i8 



NATURE 



\May 4, 1876 



remains unchanged ; thus, what is gained in remanent mag- 

 netism is lost in temporary.— Dr. Dibbit observes that ammo- 

 nium-sulphate, ammonium-oxalate, and ammonium-acetate, in 

 boiling solution, are partly decompose'!, on addition of equiva- 

 lent quantities of the chloride or the nitrate of potassium, 

 sodium, or barium ; that decomposition is greater, the greater 

 the quantity of chloride or nitrate added ; and that in all cases 

 the solution contains, at ioo°, four salts. From other experi. 

 ments he infers that the presence of salts in ammonia solu« 

 tion increases the quantity of evaporated ammonia in re- 

 lation to the evaporated vi^ater (even where the salts are 

 such as enter into known combinations with ammonia), and 

 this both at the ordinary and at the boiling temperature. — M. 

 Holtz calls attention to the polar electric attraction of fine par- 

 ticles suspended in liquids when under the influence of electric 

 currents. There is always, along with the movements of trans- 

 lations, an attachment to one pole or the other ; very well seen 

 with lycopodium powder in sulphuric ether. .Some substances 

 seem indifferent, neither wandering nor clinging to the poles, but 

 if the bottom of the vessel be clean and free Irom air moisture, 

 they form into beautiful, regular, characteristic figures. These 

 may be had, e.g., with finely-powdered manganese, or iron 

 oxide, or sawdust, in petroleum, oil of turpentine, benzine, or 

 sulphuric ether. The figures are rarely long stable ; they show 

 various internal movements, not essentially altering the character 

 of the figure; and there is sometimes rotation. — M. Sohncke 

 advances a new theory of crystalline structure, based on un« 

 limited regular point systems ; and Dr. Exner gives an account 

 of his recent researches on galvanic expansion of metallic wires ; 

 which are noticed elsewhere in our columns. 



Zeitschrift der Oesterreichinchen Gesellschaft fiir Meteorolo^e, 

 Jan. 15. —Dr. Mohn contributes an article to this number on the 

 causes of the greater depressions of the barometer in winter than 

 in summer. His present views on this subject are dit erent 

 from those given in his work on meteorology. He explains 

 that in order that a barometric minimum may attain a great 

 depth, the ascending current must develop itself with ease and 

 rapidity. Therefore, besides high temperature and a large 

 amount of vapour, the air supplying the ascending current must 

 possess qualities unlike those of the surrounding atmospheric 

 region, so that the ascended air may flow off easily at great 

 heights. The easier barometric maxima can be formed, the easier 

 the development of minima. In winter the strong continuous 

 radiation over the Continent tends to create maxima ; the cool- 

 ing of the air over the sea is moderated by the quantity of 

 vapour always present and by the ocean temperature, so that 

 minima are formed. In summer opposite conditions prevail, but 

 no nightly radiation comparable to that of the land in winter can 

 occur, and thus only small depressions are observed. In a 

 similar way the low pressure of the antarctic zone between lat. 

 70° and lat. 75° may be understood to be caused by the position 

 of this region between two districts with high pressure, the one 

 northwards about the tropic of Capricorn, the other the great 

 Frozen Antarctic Continent. Between these two maxima lies 

 an unbroken sea developing conditions favourable to the exist- 

 ence of minima. — The next paper is by Dr. G. Hellmann, on the 

 daily period of rainfall at Zechen. 



Journal de Physique, January. — The substances used in thermo- 

 meters are generally such as are not in the neighbourhood of 

 their change of state ; but (as M. Duclaux here shows) by using 

 liquids that are near critical periods, very sensitive instruments 

 may be had. Thus, if we mix 10 c.c. of crystallisable acetic 

 acid with 5, 10, 15 c.c. of benzine at about 20° we have, in each 

 case, a homogeneous mixture ; and in cooling the three liquids 

 we come, with each, to a point at which it is troubled, and at 

 length divides into two layers. The upper layer is found nearly 

 always to contain one-third of acetic acid for two-thirds of 

 benzine ; while the lower contains two-thirds of acetic acid and 

 one-third of benzine. There are few combinations of two liquids 

 that show small variations so distinctly as this one (acetic acid 

 and petroleum is another). But a good mixture miay be had by 

 taking 10 c.c. of amy lie alcohol, 25 c.c. of alcohol at 50"", and 

 adding enough water to produce a slight opalescence. The least 

 fall of temperature divides the mixture into two layers of nearly 

 equal volume. Such a mixture will serve to show, e.g., the cold 

 produced by solution of marine salt in water. By varying the 

 quantity of water the mixture may be so made as to become 

 troubled at any temperature desired ; and so a series of minimum 

 thermometers may be constructed. A little carmine may be 

 used to make the changes more apparent. — M. Deprez, in this 



number, gives some useful directions on the construction of 

 electro-magnetic registers ; and M. Branly describes the electro* 

 meter he uses for measuring electromotive force, resistance, and 

 polarisation. 



SOCIETIES AND ACADEMIES 

 London 



Chemical Society, April 28. — Prof. Andrews, F!R.S., 

 delivered a most interesting lecture on certain methods of 

 chemical research (see p. 12). 



Anthropological Institute, April 25.— Col. A. Lane- 

 Fox, president, in the chair. — Dr. Comrie, R.N., exhibited his 

 collection of weapons and articles of domestic use from New 

 Guinea, and added several particulars to his previous remarks. — 

 Mr. A. Tylor, F.G.S., read a paper on the origin of numerals. 

 He held that inventive thought had always an object origin, and 

 mentioned measures of length, as pace, foot, hand, &c., as 

 having such a source. Also in the Ptolemaic hieroglyphics, a 

 minute or second was shown by an eye-winking, answering to 

 " the twinkling of an eye." Illustrations of the Abacus and 

 mode of calculating by it were exhibited, and shown to be in 

 principle the origin of the modern calculating machine. The 

 dream of a universal language has been realised, as far as 

 numerals and arithmetical figures are concerned, and this is due 

 to their origin. — A paper by Mr. A. L. Lewis was read on 

 some apparent coincidences of custom and belief in Chaldsea 

 and other countries. He alluded, amongst other points, to the 

 marks of finger-nails upon the terra- cotta deeds that had been 

 discovered at Nineveh. They appeared to him to answer to the 

 practice of touching the seals of legal documents with the finger. 

 As regards the belief of the Assyrians in immortality, souls were 

 either united with the sun, or descended to " Bit-Edie." Annwn, 

 the country of the dead, in like manner amongst the Kymry 

 was situated in the lower regions, at the going down of the sun 

 in the west. The children of Anu, or the Sky, in Assyria, may 

 be compared with " Cum Annwn," spirits, believed in by the 

 Kymry. Amongst the Assyrian gods, Hed answered to the 

 Lycian deity "Hu." Civilisation appeared to originate with 

 the Turanians, the Semitic race merely succeeding to it. — The 

 President, Mr. A. Smee, Mr. Distant, and others, took part in 

 the discussion. 



Physical Society, April 29. — Prof. Gladstone, vice-presi- 

 dent, in the chair. — The following gentlemen were elected 

 members of the Society : Prof. F. Fuller and Capt. E. H. 

 White. — The Secretary read a communication from Sir John 

 Conroy, Bart., on a simple form of heliostat. The defect of 

 Fahrenheit's heliostat, in which the beam of sunlight is deflected 

 by a mirror moved by clock-work in a direction parallel to the 

 axis of the earth, and then in the required direction by a fixed 

 mirror, consists in the great loss of light. The author substitutes 

 two silvered mirrors for the looking-glasses usually employed, 

 and he has shown that the loss of light with this arrangement is 

 less than when the light is once reflected from a looking-glass. — 

 Mr. S. P. Thompson then made a second communication on the 

 so-called "Etheric Force," and described some experiments 

 which he has recently made in the Physical Laboratory at South 

 Kensington on the subject. The name was given by Mr. Edison, 

 the inventor of the motograph, to the sparks obtained when a 

 conductor is presented to the core of an electro-magnet, the coils 

 of which are traversed by an intermittent current. The results 

 of the experiments conducted as originally described not proving 

 satisfactory, various other arrangements were tried, and it was 

 found that if the secondary current from an induction coil be 

 used, instead of a current direct from the battery, the effects 

 are much more marked. When the induced spark was 

 diverted either wholly or partially into a short coil which was 

 insulated very perfectly from the core inside, a spark about half 

 an inch in length, which had a decided effect on the nerves 

 could be drawn off from the core, and this was sufficient to illu- 

 minate a smaU vacuum tube ; the spark, however, does not ex- 

 hibit the usual signs of polarity. It was shown by observing 

 the illumination thus produced with a rotating mirror, that the 

 discharge is in reality a reciprocating one, each spark returning 

 on its path after a minute interval of time. Under certain con- 

 ditions it is also possible to charge an electroscope either posi- 

 tively or negatively by means of the spark, and Mr. Thompson 

 has shown that the spark ignites a jet of gas but fails to deflagrate 

 metallic wire or ignite gunpowder. From the above, and other 



