5H 



NATURE 



[August 29, 19 18 



addition of the second winding on the same armature 

 core, a high-tension magneto was evolved. 



To the Bosch Company, of Stuttgart, belongs the 

 credit of having established the fact that a high- 

 tension magneto can be manufactured on a commercial 

 basis to give trustworthy and efhcient ignition in prac- 

 tice. Although this important industry was allowed 

 to develop in Germany, the modern high-tension mag- 

 neto was first conceived in France by M. Boudeville, 

 who, unfortunately, omitted to include a condenser in 

 his scheme for eliminating sparking at the contact 

 points. A condenser is a vital part of every magneto ; 

 without it the machine would be quite impracticable. 

 It is surprising that M. Boudeville should have over- 

 looked this feature, because, here again, the idea of 

 using a condenser for such a purpose is of French 

 origin, Fizeau being the first to suggest, in 1853, con- 

 necting a condenser in parallel with the contacts on a 

 Ruhmkorff coil to prevent excessive sparking. 



The magnetos made in this country vary somewhat 

 in design, being based to some extent on the original 

 Bosch model with improvements in many respects. 

 Thus the trouble which was experienced with the 

 original Bosch D.A.L. design of misfiring has been 

 completely removed in a machine of the rigid armature 

 single-cylinder type intended for use on rotary engines 

 like the Gnorrie. The Bosch Z.U.4 machine was 

 formerly extensively used in this country. The design 

 or this has been considerably simplified, chiefly in 

 respect of construction of the bearing for the half- 

 speed wheel. An 8-cylinder sleeve-inductor magneto 

 with fixed armature, now made in this country, is 

 designed to give four sparks per revolution, and is 

 therefore fundamentally different from the ordinary 

 rotating armature type, which cannot give more than 

 two sparks per revolution. The sleeve-inductor rotates 

 at engine speed, whereas, in the case of a 6-cylinder 

 machine built on the same principle, it runs at three- 

 quarters engine speed. 



In a single machine of the 8-cylinder type there are 

 860 parts, no fewer than 397 of which are of different 

 design. The manufacture is therefore attended with 

 considerable difficulties, and can be undertaken suc- 

 cessfully only if highly skilled labour is available and 

 the component parts are all machined to extremely 

 fine limits. The fact that these magnetos are being 

 produced in very large quantities is evidence that the 

 difficulties are being overcome. A magneto of the 

 polar induction type, also developed in this country, 

 is intended more especially for 12-cylinder work. This 

 is probably the first 12-cylinder model developed and 

 standardised in this country. The machine is in- 

 herently of much simpler design than the sleeve-in- 

 ductor machine, because the latter, which on account 

 of its design is very difficult to manufacture, is 

 replaced by a polar inductor which is designed to 

 be easily made, and is at the same time a more 

 rigid and trustworthy mechanical structure. Other fea- 

 tures combine to simplify the manufacturing problem 

 greatly. 



No matter for what purpose a magneto is to be used, 

 the chief feature must be trustworthiness, and this, is 

 possible only if the design is good, the materials are cor- 

 rectly chosen, and the workmanship is perfectly sound. 

 Of the first- and last-mentioned conditions there can 

 be no question. With regard to the choice of materials, 

 the development of both the metallic and non- 

 metallic industries has left it bevond doubt that such 

 materials will be available. ^he improvement in 

 foundry methods has resulted in the regular supply of 

 trustworthy aluminium castings ; in steels important 

 advances have been made, which now give the required 

 strength w^th a minimum weight of material. Die- 

 castings made of an aluminium alloy containing no 



NO. 2548, VOL. lOl] 



zinc are a great advantage. The manufacture of die- 

 castings was formerly neglected here, but British pro- 

 ducers are now devoting their attention to the subject, 

 with the result that there is available an adequate 

 supply of these castings. The advantage of die-castings 

 over sand-castings is that the amount of machining 

 that has to be performed on the parts is very much 

 reduced, the metal is much tougher, and the threads 

 in tapped holes are not so likely to become stripped 

 when the screws are securely tightened. With regard 

 to non-metallic materials, the most important require- 

 ments are insulating materials, comprising varnished 

 silk, cambric, and paper. These insulating materials 

 are essential to the manufacture of a satisfactory mag- 

 neto armature, and although they can be purchased in 

 England at the present moment, a fair portion is still 

 imported. It is probably correct to say that the small 

 extent of the magneto industry contributed in a large 

 measure to the backward state of the insulating 

 material industry in this country, in regard not only to 

 paper, silk, and cambric, but also to moulded insu- 

 lating material comparable with " stabilite." a German 

 product. Now, however, this industry is becoming 

 firmly established. Here, again, we have an impres- 

 sive example of the effect of one industry upon another. 

 The magneto industry itself is of sufficient importance 

 and magnitude to be regarded as a "kev" industrv. 

 With its development there has been established a 

 number of new industries concerned with the supply 

 of component parts. The manufacture of insulating 

 materials, varnish, platinum-iridium or tungsten con- 

 tacts, aluminium-copper die-castings, special steels — 

 these industries either did not exist at all in England, 

 or else were of only small dimensions. Each of 

 them has now become an important British industry, 

 largely in consequence of the home production of mag- 

 netos. Even if the British Science Guild had done no 

 more, its achievement in pressing home this fact 

 through the medium of the exhibition at King's College 

 would entitle the Guild to the thanks of the nation. 



Electron. 



WEATHER INFLUENCES ON O PER ACTIONS 

 OF WAR. 



AN. article on "Weather Controls over the Fighting 

 during the Spring of 19 18," by Prof. Robert 

 deC. Ward, appeared in the Scientific Monthly for July. 

 Such vast interests are at stake in the present war 

 that any factor which can help or hinder is of im- 

 mense importance. The part played by meteorological 

 controls is set out by the author as fully as is possible 

 at the present time, leaving fuller information for a 

 later date. 



In the Western war zone the season of aggressive 

 operations has generally been from April to November. 

 The offensive on the part of the enemy began this 

 year on March 21, and the author states that "the 

 time must have been carefully chosen after consulta- 

 tion with the meteorological experts. It was a spell 

 of fine, dry weather." Easterly winds usually accom- 

 pany such spells, and these are " favourable for the 

 use of gas by the enemy and also carry the smoke of 

 artillery firing to the west, thus helping to screen the 

 attacking troops." A thick fog also favoured the 

 attack, and "the Allied gunners could scarcely see 

 their own horses " ; the author mentions that " the 

 surprise of the British Fifth Army was largely attributed 

 to the fog." In the opinion of the present writer, no 

 meteorologist could have foreseen with any reasonable 

 certainty such favourable weather conditions. A 

 change to less settled weather occurred at the end of 

 the month; and it proved very favourable to the Allies, 

 whilst " the Germans were at once greatly handicapped 



