594 



NA TURE 



[August i6, 1894 



already been acquired, forming as they do a compact and 

 clearly expressed synopsis of the suhject. Another useful 

 feature in the numbers under consideration are tables of physical 

 qaantities, such as the electromotive force of different cells, 

 specific resistance of solids and liquids, the temperature co- 

 efficient being in most cases given as well as the temperature 

 at which the value of the resistance given is measured, together 

 with the observer's name. An elaborate scheme of prefixes 

 nsed to denote multiples and submultiples of the different 

 units is given, which, as long as the scheme is printed on the 

 opposite page to the table in which these prefixes are used, 

 saves a good deal of space, but will probably cause a great deal 

 of unnecessary confusion if they are used in other parts of the 

 work, unless the value is in every case also given in the index 

 notation. 



In a short communication, made to the French Academy of 

 Science, M. Moureaux says that on examining the magneto- 

 graph records of the Pare Saint-Maur Observatory for the night 

 of July 11-12, he finds a disturbance which corresponds in 

 time with the earthquake shock that caused so much destruc- 

 tion at CoH'itantinople. As M. Moureaux has taken the pre- 

 caution to have non-magnetic copper bars suspended alongside 

 the magnetograph needles, and the records from these bars 

 show no disturbance, it is evident that the effects observed were 

 due to magnetic causes, and not to a mechanical shock. As 

 the magnetic disturbance occurred sixteen minutes before the 

 time at which the earthquake shock was felt at Constantinople, 

 and since the two places are separated by a distance of 3000 

 kilometres, it would appear that the disturbance travelled at 

 the rate of only three kilometres per second. This is certainly 

 a very slow rate of propagation, and it would be of great 

 interest if the observers at other observatories where a 

 permanent magnetic record is kept, were to examine their 

 curves, and see whether they show a similar disturbance, and 

 if so, if the rate of propagation is about the same as the above. 

 If the values obtained vary much, it is probable that the dis- 

 turbance noted by M. Moureaux was of solar rather than of 

 terrestrial origin, or at any rate was not connected with the 

 earthquake at Constantinople. 



Anything respecting Corea is of special interest at the 

 present time, and the short article on the "Cultivation of Cotton" 

 in that little-known country, which a recent number of the 

 Journal of the Society of Arts contains, is certain to have many 

 readers. According to this article, which is based upon a re- 

 port of the Commissioner of Corean Customs at Fusan, the total 

 area under the cultivation of cotton in Corea is roughly com- 

 puted to be 872,<x)o acres, the yield of seed cotton from which 

 per annum is put at 1,200,000,000 lbs. The yearly consumption 

 of "cleaned" or raw cotton is estimated at 300,000,000 lbs. 

 The Corean fibre is reported to be superior to that produced in 

 Japan. The method of cultivation is as follows : — The 

 ground is usually ploughed up during the early winter, and 

 allowed to remain in this condition until the frost is well out of 

 it, when it is broken up with a hoe, and manure, mixed with 

 wood ashes, spread over it. The fields are now ready for the 

 reception of the seed, which is generally sown about April to 

 May. The seed, of which there is but one kind, is not placed 

 in drills, a« is done in Japan, but is sown broadcast, and then 

 trodden in and covered up with the feet, sesamum seed being 

 very often sown in the same field with it. The young shoot 

 shows above ground about the tenth day, and at maturity attains 

 a height of from 2 feet to 2i feet. The plant blossoms in 

 August, and on an average bears forty pods, each containing 

 four cells, at a rule within a double capsule. The gathering of 

 the crop, which begins about October, continues until frosts sets 

 in, some time in November. No attention is paid or .skill dis- 

 NO. 1294, VOL. 50] 



played in the cultivation once the seed is in the ground ; every- 

 thing is then left to nature. No further manure is added, nor 

 are they ever thinned out or given water in times of drought. 

 The crops are principally gathered by women, who also are 

 largely employed afterwards in separating the seed. 



During the last few years, alloys of tin and lead have beeD 

 employed in manufactures in which the constancy of melting 

 points after successive meltings played an important part. 

 Rudberg, one of the earliest workers in this field, noticed that 

 the thermometer stopped at two points during the solidification 

 of these alloys ; the higher point varied with their composition, 

 while the lower was constant, being about 187°, and was iden- 

 tical with the melting point of the " chemical alloy " represented 

 by the formula PhSn,. In the current number of Wiedematin s 

 Annalen, Bernhard Wiesengrund gives the results of a complete 

 series of experiments with tin-lead alloys ranging from PbSnu to 

 PbjjSn. They were melted in a crucible of sheet iron covered 

 with a lid provided with two brass tubes to admit and withdraw 

 dry hydrogen during heating. An iron tube closed at the bottom 

 was attached to the lid. It dipped into the alloy, and served to 

 contain the thermometer, the bulb of which was surrounded by 

 mercury. The thermometer was gradu.ited from 0° to 360° C, 

 and contained nitrogen above the mercury column. The crucible 

 was surrounded by a sheet-iron water-jacket kept at 150' C, 

 and the heating was done by means of a triple Uunsen burner. 

 As regards the densities of the alloys, it was found that they 

 were all lighter than might have been expected from the 

 densities of their constituents. This increase of volume was 

 greatest in the case of the " chemical alloy " PbSnj, and de- 

 creased as one or the other constituent preponderated. The 

 process of solidification showed Uudberg's two points distinctly. 

 The higher one, called the melting point, was really a point at 

 which the cooling became somewhat less rapid. The lower, 

 called the point of solidification, w.as a truly stationary point, 

 except in the alloys containing much lead. The most regular 

 curve of cooling is shown by the alloy PbSnj. At about 178' 

 there is a dead stop lasting for seven minutes, not preceded by 

 a perceptible stop at the melting point. The latter becomes 

 more pronounced as the percentage of tin increases, and appears 

 as a point of inflexion in the alloy PbSn,;. .'\s the lead is 

 increased, the melting point rises, the point of solidification falls 

 slightly and becomes less pronounced, and .ill breaks in the 

 curve of cooling tend to disappear. The author gives a plausible 

 explanation of the phenomena analogous to the theory of salint 

 solutions, tin being regarded as the solvent. After twenty-four 

 successive remeltings a mechanical rearrangement was observed, 

 producing a slight elevation of the fusing point and an ap- 

 proximation of the point of solidificition to that of the 

 "chemical alloy." This w.is due to the excess of the heavy 

 lead, or the light tin gradually separating out from the alloy 

 PbSn,. 



The Transactions and Proceedings of the New Zealand 

 Institute (vol. xxvi. ), containing papers re.id before the Institute 

 during 1893, has been published, and is obtainable from 

 Messrs. Triibner and Co. 



"Xnv. Quarterly fournal ol the Geological Society (No. 199, 

 August) has been issued. It contains five plates, illustrating ' 

 papers by Mr. A. Marker, Mr. \V. \V. W.ntts, Mr. Frank 

 Kutley, and Sir J. W. Dawson and Dr. W. Hind. 



The August number of the Journal of the Royal Micro- 

 scopical Society is almost entirely taken up with summaries of 

 current researches. The only two papers arc liy Mr, F. Chap- 

 man and Mr. T. Comber, the former dealing with the fora- 

 minifera of the gault of Folkestone, and the latter with the 



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