570 



NATURE 



[June 22, i<ji i 



of investigation have been the effects of the addition of free 

 acids and foreign salts on the absorption spectra. A notabU' 

 result is the discovery of well-defined " solvent bands " for 

 various substances, for example, water, alcohols, acetone, 

 glycerol, which do not show any appreciable absorption of 

 visible light. 



In general it is shown that the anions of the various 

 coloured salts play a much less important r6\c in modifying 

 the spectra than the solvent. Different salts of the same 

 anion in the same solvent usually have the same absorption 

 spectra. As, however, the absorption spectra of the powdered 

 salts mav be very different, it is evident that the solvent 

 has an iinp^ortant part in the mechanism of absorption. 



On the other hand, the absorption spectra of the same 

 salt in different solvents are often very different ; Jones and 

 Anderson have ascribed this to the formation of solvates, 

 more or less stable compounds of the salt and solvent. The 

 persistence of solvent bands varies quite widely for the 

 different solvents, appearing to be greatest for water and 

 less for the alcohols. 



Some of the uranous salts in the various solvents, water, 

 alcohols, acetone, and glycerol, show characteristic bands 

 very strongly. An attempt is being made to correlate many 

 of these well-defined phenomena with the results of the 

 Zeeman effect on similar variations of the salts and solu- 

 tions, and it is considered that the results of such investiga- 

 tions may lead to a much clearer knowledge of the 

 chemistry of compounds. In some cases it is possible to 

 break up the absorption bands into very fine bands by 

 chemical methods, as has been done with uranyl and 

 uranous salts in acetone solutions, the most marked 

 example being the action of hydrochloric acid on an acetone 

 solution of uranous chloride. 



A very noticeable result is the action of free acids on the 

 corresponding uranyl salt, e.g. acetic acid on the acetate, 

 nitric acid on the nitrate, &c. In most of these cases the 

 presence of these foreign reagents causes the uranyl bands 

 to become more intense, and, in most cases, narrower. 

 The action of all except nitric acid is to cause the uranyl 

 bands to be shifted towards the red. Nitric acid, on the 

 contrary, produces large shifts towards the violet. A very 

 important result of this analysis is that the absorption 

 bands gradually shift as one salt of a metal is transformed 

 into another by the addition of free acid. This is inter- 

 preted to mean that a series of intermediate products are 

 formed, each with its characteristic absorption spectrum, 

 although the chemical methods at present at our disposal 

 do not enable us to isolate them. 



It is also shown that rise in temperature causes the 

 general absorption of any salt in water to increase, and the 

 bands to broaden and become more intense. 



The authors summarise the discussion as to the bearing 

 of this work on the solvate theory of solution. 



An excellent series of ninety-eight photographic reproduc- 

 tions of the spectra is included in the volume. 



C. P. B. 



THE ROYAL SOCIETY CONVERSAZIONE. 



"T* HE ladies' conversazione of the Royal Society was held 

 ■*■ at the rooms of the society in Burlington House on 

 Wednesday, June 14. Many objects and experiments of 

 scientific interest were on view, but most of them were 

 described in our account of exhibits at the previous con- 

 versazione on May 10 (Nature, May 18, p. 394). It is 

 unnecessary, therefore, to refer to these again. Among 

 other exhibits at last week's function were those described 

 in the subjoined summary of the official catalogue. 



The Director, Khedivial Observatory, Helwan, Egypt. — 

 Photographs of Halley's comet, taken with the 30-inch 

 Reynolds reflector by Mr. H. Knox Shaw. The photo- 

 graphs exhibited cover the period from April 16, 1910, to 

 June 10, 1910. Royal Astronomical Society. — Photographs 

 of the planet Mars, taken by Prof. E. E. Barnard with 

 the 40-inch telescope of the Yerkes Observatory. The 

 photographs of September 24, 1909, show the region of the 

 Fastigium Aryn and Margaritifer Sinus, and those of 

 September 28 the region of the Syrtis Major. 



The Director, Royal Botanic Gardens, Kew. — (1) Collec- 

 tion of Euphorbias, showing mimetic resemblance. The 

 following species of Euphorbia, selected from the collec- 



NO. 2173, VOL. 861 



tions at the Royal Botanic Gardens, Kew, show remark- 

 able resemblance in habit to plants of other natural orders a; 

 to which they are in no way related botanically. The" 

 species of Euphorbia, together with the plants th'v 

 resemble, were exhibited side by side. 



(i) Euphorbia Berthelott 



(2) 

 (3) 

 (4) 

 (5) 

 (6) 

 (7) 

 (8) 

 (9), 

 10, 



(" 

 (12) 



colletioides 



dendroides 



hystrix 



Intisy 



polygona 



Schimperiana 



Sipolisii 



stapelioides 



sp. 



Tirucalli 



xylophylloides 



Cotyledon lincolare. 

 Khipsalis micrantha. 

 Willow twigs. 

 Cereus insularis, 

 Prunus twigs. 

 Cereus polygonus. 

 Ceropegia fusca. 

 litis quadrangularis. 

 Stapelia .micrantha. 

 Pelargonium sp. 

 Senecio junceus. 

 Epiphyllum truncatum. 



(2) Ficus Krishnae. F. Krishnae, a remarkable species j 

 most nearly allied to F. bengalensis, in which the leaves : 

 are cup-shaped, the inside of the cup being formed by the 

 under surface of the leaf. Mr. W. Favjcett. — A parasitic 

 flowering plant from Jamaica {^Scybalium jamaicense, 

 Schott and Endl.). This species is one of the Balano- 

 phoraceae, a family of parasitic flowering plants growing 

 on the roots of trees in tropical forests. They do not 

 develop chlorophyll, and are therefore altogether dependent 

 upon their host for sustenance. The seed contains an 

 embrj'o of the simplest structure, having neither coty- 

 ledons nor radicle ; it germinates in the soil, the embryo 

 grows in length, thread-like, until it touches the root of a 

 tree, and then penetrates it. When established on the root 

 it forms a tuberous rhizome, from which flowering stems 

 are produced. The flowers are very small, numerous, in 

 heads on a stalk covered with scales — male and femal'- 

 flowers on distinct heads. This species is found in 

 Jamaica, Cuba, and Hispaniola. Other species occur in 

 Brazil and Colombia. Mr. P. S. U. Pickering. F.R.S.— 

 Germination of seeds in heated soil. When soil is heat-d 

 there is formed in it a substance toxic towards the germina- 

 tion of seeds and the growth of plants. Seeds germinal- 

 more slowlv and in smaller proportions the higher th- 

 temperature' of heating up to 250°. By exposure to air 

 and moisture the toxic substance is destroyed. Plant> 

 grown rapidly in previously heated soil also show th- 

 presence of a .toxic substance, but after this has becom- 

 decomposed, such soil, owing to increased soluble contents 

 and altered bacterial conditions, promotes plant growth. 



Dr. G. H. Rodman. — A series of stereoscopic trans- 

 parencies illustrating the life-history and minute structur • 

 of the stick insect (Bacillus rossi). Stick insects ar- 

 natives of warm climates (India, Australia, the Malav 

 Peninsula), but with care they may be reared in th:- 

 country. They resemble, as their name suggests, portior- 

 of stick, and they afford an excellent example of mimicr\ . 

 The various stages during the escape of the insects from 

 their eggs are shown. The feet are provided with a pair 

 of sharp hoi>ks, by which they can cling to rough surface>. 

 and also with a pad or sucker, which enables them to get 

 a foothold on perfectly smooth surfaces. The eye is a 

 compound one, and faceted. They stand prominently out 

 from the surface of the head, and are covered at will by 

 the insect extending his forelegs directly forward in^ th-- 

 long axis of his b^y. The skin is cast several tim- - 

 during the growth of the insect. It is shown that the 

 antennae and surface of the eyes share in the desquamation 

 of the insect. Dr. Francis Ward. — (i) Photographs of fish 

 life, as seen from below the surface of the water. 

 (2) Photomicrographs of the growth of larval fish (plaice"! 

 taken from life. The photographs are taken in a pond 

 specially constructed for the purpose. In one wall of the 

 pond is a large open space which communicates with an 

 observation chamber, and between this chamber and the 

 water in the pond is a sheet of plate glass. Concealed in 

 the chamber, the observer can watch the fish as they appear 

 to each other in the water. In consequence of the dark- 

 ness in the chamber and the light in the pond, the glass 

 acts as a mirror, and the fish merely sees himself and his 

 surroundings reflected, while the observer can plainly see 

 into the pond. It is thus possible to observe a timid fish 

 without disturbing him. In addition, an instantaneous 



