1082 NATURE DECEMBER 25, 1937

Apparent Enlargement of the Sun at the time of Rising and Setting By Dr. Vaughan Cornish JT is a matter of common observation that when ment, or any intention of subsequent measure• the sun is nearly on a level with the eye and ment, but from known view-points, so that the is in the vicinit.y of the horizon its apparent size angular magnitudes of terrestrial features were afterwards ascertained from the map. The sun seen from rising above the Bernese forty miles away, measured 0·16 inch on a 7 -inch page. As seen from the sun rising above the Wetter- horn four miles away measured only 0·9 inch on a 7 -inch page. These measurements seern at to confirm the ex• pectation that the sun would be apparently en- larged in proportion to the diminution of ter• restrialfeatures by greater distance. When, how• ever, I measured the Fig. l. mountains in the two THE RISING SUN FROM BERN drawings and corn pared is greater than when high up in the sky. It is them with the distances as measured on the map, generally assumed that this is due to the circum• I found that th.e apparent magnitude in the more stance that the features of the skyline provide a true standard of instinctive comparison which enables the eye to appreciate the angle subtended by the sun's disk. It is true that the linear magni• tude of the terrestrial features is fairly well known and that the tone and other qualities of the horizon give an instinctive im• pression of its distance. The current explanation breaks down, however, under the test of actual .·•\ measurement of the apparent ( I '· .. ,_ magnitudes. These measurements / are trustworthy only if made by / \ an indirect method which side- \ tracks the critical faculty, for as soon as thought comes into play, the spontaneous impression of magnitude is impaired. The Fig. 2. measurements in question have THE RIEING SUN FROM GRINDELWALD been made from a number of sketches which I have made during the last distant view was not reduced proportionately to forty years, all drawn originally without measure- the distance, but on the contrary was subjectively

© 1937 Nature Publishing Group DECEMBER 25, 1937 NATURE 1083 magnified. The arc of horizon comprised in the viewed from Bern forty miles away. It seems, sketch made at Grindelwald was 34° ; that from therefore, that the more the eye takes in vertically Bern, 21°. Thus the subjective enlargement of the more it takes in horizontally and the less the mountains seen from Bern was 1·6, that of imposing are both dimensions. the sun being 1·7, which for this class of observa• These indications led to an interesting result on tion is practically identical. measuring drawings which comprised the peaks of Following up this clue, I measured drawings of and Monch seen from Gurten-Kulm and the arc of the horizon included in a page of my from , distant respectively about sketch-book when drawing the long line of com• 37 and 2! miles. From the former position, the paratively low hills on the west of Bournemouth arc of the horizon in the page of the sketch-book 0 0 Bay, and the lofty mountains enclosing the was 18! ; in the latter 60! • The peaks seen valley of . I found that whereas from Kleine Scheidegg stood about 26°-27° above the impression of lateral extent received in the line of sight. These measurements explain the the former case was the greater, the arc of familiar sense of disappointment experienced on the horizon comprised in the panoramic sketch near approach to mountain peaks the great was much less, that is, the eye was sooner magnitude of which has impressed the mind when satisfied when it had to deal mainly with one viewed from a distance. As we approach the dimension. mountain the field of attention steadily expands Referring again to the small apparent size of without, however, any warning sensation in the the sun when rising above a crest-line something eye. Our field of attention varies according to like 20° above the line of sight, that is, above the circumstances and the mind transfers the change of seen from Grindelwald, it will be magnitude to the objects in the field, but in the noted that the features of the view are not strung reversed sense, an actual restriction of the field out in a narrow horizontal band as when the being accompanied by apparent enlargement of range of which the Wetterhorn is a member is the objects viewed.

Expedition to Baffin Bay, I937

expedition, led by J. M. Wordie of St. Lancaster Sound, was nowhere seen. This lack of John's College, Cambridge, has returned ice, though it gave unusual opportunities for from a three months voyage to Davis Strait and archreological work and geographical exploration, Baffin Bay. The party, ten in number, had as its had the disadvantage that no large floes were main objectives the geology and archreology of available out at sea as launching grounds for Ellesmere Land and the investigation of the upper balloon flights, and cosmic ray work was there• atmosphere by free balloons. The Norwegian fore confined to the West Greenland coast. motor-sealing vessel Isbjern, of Troms0, 172 tons, The cosmic ray experiments involved the carrying a crew of twelve, was specially chartered measurement of the intensity of the radiation at for the expedition, and sailed from Leith on June great altitudes in the polar atmosphere, and 27, returning on October l. H. Carmichael and instruments were conveyed to heights of more E. G. Dymond, who was assisted by I. M. Hunter, than 25 km. by free balloons, utilizing the methods made cosmic ray investigations with high-altitude of Prof. E. Regener of Stuttgart. Two types of balloons near the magnetic pole. Eskimo anthro• apparatus were used, one designed and constructed pology and archreology were studied by T. C. by Carmichael in the Cavendish Laboratory, Lethbridge and T. T. Paterson, assisted by R. W. Cambridge, consisting of a pressure ionization Feachem and D. Leaf; geology, petrology and chamber and electrometer with photographic physiography by Paterson, H. I. Drever and recording of the ionization, pressure and tem• A. H. Robin; and botany by Feachem. perature, and the other, by Dymond in Edinburgh The year was exceptional in that no ice was met and J . A. Ratcliffe in Cambridge, a triple-coinci• with in Melville Bay, and the ship was able to dence counting set with wireless transmission of proceed as far north as Bache Peninsula in the counts and the barometric pressure. In Ellesmere Land without ice hindrance ; the addition, the intensity of the cosmic rays at sea• Middle Pack, which usually occupies the west side level was recorded by two ionization instruments, of Baffin Bay, and is fed from Smith Sound and one lent to the expedition by Regener and Hoerlin,

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