I 



420 



NA TURE 



[August 22, 1907 



'I'lin important position occupied by llio ilcctric spark 

 in wireless telcj^rapliy will account for the nuiny atlempls 

 which have been made in recent years to obtain some 

 knowledge as lo its effective resistance. The principal 

 methods used fall into two groups, based either on the 

 original resonance arrangement of Bjerkncs or on the 

 substitution process of Simons. Unfortunately, llie two 

 groups i>ivp different results, and Dr. W. Kickhoff has 

 rendered valuable service by his examination of the 

 v.ilidity of the various methods which appears in the 

 rhysihalisclic ZeitschrijI for August I. He comes to the 

 conclusion that deductions as to the most suitable arrange- 

 ments for telegraphic purposes cannot legitimately be 

 made from results oljl.-iined by the melhiid of Simons. 



Tmk memorandum of the Manchester Steam Users' 

 .Association for the year 1906 consists mainly of a report 

 on the tests of pressure gauges carried out at the National 

 Physical Laboratory and the remarks of the chief engineer 

 of the association on these tests, and on pressure gauges 

 in general. The ten gauges tested were all by trust- 

 worthy makers and of first-class workmanship, and the 

 report of the tests states that, as regards freedom from 

 friction and backlash, they leave little to be desired. 

 Greater agreement between the records at different 

 temperatures ought to be aimed at, and for gauges sub- 

 ject to vibration some form of balancing should be adopted. 

 The whole report will be of great value to pressure-gauge 

 makers, and may be taken as a typical illustration of the 

 way in which improvements can be brought about by the 

 cooperation of manufacturers and an institution like the 

 National Physical Laboratory. 



Dr. C. Xoki>m.\n\, of the Paris Observ.-itory, published 

 several years ago in the AnnaUs de I'Obscrvaloire de Nice, 

 vol. ix., a theory of the diurnal variation of terrestrial 

 magnetism, according to which the convection currents of 

 the upper atmosphere, crossing the lines of magnetic 

 force, generate electromotive forces which, in a region 

 rendered conducting by solar radiation, produce electric 

 currents and so affect the magnetic needle. In the 

 March number of Terrt'slrial Magnetism he shows that 

 the observations he made in Algiers during the total solar 

 eclipse of August 30, 1905, confirm a deduction from his 

 theory, namely, that during an eclipse the magnetic needle 

 should lend to return from its normal position at the time 

 of occurrence of the eclipse towards its mean posilion for 

 the day. 



Paris i. and ii. tcomprising ;,;,5 pp. and iS plates) of 

 vol. ■ l.xxxvii. of the Zcitschrift fiir -tvisseiischafllichc 

 Zoologie are occupied by an elaborate paper on the com- 

 parative developmental history of sexual individuals in 

 the hydroid polyps. The author, Mr. A. Goetle, of Strass- 

 burg, formulates some important conclusions with regard 

 to this development, which are, however, loo complex to 

 be summarised within our limilations of space. 



In a paper on the navicular of the tarsus of man and 

 monkeys, published in vol. xli., part iv., of the Journal 

 of Anatomy and I'liysiology, Mr. T. Manners-Smith 

 describes and illustrates the remarkable variations obtain- 

 ing in that bone in the human subject. In some degree, 

 at any rate, these variations appear to be connected with 

 the degree of mobility of the foot, certain features being 

 more constantly developed in, this bone in the skeletons 

 of ancient Egyptians than among modern Europeans. The 

 occasional existence of a separate element in the tuberosity 

 of the navicular is also noticed. 



NO. 1973. VOL. 76] 



Fko.m the asldundieg feat ac( umplish. <l by Prince 

 Borghese in his wonderful journey in a motor-car from 

 Pekin to Paris, many lessons mav be drawn. The 

 greatest, the Engineer of August 1(1 points out, is the 

 wonderful adaptability of the power-driven vehicle. The 

 distance traversed is estimated at 7000 to 8000 miles, and 

 the time occupied was sixty-two days, the daily average 

 being about 121 miles. When the time is taken off for 

 pulling the car through loo,se sand and for extricating it 

 from morasses, the speed seems almost incredible, con- 

 sidering that for half the journey there were practically 

 no roads. .Serious obstacles were encountered. Over- 

 whelmed in a cyclonic sandstorm, dragged through rivers, 

 precipitated from a weak bridge into a fast-running river 

 below, immersed in bogs, the wood-work of the car on 

 lire, and being nearly run into by a train on the Trans- 

 Siberian Railway, were a few of the experiences of the 

 intrepid traveller, ;my one of which would be sufficient to 

 slop most people from continuing such a perilous journey. 



O.x .August 17, 1.S0;, Robert Kullon's steamer, the 

 Clermont, ran her trial trip from New \'ork to Clermont, 

 and in order to commemorate the centenary of steam 

 navigation, an interesting account is given in the Engin.'rer 

 of August :6 of the events that led up to this develop- 

 ment. Illustrations are given of the paddle-wheel steam- 

 boat Clermont .and of her machinery. 



Tiiii prospects of the Indian manganese ore induslrv 

 are discussed by Mr. A. Ghose in the Journal of the 

 Society of Arts (August 2). The demand (cr Indian 

 manganese ore has grown with great r.ipidily. In 1905 

 the export to Great Britain amounted to 71,6110 tons, 

 whilst last year the total amounted lo 490,012 tons, valued 

 at 865,443;. India supplied most of the manganese ore 

 used in the British furnaces, Brazil WNlh 127,257 tons 

 being second, and Russia following with 103,27(1 tons. 



An interesting account of the Museum of Traflic and 

 Engineering at Berlin is to be found in the August 

 number of the Engineering Magazine. The museum is 

 located in the old Hamburg passenger railway station, 

 which has, however, been thoroughly reconstructed for 

 til.; purpose so f.ir as its basement is concerned. The 

 museum has three main departments, devoted 10 railway, 

 naval, and civil engineering respectively. Explanatory 

 notes are added lo many of the. exhibits, and in some 

 instances a cross-section is given to illustrate ihe internal 

 arrangement. .Sonic of the models may be worked by 

 visitors, and to these a special notification is attached. 

 .Models of plant of exceptional interest are to be demon- 

 strated and explained from time to time by ofiicials of 

 the institution. In addition to models, the museum 

 possesses many diagrams, photographs, statistical tables, 

 a reading room, and library, all of which should make it 

 of real scrviie to engineers. 



The extension section of the Manchester Microscopical 

 Society has sent us its new list of lectures arranged for 

 delivery by members of the society during the coming 

 winter in Yorkshire, .Manchester and district. The work 

 of lecturing and di'monstrating is entirely voluntary and 

 giatuitous on the part of the members, but a charge is 

 made for the hire of slides, travelling, and out-of-pocket 

 expenses. The purpose of the section is to bring scientific 

 knowledge, in a popular form, before societies unable to 

 pay large fees to professional lecturers, but In all cases 

 where lectures are given before societies which are com- 

 mercial undertakings, or .are subsidised out of fiovern- 



