March 1st, 1887.] 



SCIENTIFIC NEAVS. 



19 



sidered by many a retrograde step towards a more unen- 

 lightened epoch when armour-plates were carried from 

 stem to stern. The power of modern guns is so enormous, 

 say some, that it is useless to try to keep out projectiles 

 along the whole length of the ship. We cannot protect 

 flotation, or rather stability, by armour. A fighting ship 

 must take her chance in war, trusting to speed, ease in 

 manoeuvring, and the skill and courage of her crew and 

 officers. Armour on her sides is, or ought to be, as abso- 

 lute as armour on the breast of a soldier: both alike doomed 

 by the higher penetrative power of the weapons opposed 

 to them. In the meantime much can be done by armour 

 for the protection of magazines, machinery, and gun posi- 

 tions, " the vitals," as they are termed ; and, above all, an 

 armoured deck can be run the whole length of the ship, whilst 

 subdivision by water-tight compartments will do much to 

 minimise the danger from penetration. 



Such, roughly, are a few of the elements which underlie 

 the science of war-ship design — problems which we may well 

 hope never to see brought to a practical solution. 



The Welsbach Incandescent Gas Burner. — It will be 

 remembered that at the last meeting of the British Associa- 

 tion, Mr. Conrad Cooke described in Section G the system 

 of gas-lighting introduced by Dr. Auer von Welsbach, of 

 Vienna. We understand that several public buildings in 

 Vienna are now lighted satistactorily by this system, and 

 recently a public exhibition of it on a large scale was made 

 at the Marlborough Gallery in London. We have not seen 

 a photometric test of the lamp, nor a measurement of its 

 gas consumption, but, speaking generally, it appears to us 

 superior to such lamps as Lewis's with platinum gauze, and 

 Clamond's with a cage made from a preparation of magnesia. 

 All are alike in principle, so far as the production of light 

 by means of the incandescence of a refractory substance is 

 concerned ; but the Welsbach gauze, or " mantle," as it is 

 called, is more easily raised to a white heat, and therefore 

 requires a smaller consumption of gas. The mantle is 

 formed by dipping a piece of cotton net into a specially- 

 prepared solution containing oxides of zirconium and other 

 iDodies ; it is then dried, and on being held over a Bunsen 

 flame the cotton is burnt, and there remains a network of the 

 incombustible oxides originally contained in the solution. The 

 mantle is then ready for use, and on being suspended over 

 a special form of atmospheric burner, fitted with a glass 

 chimney, it becomes powerfully incandescent and emits a 

 pleasing white light. Moreover, it is stated that by this 

 system a light equal to 20 standard sperm candles can be 

 produced with a consumption of only 2^ cubic feet of gas 

 per hour. If this is found to be so in practice, and if the 

 mantle is able to stand the rough test ot ordinary use, it 

 will doubtless be very largely adopted for shops and houses. 

 We believe it is not recommended for use outside buildings, 

 because it requires a glass chimney and is rather susceptible 

 to air currents ; but even this defect may be overcome as 

 the invention is developed. 



The Royal Gardens, Kew. — It is proposed to issue from 

 time to time, as an occasional publication, notes, too detailed for 

 the annual report, on economic products and plants to which the 

 attention of the staff of the Royal Gardens has been called in 

 the course of correspondence, or which have been the subject of 

 particular study at Kew. It is hoped that these notes will serve 

 the purpose of an expeditious mode of communication to corres- 

 pondents in distant parts of the Empire and be of service to the 

 general public. The first number of the " Bulletin of Miscel- 

 laneous Information," as the publication is called, has been issued, 

 and contains letters and extracts on teff (eragrostis Abyssinica) 

 and oil of ben. 



The International Statistical Institute will hold a meet- 

 ing in Rome during Easter week. 



THE CONVERSION OF HEAT INTO 

 WORK. 



THE present century is distinguished by the rapidity 

 with which the application of heat to the service of 

 man has been extended. At the same time, most 01 the 

 inventors of heat-engines and furnaces have been so ignorant 

 of the principles upon which the action of their inventions 

 depended that lamentable errors have been the conse- 

 quence. The author of a small book on the " Conversion 

 of Heat into Work"* takes these facts as his text, and 

 produces an instructive and useful work ; with only one 

 questionable feature, to which reference will be presently 

 made. The author of this book, Mr. William Ander- 

 son, is, however, by no means content to point out past 

 shortcomings ; but, step by step, he explains, in a simple 

 and interesting way, the various laws on which the true 

 understanding of the conversion of heat into work depends. 

 The phenomena discussed are familiar to physicists, but 

 for those who have not already studied the subject, a prac- 

 tical handbook of this kind cannot fail to be of use. Some 

 of the questions involved are necessarily difficult, but it is 

 well worth an effort to overcome their intricacies, not only 

 for the practical engineer who seeks to improve the design 

 ofa boiler or engine, but for others who should learn to 

 appreciate the great principles involved. 



Within the limit of this short notice we are unable to 

 treat in detail the author's statements, but we cannot refrain 

 from pointing out one serious error into which he has 

 fallen. Notwithstanding his own clear exposition of the 

 laws of thermodynamics in the early chapters, in which he 

 shows that the efficiency of a heat-engine depends on the 

 difiercnce between the initial and final temperatures of the 

 working fluid in the cylinder; yet when he describes the 

 actual steam-engine he makes the extraordinary statement, 

 that there is no fall of temperature in the cylinder, and 

 that none of the heat of the steam is converted into work. 

 Moreover, he leads us to suppose that the air in a hot-air 

 engine, and the mixture of gases in a gas-engine, behave in 

 a similar manner. lie admits that they all expand, and 

 that in expanding they drive out the piston and do useful 

 work, and yet he infers that they are able to do so without 

 loss of heat. Were this really the case it would be a start- 

 ling discovery, and would entirely upset the best teaching 

 of the day. It is, indeed, unfortunate that the author should 

 be the first to gainsay the principles so clearly described in 

 the early part of his own book, as in other respects his 

 teaching is at once sound and easy to follow. Possiblj', 

 however, the error we have pointed out is merely due to 

 inadvertence or imperfect definition. 



Drilling Holes in Plate Glass. — In a discussion on the 

 above subject, recorded in the last volume of the " Transactions 

 of the American Society of Mechanical Engineers," several 

 methods of drilling holes in plate glass were mentioned. The 

 following appear to be the most successful ; — i. Holes .V', in 

 diameter in plate glass \" thick, can be made with an ordinary 

 bow drill, spirits of turpentine being used as a lubricant. The 

 hole should be drilled from one side until the drill has just 

 perforated the glass ; the glass should then be reversed and 

 drilled from the other side. 2. Holes ^\" in diameter in glass J" 

 thick can be made with a brass tube drill, with fine emery as 

 the cutting agent. The drill is run at a speed of 2,000 revolu- 

 tions to the minute, with water as a lubricant. The drilling of 

 forty such holes uses up about one inch of the tube. The well- 

 known sand blast was also referred to, but this is only suitable 

 for work on a large scale. < 



* On the Conversion of Heat into Work ; a Practical Handbook on 

 Heat Engines. By Wm. Anderson, M.Inst.C.E. London : Whittaker 

 and Co , and George Bell and Sons, 1887. I'rice 6s. 



