October 12, 191 1] 



NATURE 



479 



" lay " ; he merely keeps the telescopic sight on the 

 mark and fires as fast as the gun can be loaded — 

 twenty times a minute. He is the pointeur; other 

 gunners attend to laying of the gun, in giving the 

 elevation to correspond with the range finder, and in 

 ! setting the fuse, for which a special instrument has 

 at last been introduced ; others traverse the gun when 

 required and hand over the ammunition, and all can 

 work in security behind a steel shield. But the man 

 who fires the gun gives his individual attention to 

 "pointing." 



Official optimism at the end of the last century 

 had declared our artillery to be perfect — a sure pre- 

 lude to disaster. We know now that it was fit only 

 for the scrap heap, and would have been knocked out 

 in the first encounter with a European Power ; and the 

 German mercenary gunner in Africa was more than a 

 match for our regular artillery. 



We must look to France for the most modern 

 development of artillery science, as our military 

 authority is quite content on a back seat. 



Parts iii. and iv. have the appearance of being lifted 

 from a French source. The territorial gunner will 

 profit at his leisure by a study of these parts and the 

 useful hand sketches ; also in walking over the ground 

 in his neighbourhood with eyes open ; his opportunity 

 of actual insight at manoeuvres will be small. 



The word mobility is always in vogue, with little 

 grasp of its meaning. 



After a war the cry is always for a more powerful 

 gun ; and our eighteen-pounder weighs 24 cwt. on a 

 pair of wheels. This is too much for the road and the 

 team, and is putting the cart before the horse accord- 

 ing to the proverb modified. A field gun must be able 

 to leave the road and cross a ploughed field, so that the 

 old definition of the Act of Parliament of Henry VII. 

 still holds good, of a ton as a cartload, in fixing the 

 standard weight to be carried on a pair of wheels. 



But in a long peace, when smart evolutions are con- 

 sidered of more importance than gunnery, and 

 mobility comes to mean a gallop with no reality be- 

 tween the team, the weight decreases to an opposite 

 extreme. 



The horse scarcity is becoming acute with the ad- 

 vance of the motor-car. Territorial gunners will 

 have to learn their drill indoors with blocks of wood 

 and toy soldiers, like naval officers playing a war 

 game on the gun-room table ; and this book will 

 provide plenty of ideas for abstract tactical problems. 



The artillery tactics of the flying machine come in 

 for discussion. These tactics have been worked out 

 long ago by the French, and the dirigible balloon 

 was directed to take up a place of safety hovering 

 vertically overhead, as then the enemy would not 

 dare to fire with the prospect of the shot descending 

 on his own head or his friends'. 



We prefer to think of the flying machine as a 

 dragon-fly, in the German name, harmless and lovely 

 for our delectation. But no public funds would be 

 available if it could not be shown that the flying man 

 could be utilised for human destruction, employed as 

 " the ligfht militia of the lower skv." 



NO. 2189. VOL. 87] 



G. Greenhill. 



INSULATING MATERIALS AND ARMATURE 

 WINDINGS. 



(1) Les Substances Isolantes et les M&tho&es d'lsole- 

 ment utilisees dans I'Industrie Electrique. By Jean 

 Escard. Pp. xix + 313. (Paris: Gauthier-Villars, 

 191 1.) Price 10 francs. 



(2) Les Enroulements Industriels des Machines & 

 C our ant continu et a Courants alternatifs : Thiorie 

 et Pratique. By E. Maree. With a preface by Paul 

 Janet. Pp. vii + 240. (Paris: Gauthier-Villars, 

 191 1.) Price 9 francs. 



(1) A TREATISE on insulating materials conceived 

 ■i*. in a scientific spirit would certainly be 

 welcome to many electrical engineers, and on reading 

 the author's preface to his attempt to write such a 

 treatise one concludes he has approached his subject 

 from this point of view. He tells us that his work 

 is not intended to be a mere enumeration of the 

 various insulating materials available, but a critical 

 investigation, such as will help the practical engineer 

 to make in each case the best selection possible. 

 Good as the author's intentions were, his perform- 

 ance falls short of them. 



There is, to begin with, a good deal of matter in 

 his book which has nothing whatever to do with 

 insulating materials. The first forty pages are de- 

 voted to a discussion of metallic and liquid conductors, 

 and here we find merely a repetition of statements 

 and figures which will be found in any text-book on 

 physics. This is padding; so is the picture of a 

 drilling machine, that of a shop in which tissue paper 

 is pasted on to transformer plates, and so are the 

 illustrations of various wooden and ferro-concrete 

 teleeraph poles. To drag in the coherer used in 

 wireless telegraphy is also padding, pure and simple. 

 That the insulating properties of concrete are dis- 

 cussed is quite right, but it is misleading to draw 

 any conclusions from it in respect of the insulation 

 of dvnamos. Yet on p. 128 we are told that small 

 machines are generally placed on timber, and are 

 thus sufficiently insulated from earth. Large machines 

 must be put on a concrete foundation, and although 

 this is not an absolute insulator, it is a sufficiently 

 poor conductor to prevent any considerable escape of 

 electricity to earth. But precautions are necessary; 

 the foundation must be kept dry, and to this end 

 one must avoid the neighbourhood of steam and 

 water pipes, and one must dry the air in the engine- 

 house by ventilating fans. How a steam dynamo is 

 to be driven without steam and water pipes coming 

 near it the author does not explain. 



As regards special insulating compositions, there is 

 little more than enumeration accompanied by some 

 general remarks, such as one might find in a trade 

 list. In some cases the composition is given in 

 detail, but no definite electrical data. We find such 

 trade names as " Radoonite," "Terracite," "Re- 

 fragor," " Megotalc," " Micacementite." The lasN 

 mentioned material is said to withstand vibration, 

 and we are told that certain traction motors which 

 were not insulated with it broke down after a run 

 of 20,000 km., whereas after this material was used 



