. Wilson and Hill, who state that they feel with Assheton that "another stumbling-block has been removed from the path of the student of mammalian embryology."

THE way in which animals learn by the method of so-called trial and error has now been rendered fairly comprehensible by a considerable body of experimental work, largely conducted in the psychological laboratories of the United States. In a recent "Behavior Monograph" (No. 10) of the well-known series edited by Prof. J. B. Watson, Mr. J. L. Ulrich discusses the distribution of effort in learning in the white

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The chief questions to which he seeks an answer are these: Given three "problems" to be practically solved by behaviour which has to be learnt, what in each several case is the optimum distribution of trials; once in three days, once a day, or thrice a day? The answer seems to be that once in three days gives the minimum number of trials before the lesson is completely learnt, but that with three trials a day the lesson is learnt in a shorter period of time. It seems, too, that when three modes of behaviour are learned abreast, trials in each being made on the same day, infrequent practice, say one trial in each per diem, is advantageous, and that under these conditions a much larger number of trials is required for the solution of each of the problems than is required when the modes of behaviour are learnt one at a time. Physiological interpretation is tentatively suggested.

In a series of three papers published by the Edinburgh and East of Scotland College of Agriculture, Dr. J. P. M'Gowan discusses the epidemiology and pathology of three important animal diseases, swinefever, louping-ill of sheep, and chicken-cholera. Louping-ill he considers to be caused by the Bacillus bipolaris septicus ovium; the disease is divisible into several varieties, and a "pseudo-louping-ill" is also known. Swine-fever is generally considered to be caused by a "filter-passer," but the view is expressed that the evidence for this being the case is far from complete. Chicken-cholera is caused by the Bacillus pullorum, but there are probably several varieties of this organism, and "white diarrhoea" of poultry and "white scour" of lambs are probably caused by similar micro-organisms.

In an article on the production of X-ray bulbs in France (La Nature, July 10) it is pointed out that the statement that suitable French glass was not available at the outbreak of war was inaccurate. Since 1904 Appert Bros. have made suitable glass, and that though glass blowers preferred Thuringen glass, it was on grounds of economy only, and the Clichy factory was able to supply similar glass when the stocks became exhausted. From analyses of German glass by M. Matignon it was found possible to imitate it, and glass even more transparent to X-rays is now made. Pilon's modification of the Coolidge tube is described, showing how satisfactory cooling of the antikathode is obtained. The 1915 model gives a steady discharge even for such long periods as 1 hour 20 minutes, with perfect control of the character of discharge.

La Nature for July 10 also contains a very interesting article on the torpedo. Reference is made to the early history of the torpedo; to Whitehead's early pattern of a speed of only 6 knots, and capable of covering a distance of 600 metres. The great progress made to the present torpedo, with a speed of 45 knots and 10,000 metres range, carrying a charge of 150 kilos. of high explosive, is a notable achievement. An excellent description is given of the manner in which the difficulties of control of immersion and direction have been overcome by means of the hydro

static balance and gyroscope. As is well known, compressed air (at 150 kilos. per square centimetre) is used for the engines. On expansion it is very materially cooled, and a reference is made to a modern arrangement for re-heating the air by injection of an alcohol or petrol spray, together with a fine spray of watera method which leads to a great increase in speed and run of the torpedo. The article deals further with the interesting experimental station of the Schneider firm -the Batterie des Maures-situated in the roads of Hyères.

In a recent article (NATURE, August 5) on modern methods for the preparation of hydrogen for balloons and dirigibles, the difficulties attendant on the use and transport of acid for the well-known methods of generation from zinc or iron were mentioned. One of the greatest troubles arising from the use of gas prepared by these reactions has been due to impurities in the gas. An article in La Nature (July 10) deals specially with this method of preparation and the purification of the gas. Among the impurities are hydrogen arsenide, antimonide, and selenide, all poisonous gases, and which led to the death of two employees and serious illness of three others engaged at the ChalaisMeudon Aerodrome in 1900. Sulphuretted hydrogen, formed by reduction in the generators, has a very deleterious action on the varnish of the fabric, which, containing lead, is attacked, forming the sulphide, and further, by the action of moist air, on the tissue itself. Exposed metal in dirigibles is also subject to its attack. Other impurities are water vapour, carbon dioxide, and gaseous hydrocarbons, which seriously diminish the lifting power of the gas. Purification entails first washing the gas to remove acid spray, passage through a special purifier containing a moist mixture of iron sulphate and lime on sawdust, and finally through soda. The iron purifying material which has absorbed the sulphuretted hydrogen is regenerated by exposure on grids to the air. The cost of purification is stated to be 15 to 2 centimes per cubic metre.

AN investigation by Messrs. G. K. Burgess and P. D. Merica, of the Bureau of Standards, a preliminary account of which appears in the Journal of the Washington Academy of Sciences for July 19, appears to provide a complete explanation of the mysterious failure of tin fusible boiler plugs. It will be remembered that these plugs are inserted in the crowns of boiler furnaces or flues and that their function is to give warning of overheating of the boiler by their melting and admitting steam to the fires. It was found that the tin of plugs which had failed had been converted in service into SnO2, which melts at 1600° C. This oxidation was finally traced to the presence of zinc in the tin to the extent of 0.3 per cent. Plugs with this amount of impurity, when heated to 190°C. for 500 hours, develop a cellular structure, the walls of the cells consisting of oxidised zinc, to which oxidised tin is added with time, and the unoxidised tin is enclosed in the cells. Even when the tin is melted the cell walls may be strong enough to withstand the boiler pressure. The authors conclude that tin of at least 99.8 per cent. purity should be used for such boiler plugs.

THE July number of the Bulletin of the America Mathematical Society (xxi., 10) contains particulars of the courses in mathematics announced for the summer semester in six of the German universities Excluding such general items as "colloquium" and "seminar," the statistics work out as follows:Berlin, 13 courses by 8 lecturers; Bonn, 7 courses 4 lecturers; Frankfurt, 7 courses, 4 lecturers; Göttingen, 13 courses, 9 lecturers; Leipzig, 9 course, 4 lecturers; Munich, 11 courses, 8 lecturers. We als note the award of the Helmholtz medal of the Berlin Academy to Prof. M. Planck, and the celebration of the seventy-fifth birthday of Prof. F. Mertens, of Vienna, on November 7, 1914, and c: the seventieth birthday of Prof. Georg Cantor, e Halle, on March 3, 1915. The lists of courses de not appear to differ to any substantial degree from those published in previous years, either in the number of courses or in the character of their sub

ject-matter. To English readers they should afford some indication of the way our enemies are main taining their higher scientific educational systems in war-time. By "lecturers" in the preceding list w mean professors in most cases, but include other members of the teaching staffs.

WE are asked by Messrs. Constable and Co., Ltd., to state that they are the English publishers of "Elementary Text-book of Economic Zoology and Entomology," by Profs. Kellogg and Doane, which was reviewed in the issue of NATURE for July 1 last.

OUR ASTRONOMICAL COLUMN. ABSOLUTE SCALES OF PHOTOGRAPHIC AND PHOTOVISUAL MAGNITUDES.-A great piece of photometric work on which the 60-in. reflector of the Mount Wison Observatory is engaged is the determination of absolute scales of photographic and photovisual magnitudes covering the whole range from brightest to faintest known stars. An account of the present position of the investigation has been communicated by F. A. Seares to the National Academy of Sciences (U.S.A.), vol. i., p. 307, 1915. The method employed involves the comparison of two series of images with a known variation of intensity between the exposures. The many practical difficulties have been successfully overcome at Mount Wilson by the use of wire gauze screens and circular diaphragms. The photographic scale for the intermediate stars (10-18 mags.) was first determined in two series of exposures, one set of eleven minutes and less, the other thirty to sixty minutes; numerous determinations were made. The average difference between the mean scales from the two series, derived from nine groups of stars between 10.6 and 16-8, is only 0-015 mag. The extension to the fainter objects was effected by plates which re ceived two different exposures with the full aperture of 60 in., the longer exposures of four to five hours, the shorter approximately half an hour. The limiting photographic magnitude thus reached was about 20 The bright stars (brighter than 10 mag.) were photographed with screens or diaphragms interposed pro ducing images comparable with those of stars be tween the tenth and fifteenth magnitude, obtained with the same exposure with unreduced aperture. The entire series of photographic magnitudes of 617 objects was reduced to the international zero point

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