Sept. 15, 1 881] 



NATURE 



469 



tiou of the spectrum of magnesium were equally illusoiy, and gave 

 no proof of the decomp sition tf elementary substances. Finally 

 he discus: ed Mr. Lockyer's theory of "basic lines," and addressed 

 himself to a refutation of the same. The results recorded, he 

 said, strongly confirmed Young's observations, and left little 

 doubt that the few as yet unresolved coii cidences either would 

 yield to a higher dispersion, or were merely accidental. It would 

 mdeed be strange if amongst all the variety of chemical elements 

 and the still greater variety of vibratitins which some of them 

 weri capable of taking up, there h ere no two w hich cju'.d take 

 up vibrations of the s me period. They certainly should have 

 supposed that . ubstances like iron and titanium, w ith such a 

 large number of lines, must each consist of more than one kind 

 of molecule, and that not single lines, but several lines of each, 

 would be found repeated with the spectra of some other chemical 

 elements. The fact ihat hardly a single coincidence could be 

 established was a strong argument that the materials of iron and 

 titanium, even if they be not homogeneou-, were still dilTerent 

 from those of other chemical element-. The supposition that the 

 different elements miglit be re-olved into simple constituents and 

 even into a single substance had I'ng been a favourite specu- 

 lation with chemists; but however probable that hypothesis 

 might appear a priori, it must be acknowledged, according to 

 Prof. Dewar, that the facts derived from the most powerful 

 method of analytical investigation yet devised, gave it but scant 

 support. 



On Manganese NoduUs and their Oaurrence vn the Sea- 

 Bottom, by J. Y. Buchanan. — The author exhibited specimens 

 of the nodules obtained from the South Pacific, and also from 

 Loch Fyne ; an account of ihose obtained in Loch P'yne was 

 given in Nature, vol, xviii. p. 628. Some nodules containing 

 cobalt were also exhibited ; these the author had obtained from 

 New Caledonia. An account is given of the author's method of 

 dredging for mud. The nodules have been found to contain 

 iron oxides, copper, cobalt, nickel, sand, &c. Further, in no 

 case was the amount of oxygen found to be sufficient to form a 

 peroxide with the manganese. The kernels of these nodules are 

 usually richer in manganese oxides than the external portions. 

 Concemirg their mode of foimation the author thinks that this 

 takes place in situ, and that the nodules are not brought from a 

 distance. Further, it would appear that living organisms assist 

 in this formation, although indirectly, insomuch as the decom- 

 posing animal malter reduces the sulphates of the sea-water to 

 sulphides, which in their turn react on the iron and manganese 

 minerals (chiefly silicates) in the mud, and thus forming sulphides 

 of these metals. When the organic matter is exhausted these 

 sulphides are oxidised to oxides by the oxygen of the water, 

 forming concretions or incrustations of the ochreous oxides, 

 which naturally inclose the other and unaltered constituents of 

 the mud. 



On the Acticn of Zinc, Magr.es'um, and Iron on Acidified 

 Solutions of Ferric Sulphate, by Prof. T. E. Thorpe, Ph.D., 

 F.R.S. — The extent of the reduction of the ferric salt may vary 

 with the strength of the :olution, with its temperature, with the 

 amount of free acid pre.=ent, and lastly with the specific nature 

 of the metal employed. The author has studied the conditions 

 under which the hydrogen does work as a reducing agent. 

 Experiments were made on dilute solutions of ferric sul)>hate, 

 containing known quantities of free acid. The author finds (i) 

 that the extent of reduction, produced by a given w eight of zinc 

 in dissolving, increases with the temperature ; (2) that it is also 

 affected, altln ugh to a less degree, by the initial surface of the 

 metal exposed. Whilst the extent of reduction, as also the 

 rapidity of solution, increase with the temperatm-e, at a given 

 temperature the extent of reduction increases, although at a 

 gradually dimini.-hing rate, w ith the time of solution. The 

 rapidity of solution and extent of reduction produced by a given 

 quantity of zinc, of a given area and in a solution of a given 

 temperature, and containing a definite weight of free acid, 

 increase with the amount of reducible iron present. Experi- 

 ments made by placing zinc in contact w ith platinum showed 

 that, although the time of solution of zinc in contact with 

 platinum is considerably dimini-hed, as compai'ed with that of 

 zinc alone, little difference in the reducing effect is observed. 

 Similar results were oljtained with magnesium, although the 

 amount of reduction is from one-fourth to one-third of that 

 produced by zinc under similar conditions. The diminution of 

 the rate of solution with decrease in the amount of free acid 

 present, is far greater in the case of magnesium than in that of 

 zinc. The author concludes that his experiments strongly sup- 



port the view that the reducing power of nascent hydrogen i- 

 connected with the existence of this body in the atomic condi- 

 tion, since all conditions tending to prolong the duration of tliis 

 atomic condition augment the reducing power. 



On the Reducing Action of Zinc and A/agnesium on Vanadintn 

 Solutions, by Prof. Roscoe, LL.D., F.R.S. — From his original 

 experiments on this subject the author had drawn the conclusion 

 that, whilst the reduction in the case of zinc and sodium took 

 [ilace from VjOj to Y„0;, in the case of magnesium it only pro- 

 ceeded to Y'oOj. Later experiments have, however, shown that 

 each of these reducing agents acts in the same manner, but that 

 the reduction from Y'oOj to VjOj takes place very slowly when 

 magnesium is used. 



Note on a Neiu Method of Measuring Certain Chemical 

 Affinities, by A. Tribe. — The author points out that when a 

 metal is immersed in an electrolytic field, i.e., in an electrolyte 

 in the act of electrol) sis, and the electron otive force set up on 

 any part of its surface is sufficiei.t to decompose the medium, 

 then the positive ion separates out on that part of the surface 

 which has received negative electrification, and the negative ion 

 on the portion which is positively electrified. If such a plate be 

 of a rectangular form, and it be so placed that the lines offeree 

 are perpendicular to its surface, then the maximum electromotive 

 force is set up in the central part of the jlate, and at the edges i) 

 becomes so weak as to be unable to ini'iate any electro-chemical 

 action. If the steet be placed in the electrolytic field, so that 

 the lines of force are parallel w ith its sides and with two of its 

 edges, then the maximum electromotive force is at the end of the 

 plate and is the weakest at the centre, where it is unable to bring 

 about electro-chemical changes. Tliat this is the case is shown 

 by the boundaries of the deposits, which in many cases are very 

 sharply defined. From the intimate connection between electro- 

 motive f.rce aixi chemical affinity, the author supposed that if, 

 in a ser'es of trials, the chemical aftinities were altered, other 

 circumstances remaining the same, the magnitude of the inter- 

 medial space between the boundaries of the electro deposits 

 would increase with the force required to overcome the affinities 

 of the ions of the electrolytes. This suppo ition has been con- 

 firmed by several experiments, e.g., whh sheets or analysers of 

 silver immersed in solutions of chloride, bromide, and iodide of 

 zinc, it was f und that the intern. edial space was the greatest in 

 the case of the chloride, and in the case of the bromide it was 

 gi-eater than in the case of the iodide. 



On some fhenonu-na of the Nature of Chemico-Magnetic Action, 

 by W. Thomson, F.K.S.E.— The author bad observed that the 

 colour frcm a piece of cloth dyed with Prussian blue was dis- 

 ch.irged in the neighbourhood of a ) :ece of iron which had leen 

 lying upon it for some weeks. The ash of the portions of 

 cloth from which the colour had been di-charged was found to 

 contain but a trace of iron. Experiments were made in which 

 no in n was used, and the blue colour was bleached but slightly, 

 showing that the rcticn C( uld not be attributed to light alone. 

 Further experiments, in which -mall pieces of iron or magnets 

 were used, showed not only that the colour was dischar|Ted, but 

 that the colour so discharged appeared to be rearranged in semi- 

 circles on each side of the bar of iron. When mngnets were 

 used, the colour assumed more or less of circular forms, which 

 were developed not . nly from the poles, but from all parts of the 

 magnets. These phenomena the author does nrt regard as due 

 to magnetic action, fc-r when a piece of gutta percha tis.sue was 

 placed between the wet cloth and the magnet, no action took place, 

 even after several weeks. Similar observations have been made 

 with cloth dyed with aniline colours, and with a like result. 



On the Double Iodide of Copper and Mercury, by Prof. 

 Silvanus P. Thompson, D.Sc— After describing the prepara- 

 tion of this compound, which is cuproso-mercuric iodide, 

 Cu.Hglj, the auth. r draws attention to one property, -ni., 

 its change of colour loy a comparatively small change of tem- 

 perature. At the ordinary temper, ture this substance pos- 

 sesses a brilliant red colour, and when heateil, it bee mes black, 

 changing back to red on cooling. In thin layers this substance 

 transmits light, but becomes opaque on heating. Now according 

 to the electromngnetic theory of light, opaque bodies are the 

 best cc nductors of electricity ; therefore this double iodide of 

 copper and mercury should conduct heat better at a high than at 

 a low temperature. Experiment has -how n this to be true to a cer- 

 tain extent only, as beyond a certain temperature its conductivity 

 becomes less; this is probably due to its d-comprsition when 

 heat d beyond a given temperature. In conclusion, the author 

 pointed out several ways in which this change of colour of this 



