Nov. 23, 1888.] 



SCIENTIFIC NEWS. 



535 



animals much higher in the scale of creation than lizards. 

 Among various human races there are traditions of men 

 with a median eye, either in addition to the ordinary 

 pair or in their stead, as in the fabled Cyclops. All the 

 old mythologies refer to such eyes. In India the gods, 

 especially Seeva, are adorned with this feature, and to 

 this day it is painted on the foreheads of the dancing- 

 girls. The question at once arises, how have such tradi- 

 tions originated and been handed down ? Leaving man- 

 kind on one side, we have no specimen of a mammalian 

 skull with the aperture necessary for such an eye to act 

 as a light organ. Yet it is difficult to understand that 

 ancient nations can have invented the existence of such 

 an organ, and have assigned to it the place which it 

 would have to occupy. 



FLUORESCENCE AND PHOSPHORES- 

 CENCE. 



A S the terms " fluorescence " and " phosphorescence " 

 ^*- often occur in scientific and semi-scientific litera- 

 ture without any satisfactory explanation of the nature of 

 the phenomena to which they are applied, we extract 

 from Wiedemann's Annakn the substance of a memoir on 

 the subject by Dr. E. Wiedemann. This physicist points 

 out that we have to distinguish two principal forms of 

 the development of light. The normal production of 

 light ensues when the motion of the molecules of any 

 substance is so intensified by the accession of heat that 

 it occasions luminous vibrations of the atoms of the 

 ether. But in addition to this kind of production of light 

 there is another in which illumination is manifested 

 without any accompanying rise of temperature. Wiede- 

 mann proposes for this kind of the development of light 

 the general name luminescence, and calls the bodies which 

 possess this property luminescent. Luminescence in- 

 cludes fluorescence, phosphorescence, the electric 

 illumination of gases, and the light produced during 

 certain chemical processes and when certain crystals 

 are slightly heated. 



Whilst in normally luminous substances of any given 

 absorptive power the intensity of the luminous vibra- 

 tions is completely determined by their temperature, this 

 does not hold good in luminescent substances. But we may 

 for comparison speak of a temperature of luminescence 

 for rays of any given wave-length. It is namely that 

 temperature at which the body in question, if heated 

 alone without any external excitement, would send out 

 light of the same intensity as that derived from 

 luminescence. We thus obtain a standard for the 

 strength of the vibrations which produce light as com- 

 pared with the other existing molecular motions. 



As hitherto fluorescence has been observed only in 

 liquids, and phosphorescence only in solids, Dr. Wiede- 

 mann proposes a method for converting fluorescence 

 into phosphorescence by the gradual addition of colloid 

 substances. 



It appeared in his experiments that nearly all sub- 

 stances which are luminescent in solution by incident 

 light, do the same if their solutions are mixed with 

 gelatine and allowed to dry up. Whilst watery solu- 

 tions are luminous only during the incidence of light, or 

 in other words are fluorescent, the dried up gelatinous 

 solutions retain their light for a considerable time after- 

 wards, that is, they are phosphorescent. Sulphate of 

 quinine displays this property in a beautiful and pro- 

 longed rrianne'r. Gelatine to which a little glycerine has 



been added is distinctly phosphorescent after an admix- 

 ture of fluorescent substances, as it lies on the boundary 

 between liquids and solids. Experiment therefore shows 

 that a fluorescent body may be rendered phosphorescent 

 by restricting more and more the free mobility of its 

 molecules. 



An Introduction to Practical Inorganic Chemistry. By 

 William Gage, F.C.S., F.I.C. London: Longmans, 

 Green, and Co. 



If we do not surpass every neighbouring nation in the 

 quantity of original chemical research which we produce, 

 we certainly exceed all the rest of the world collectively 

 in the number of elementary treatises, handbooks, and 

 manuals which we put forth. This phenomenon is not 

 without its difficulties. It may be asked how the authors 

 persuade themselves that there is room for works which 

 cannot and do not contain anything novel in point either 

 of fact or theory ? And, again, how are publishers found 

 willing to undertake the issue of these publications ? 

 As a rule, these gentlemen are somewhat shy of 

 scientific books. We suspect the solution of the problem 

 must lie in the unhappy character which higher education 

 has assumed in England. 



In the little work before us there is nothing to which 

 exception can be taken as erroneous, but, on the other 

 hand, we do not find in it any feature which gives it a 

 marked superiority over its rivals. 



Handbook to Breeding, Diseases, Treatment, Care, and 

 Choice of Foreign Aviary Birds, including how to 

 Tame and Teach Birds to Speak, and Chapters on 

 Management, Cages, Seeds, Insect Foods, Pastes, 

 Dainties, etc. By Dr. Karl Russ. (Authorised 

 Translation.) London : Dean and Son. 

 This little work, which is not written in the most 

 idiomatic English, will prove very useful to those who 

 attempt the establishment or management of an aviary. 

 The author utters a much-needed protest against the 

 cruelties practised in the importation of live birds. 

 The way in which parrots are brought over in con- 

 fined boxes, neither cleaned nor ventilated, is truly 

 painful. Few of them die on the passage, but many 

 carry in their systems the germs of fatal disease, and 

 perish soon after they have been sold. 



Earthquakes. — A severe earthquake was felt in 

 Sikkim on the 9th inst. 



The Eclipse of the Sun in 1887. — The Physico- 

 Chemical Society of St. Petersburg has published (La 

 Nature) the observations made by Professor Mendelejeff 

 during his balloon ascent at Twer. From photographs 

 obtained on the shore of Lake Baikal, and at the Bay of 

 Possiet on the frontiers of Corea, it appears that the 

 corona is not a simple phenomenon of diffraction, but is 

 produced by objects existing around the sun. A portion 

 of the rays of the corona seems to be connected with 

 the spots and the protuberances of the sun. Dur ng the 

 eclipse the barometric pressure was reduced by 1 of a 

 millimetre, owing to condensation in the earth's atmo- 

 sphere. The thermometer fell i'6 degs. in the shade, and 

 8 p 6 degs. in the sun. The force of the wind was dimin- 

 ished. As to the alleged effects upon the magnetic needle 

 the reports are contradictory. 



