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NA TURli 



[Mav 24. 1900 



A BACTERIOLOGICAL method of exterminating rats, proposed 

 by M. J. Danysz of the Pasteur Institute of Paris, is described 

 in the British Medical Journal. M. Danysz has found a 

 microbe which, if introduced into a population of rats, may be 

 trusted to breed a pestilence among them that will wipe them 

 out, or at least make them a nejTligihle quantity. From field- 

 mice suffering from a spontaneous epidemic disease he isolated 

 a cocco-bacillus presenting the general characters of B. coli, and 

 thus resembling Lceffler's B. typhi vmrtuin. By an elaborate 

 process of repeated cultures of this micro-organism passed through 

 series of mice and afterwards through rats, he succeeded in intensi- 

 fying its virulence so as to make it, when eaten, certainly patho- 

 genic for the latter rodents. Having satisfied himself of the 

 fatal effect of the cultures in the laboratory, he had them tried 

 in a large number of farms, warehouses, and other places in- 

 fested by rats. From the reports of these experiments, amount- 

 ing to several hundreds, it appears that in 50 per cent, of cases 

 the method resulted in a complete disappearance of the rats, 

 while in 30 per cent, their number notab'y diminished ; in 

 20 per cent, the method failed. 



Some interesting figures showing the high estimation in which 

 technical knowledge is held in certain branches of industry 

 by German manufacturers, have recently been published in 

 the Zeitschrift filr angewandte Chcmie, from a lecture on 

 " Technical Education and the Importance of Scientific 

 Training," delivered before the German Emperor by Prof. J. 

 Bredt. The following statistics, corrected to the end of last 

 year, refer to three of the most important factories in Germany 

 where aniline dyes are made, viz. the Badische Anilin-und 

 Sodafabrik, of Ludwigshafen ; the Farbewerke vorm. Meister 

 Lucius und Briining, of Hochst am Main; and the i^arben- 

 fabriken vorm. Fr. Bayer and Co., of Elberfeld. 



Of course, the Engineer remarks, conditions are somewhat 

 different in Germany from those which obtain in this country, 

 because these dye works own the patents for various highly 

 lucrative proprietary articles, and manufacture numerous 

 pharmaceutical preparations ; but we should be interested to 

 iearn how many " chemical " factories in Great Britain employ 

 over 100 skilled chemists. 



An enterprise, similar to the Edison works at Paderno, where 

 energy of some 13,000 horse-power is derived from the River 

 Adda, and employed for producing electricity, which is carried 

 by overhead cable to Manzo and Milan, but on a larger scale, 

 is, states the Board of Trade Journal, now on the eve of 

 completion in Northern Italy. A report of H.M. Consul at 

 Milan ^Foreign Office, Annual Series, 2413) states that the 

 Societa Lombardia per distribuzione di energia Elettrica, 

 obtained a concession from the Government on the River 

 Ticino, at Vizzola, some miles below its issue from Lake Mag- 

 giore, and immediately set about constructing works for the 

 • development of hydraulic power of no less than 20,000 horse- 

 power (theoretical), which will give 10,000 effective horse-power 

 of electric energy for industrial purposes, after making full 

 allowance for loss in transmission; Since the works were begun, 

 the sanction of the Governrrfent has been obtained to a project 

 for the construction of a movablt dam across the river some 

 distance higher up, which would enable the company to 

 increase its volume of water, and allow of the same being 

 constantly maintained during all seasons of the year. The 

 theoretical hydraulic power would then be 24,000 and the 

 effective electric energy 12,000 horse-power. This dam has 

 NO. 1595. VOL. 62] 



not yet been commenced, but the works hive been constructed 

 on the basis of the larger supply of water. Seven turbines and 

 seven dynamos, giving three-phase alternating currents, have 

 been put up. The dynamos and all the other electrical plant 

 have been supplied by Germany. It was originally intended 

 to bring all this electric energy into Milan, a distance of 

 twenty-five miles, but the whole of it has now been disposed of 

 in and about the manufacturing towns of Gallarate, Busto, 

 Arsizio, Legnano and Sarsuno, which lie between Vizzola and 

 Milan, a district which already, for the cotton industry alone, 

 uses steam to the extent of 10, coo horse-power. This enter- 

 prise is .said to be the most important of its kind in Europe. 

 The plans are due to the initiative of Italian engineers and 

 were made as far back as 1887, but their execution must be 

 attributed in a large measure to the assistance of a German 

 firm which has subscribed a considerable part of the capital of 

 the company. 



In a recent number of Nature (March i, p. 421) reference 

 was made to a paper by Dr. Liideling, in which diurnal varia- 

 tions of terrestrial magnetism were shown graphically " with the 

 aid of von Bezold's vector diagrams." Though von Bezold 

 appears to have been the first to use the convenient term 

 " vector diagram " to designate the curves referred to, Dr Chree 

 pointed out in Nature of March 22 (p. 490) that the curves 

 were employed by Airy in 1863, and since then by several 

 people in this country, including Lloyd and himself, and were 

 not used by von Bezold until 1897. Dr. Liideling now sends us 

 a letter in which he states that both von Bezold and himself 

 were well aware of the previous use of the curves, and that 

 acknowledgment of earlier work was made in the paper briefly 

 mentioned in Nature. 



Prof. J. Joly has discussed " The Theory of the Order of 

 Formation of Silicates in Igneous ^ocV.i,'''' {Proceeiings, Roy. 

 Dublin Soc. ix. [N.S.] 1900). He has lately found that the 

 softening point of quartz is far below what is currently thought. 

 Observations indicate that silica is a body possessing an extra- 

 ordinary range of viscosity. It is a thick liquid at about 1500' C. 

 At a temperature of about 800° C. it is plastic, and yields with 

 considerable rapidity to distorting forces. Perhaps it never 

 crystallises very vigorously. The author's experiments show 

 that a silicate containing a small quantity of silica crystallises 

 out at a higher temperature than a silicate with a larger per- 

 centage of silica ; and this, according to his theory, is because 

 the crystallising point of the one is less affected by the silica 

 than that of the other. 



In a short article on "The Formation of Minerals in 

 Granite" {Memoirs, Manchester Lit. and Phil. Sjc. xliv. 1900), 

 Mr. C. E. Stromeyer brings forward some facts and suggestions 

 which lead him to conclude that there is no necessity to limit 

 the temperature of granite formation, as propounded by Dr. 

 Sorby, nor to assume that the eirth's interior is solid. Not 

 only temperature and rate of cooling, but also pressure have 

 combined to influence the mineral composition of granites. 

 Where the solid rock resting on the nnlten material is of a 

 low specific gravity and a bad conductor of heat, the depth at 

 which granite rock would commence to solidify would not be 

 great, and most probably the quartz would crystallise first, 

 forming, say, quartz-porphyry. Where the rock resting on the 

 molten mass is heavy, containing perhaps much iron-oxide, and 

 acting as a good conductor of heat, the depth at which the 

 granite would commence to solidify would be much greater 

 than in the previously-mentioned case, the pressure would be 

 much greater, and most probably the quartz would remain fluid 

 long after the felspars had crystallised, forming, say, felspar- 

 porphyry. In the author's opinion, every intermediate condition 

 is conceivable. 



