January 12, 1899] 



NA TURE 



261 



appear in positions much higher than their actual positions, that 

 is to say, when images of them appear considerably raised above 

 their true positions. The effects of looming are very extra- 

 ordinary, and I have some slides to show you which I have 

 prepared from examples recorded by Commander William 

 Scoresby, who went on his third voyage in his ship the Baffin 

 to the Greenland whale fishery in the spring of 1822. The first 

 of these views includes several large irregularly-shaped icebergs, 

 which must cause very unusual distributions of air density, and 

 gave rise to quite remarkable vertical and lateral refractions. 

 In the second there are images of ice which was quite out of 

 sight or quite beyond the horizon. There was extraordinary 

 vertical magnification ; small hummocks of ice were drawn out 

 into spires, sometimes of a castellated shape and sometimes 

 having the appearance of naked trees ; at other times there ap- 

 peared to be a city of ice, with public edifices, spires, cjcc. , and 

 Commander Scoresby states in his book that these efl'ects were 

 constantly changing, and were never the same for two minntes 

 together. The first of these drawings, which you saw on the 

 screen, showed a curious inverted image of a ship in the sky, 

 raised considerably above the horizon ; that ship was so distant 

 that it could not be .seen with a powerful telescope. 



During the Crimean War observers on one occasion saw the 

 whole of the British P'leet inverted at a considerable height, an 

 illustration of which appeared in The Illustrated London News 

 at the time. Some very interesting cases were recorded by Dr. 

 Yince in the Bakerian lecture of 1798, read before the Royal 

 Society, some of which are delineated in the succeeding slides. 

 He remarks upon these curious phenomena that he thinks that 

 in cases of national emergency certain people should be told oft 

 with telescopes to look out for the enemy's ships, and to search 

 the horizon to see if they could detect any ships looming. Dr. 

 Yince mentions another remarkable instance in which he saw- 

 Dover Castle from Ramsgate, at a point from which the whole 

 of the keep of the castle cannot be seen, the four turrets only 

 being visible. The most curious case of lateral refraction that I 

 have been able to discover was observed at Geneva in 181S, by 

 M. Jurine ; a barque was seen approaching on the left bank of 

 the lake, and at the .same time an image of the sails was 

 observed above the water, which, instead of following the 

 direction of the barque, separated from it and appeared 

 to approach Geneva by the right bank of the lake, the 

 image moving from east to west while the barque moved 

 from north to south. This case was brought to the notice of 

 Biot, the physicist, and he, in one of the scientific journals, gave 

 a very long explanation. He came to the conclusion, from the 

 geographical features, and climatology, and the direction in which 

 the sun's rays were passing at the time of the observation, that 

 there would be considerable lateral difference in the temperature, 

 (juite sufficient to produce this phenomenon of lateral re- 

 fraction. 



Another case of curious refraction has been noticed by many 

 people — I have seen it myself particularly on the coast of 

 Norway. Low lands, and the extremity of headlands, or points 

 forming an acute angle with the horizon of the sea, and viewed 

 from a distance beyond it, appear elevated above it, with an 

 open space between the land and sea, the effect being propor- 

 tional to the amount of evaporation taking place at the surface. 



Fata Morgana is a name given to an optical phenomenon 

 sometimes seen in the Straits of Messina between Sicily and the 

 Italian coast. Minasi says : " When the rising sun shines from 

 that point whence its incident ray forms an angle of about 45' 

 on the sea of Reggio, and the bright surface of the water is not 

 disturbed either by wind or current, the spectator being placed 

 on an eminence of the city with his back to the sun and his face 

 to the sea, on a sudden there appear in the water various multi- 

 plied objects, namely, numberless series of pilasters, arches, 

 castles, columns, towers, palaces with balconies and windows, 

 valleys of trees, plains with herds and flocks, &c. , in their 

 natural colours and proper action, passing rapidly in succession 

 along the surface so long as the above-mentioned causes exist. 

 If, in addition, the atmosphere be highly impregnated with 

 vapour and dense exhalations not previously dispersed by the 

 action of the wind and waves, or rarefied by the sun — in this 

 vapour, as in a curtain, to a height of 24 or 25 feet, and nearly 

 down to the sea, the observer sees the same objects not only 

 reflected from the sea, but likewise in the air, though less dis- 

 tinct. Lastly, if the air be hazy and slightly opaque and dewy, 

 the objects appear only at the sea surface, but with prismatic 

 colours." He endeavours to prove that they are representations 



NO. 1524, VOL. 59] 



of objects on the two coasts. He considers the sea an inclined 

 speculum, on account of the rapid current which runs through 

 the Straits, and divided into different planes by contrary eddies, 

 and he ascribes the aerial morgana to the refractive and reflective 

 power of matter suspended in the air. 



Lastly, I would mention the experiments of WoUaston upon 

 the subject of refraction and mirage. First, he says, into a 

 square phial containing a little clear syrup put an equal quan- 

 tity of water in such a way that it floats without mixing, and 

 after a little time, by mutual penetration, you see effects ; if you 

 view through the syrup a card with a written word upon it, you 

 see it, and also above it an inverted and erect image of the 

 same. That is a case in which the density diminishes upwards, 

 and the ray has its concavity presented downwards. Then, 

 above the water he placed rectified spirits of wine, when the 

 inverted and erect images were seen below, these appearances 

 continuing many hours and even days, and he carried out 

 similar experiments with water at different temperatures. Kvery- 

 body knows the experiment with a red-hot poker ; the effects of 

 mirage can be seen by looking along the surface of a red-hot 

 poker, held at a distance of about a foot from a sheet of paper, 

 when there is perceptible refraction. Again, Wollaston looked 

 along a horizontal plate of glass upon which he poured ether, 

 and a line appeared instantaneously upon the opposite wall at 

 an elevation of half a degree, this effect being due to the cold 

 cau.sed by the evaporation of the volatile liquid. Finally,, 

 Brewster showed that all the phenomena of unusual refractioiv 

 might be observed by holding a heated iron over a mass of water 

 bounded by parallel plates of glass, and then substituting a colcf 

 bod y for the hot iron. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE. 



The foundation-stone of the Gordon Memorial College air 

 Khartum was laid on Thursday last by Lord Cromer, who re- 

 marked that the College would aim at dift'using knowledge of 

 agriculture, engineering, and other practical acquirements useful 

 to all classes. 



The New South Wales Government invite applications for 

 the position of Professor of Physics in the University of Sydney, 

 from University graduates under thirty-five years of age. 

 Particulars of the conditions of appointment, duties, &c., can 

 be obtained from Sir Daniel Cooper, Bart., G.C.M.G., Acting 

 Agent-General for New South Wales, 9, Victoria Street, West- 

 minster, London, S.W. 



The necessity of encouraging .scientific investigation, and of 

 providing means for training investigators, is pointed out by 

 Prof. Cleveland Abbe in the U.S. Monthly Weather Review- 

 (September 1S9S). He remarks : — A mistaken idea has widely 

 prevailed that the investigator is a genius, born and not made. 

 The history of German science has, however, shown that 

 environment and training are as important as birth and inherit- 

 ance. The whole system of education in the German, 

 universities has for five generations been directed to the 

 development of the investigator as its highest product. Those 

 who discover important new facts, laws, or principles have been 

 rewarded with the highest places in the intellectual world of that 

 nation. Tho.se who feel that they have a desire or calling for 

 scientific research are encouraged to study for the degree of 

 doctor of philosophy, a degree that is only granted when the 

 candidate has, by actual observation, experiment, or exploration, 

 made some important contribution to human knowledge. The 

 professors under whom he studies have, in their turn, made 

 many similar contributions, and are well prepared to judge of 

 the value of his work. The German universities have, during, 

 the past seventy years, published over fifty- thousand so-called 

 " doctors' dissertations," embodying the results of the works o£ 

 fifty thousand candidates. The consequence is that to-day- 

 Germany easily leads all the world in the amount and value of 

 her contributions to human knowledge and the energy with 

 which her students pursue the study of nature. 



SCIENTIFIC SERIALS. 



Bnlletin oj the Anierican Mathematical Society, December 

 1 898. — At the October meeting of the Society seven papers 

 were communicated. .-Abstracts of the papers not to be pub- 

 lished in the Bulletin are given. — Prof. Woodward's paper, on 



