I I 



NA TURE 



[December 4, 1902 



who has only recently returned from South Africa, is shortly 

 starting for a tour in Ceylon and India in order to investigate the 

 aetiology of leprosy. 



We have received an advance copy of the second edition of 

 Merck's Index. The bulk of the work is devoted to an alpha- 

 betical list of the multitude of substances which have been intro- 

 duced of late years for medicinal use and the majority of which 

 are not to be found in the pharmacopoeias. Under each heading, 

 the nature, chemical composition and physical properties, the 

 uses and doses of the substance are indicated. Another useful 

 list gives the composition of various test-solutions that are 

 usually referred to under authors' names and the formulae for 

 which are often difficult to discover. Other tables give the 

 nature and derivation of the organic substances of the materia 

 medica, nature and composition of minerals, indicators, ^c. 

 Altogether, the work is a most useful one, both for the practising 

 physician and for the chemist and physiologist, and should find 

 a place in every laboratory. 



A i opy of the catalogue of Aurora Borealis observed in Nor- 

 way from the earliest limes until June, 1878, has been received 

 (xxiii + 422 large quarto pages, Christiania, 1902). This com- 

 prehensive catalogue was compiled by Prof. M. Tromholt ; he 

 died in 1896, and the laborious task of revising the manuscript 

 and preparing the work for publication was undertaken by his 

 friend, Prof. J. F. Schroeter, of the Christiania Observatory. 

 The first portion of the catalogue gives, in chronological order, 

 the year, month and day on which aurora was observed, to- 

 gether with the district and place, a short description of the 

 phenomenon and the source from which the information was 

 obtained, while a second section contains special descriptions of 

 individual displays. The discussion of the results shows that, 

 as regards the whole country, a maximum in the yearly period 

 occurs about the times of the equinoxes (October and March), 

 separated by a minimum in mid-winter. For the northern part 

 of the country, north of 68 30', the yearly period resembles that 

 of the polar regions, with a maximum about the winter solstice. 

 South of latitude 65 , the periods resemble those of middle lati- 

 tudes. Prof. Schroeter has also tabulated the observations of 

 Dr. Rubenson's catalogue of Swedish aurorce, and shows that 

 the same results hold, for the yearly period, for the whole of 

 Scandinavia, and for individual districts, as obtain for Norway 

 only. 



Some tests on an interesting battery, in which the de- 

 polariser is atmospheric oxygen, are described by G. Rosset 

 in a recent issue of the Centralblatt fur Accumulatorcn- 

 Elemental. The cell consists of a zinc electrode dipping into 

 a solution of salammoniac surrounding a porous jar ; a semi- 

 permeable membiane o( ferrocyanide of copper is formed in the 

 interstices of the jar, which contains a carbon rod dipping into 

 an ammoniacal solution of cupric oxide. When the cell is dis- 

 charging, the cupric oxide is reduced to the cuprous state, but 

 this diffuses to the surface and is reoxidised by the atmospheric 

 oxygen. The tests show that the depolarising liquid serves for 

 several discharges without renewal in any way, and the constancy 

 of the E.M.F. during discharge is very good. The slatting 

 E.M.F. is about i'25 volts, and this falls slowly to about 078 

 at the end of twenty or thirty days; the internal resistance is 

 about 25 ohms. If the air is kept from the depolariser, the 

 E.M.F. falls considerably, but recovers on its being readmitted. 



The Cambridge Scientific Instrument Company has sent 

 us a pamphlet on the measurement of temperature by 

 electrical means, which describes the different types of re- 

 sistance and thermoelectric thermometers which they manu- 

 facture. These thermometers possess the advantage, nut only of 

 being suitable for measuring any temperature up to 1000" C. or 



NO. 172/, VOL. 67] 



1500" C, but also of enabling the reading to be made at any 

 distance from the place at which the high temperature exists. 

 They thus do for thermometry what electrical instruments have 

 done for electrical measurements ; it is possible, for example, to 

 read the temperature, say, of a hospital ward in the engine- 

 room instead of in the ward itself, just as it is possible to read 

 in the central station the electrical pressure at the consumers' 

 terminals. The apparatus described in the list before us ranges 

 from the simple thermoelectric couple or resistance wire in a 

 suitable protecting tube to the elaborate Callendar recorders. 

 Instruments reading direct in degrees centigrade can be supplied 

 with the thermometers. The different purposes for which electric 

 thermometry is the best, and often the only, means of measuring 

 temperature are too numerous to mention ; the convenience and 

 high accuracy of the method will further recommend it to all 

 who have under their control operations involving temperature 

 regulation. 



Readers of Nature are familiar with the work which has 

 been done by Prof. Kahlenberg tending to disprove the dis- 

 sociation theory of electrolysis. A short paper summarising the 

 principal arguments against the theory was read by Prof. 

 Kahlenberg before the American Electrochemical Society last 

 April. We commend this paper to all interested in electro- 

 chemical theory, especially to those who believe firmly in 

 " ionisation." Briefly, the charges against the hypothesis of 

 Arrhenius are the following. The very generalisation which 

 gave birth to the theory, that abnormal osmotic pressure indi- 

 cated an electrolyte, and the converse, has not been supported 

 by further experiment. The theory, if it accounts for any- 

 thing, only accounts for the behaviour of dilute solutions, and is 

 consequently of very limited applicability. There is no ex- 

 perimental evidence, worthy the name, justifying the application 

 of the theory to fused electrolytes. There is no question but 

 that these charges are well supported, and that the ionic theory, 

 if it has given rise to much useful work, has also greatly checked 

 development in some directions, notably that of research with 

 concentrated solutions. It is also a regrettable fact that writers 

 on electrochemical subjects seem to take a pleasure in expressing 

 facts in terms of the ionic theory when there is absolutely no 

 necessity for so doing, which, doubtless, to the non-discerning, 

 gives confirmation, in reality fictitious, thereto ; without going so 

 far as Prof. Kahlenberg and asserting that the doom of the 

 dissociation hypothesis is already sealed, we believe that those 

 who write in this way are running a great risk of rendering their 

 contributions unintelligible to future generations of electro- 

 chemists. 



Statistics of the mineral production in India for the years 

 1S92 to 1901 have been issued by the Depaitment of Revenue 

 and Agriculture (Calcutta, 1902). The output of coal has in- 

 creased from 2i to more than 6i millions of tons. In the same 

 period, the production of gold has trebled, being 53 1 ,766 ounces 

 in 1901, the value being about two millions sterling. 



We have received the general report by the director, Mr. 

 C. L. Griesbach, on the work of the Geological Survey of India 

 for the year ending March 31, 1902. There are brief reports on 

 the field-work carried on in the Madras Presidency, in Burma, 

 Assam, the Punjab, the Himalayan Ranges, Baluchistan and 

 Sind. Inquiries into the occurrence of gold, copper and coal 

 were made in certain districts, without, however, any important 

 economic results. Some of the so-called old workings for gold 

 which abound in Chota Nagpore are nothing more than old 

 prospecting shafts and trenches, and were probably abandoned 

 without the discovery of any paying reefs. One narrow reef 

 gave encouraging results, but only a small outcrop was observed. 

 Prof. R. Zeiller has completed a report on the flora of the Lower 



