: 4° 



NATURE 



[May 8, 1913 



in making public the results of their labours in 

 this direction up to the present. Though the 

 book is but a small volume of 140 pages, the 

 matter is greatly condensed, and will demand 

 close attention for its full significance to be 

 appreciated. 



The essential unit of the Holzwarth gas tur- 

 bine consists of a combustion chamber into which 

 gas, or hydrocarbon vapour, and air are delivered 

 at a small pressure by a suitable pump through 

 mechanically operated inlet valves ; ignition is by 

 high-tension magneto, and the resulting high 

 temperature and pressure combustion products 

 then discharge through a spring-controlled flap 

 valve, via a nozzle, to the rotor vanes ; having 

 passed the rotor, the gases enter an exhaust 

 pipe, wherein a partial vacuum is constantly main- 

 tained by an exhauster. Very shortly after igni- 

 tion the flap valve is slowly closed by mechanical 

 means, time being permitted for a gust of 

 scavenging air to pass through, thus cleansing 

 and filling the combustion chamber in readiness 

 for the next working charge of vapour, and cool- 

 ing the nozzle and rotor vanes. The action is 

 thus intermittent, and the design involves three 

 valves in each unit, together with charging and 

 exhausting pumps. In the actual turbine several 

 such units are arranged symmetrically around a 

 turbine wheel or rotor, the continuous speed of 

 which is preserved by the successive impulses 

 thereby imparted to its vanes. As fuels, petrol, 

 kerosene, gas oils, benzol, and even tar oil may be 

 satisfactorily employed. 



The book is divided into four sections, in the 

 first of which a theory of the gas turbine is ex- 

 hibited mathematically by aid of analysis and of 

 entropy diagrams ; much of this part is of the 

 nature of a summary of formula? and results, and 

 cannot be fully appreciated without much reference 

 to other works ; moreover, partly on account of 

 difficulties of analysis, but largely from imperfec- 

 tion of the physical data, some of the conclusions 

 reached are of a very conjectural character, and 

 may require substantial qualification after a more 

 extended practical experience. The author con- 

 siders in detail the several operations of charging, 

 compression, ignition, combustion, expansion, 

 and scavenging; he concludes that the inter- 

 mittent action used, with the lowest possible tem- 

 perature of charge prior to ignition, and the 

 largest possible nozzle opening, is essential to 

 economy, and is conveniently realisable in actual 

 design. Data relative to compression are still 

 wanting, and the investigation given proceeds 

 largely upon assumptions suggested by experi- 

 ence and general knowledge ; in the Holzwarth 

 combustion unit it is not practicable to compress 

 NO. 22/1. VOL. 91] 



to any extent before ignition, but the author is 

 persuaded that satisfactory turbine efficiencies are 

 attainable at much lower compressions than are 

 usual in reciprocating engines. 



An interesting section of the work is that 

 dealing with the utilisation of the exhaust heat ; 

 by aid of a "regenerator," sufficient heat is said 

 to be recoverable to work the charging and 

 exhausting apparatus. 



The construction and details of the actual tur- 

 bine are described, and the text is illustrated by 

 many well-drawn and clearly executed figures. 

 The gas turbine is as yet in its infancy, and it 

 would be unfair at the present time to compare 

 it with the modern reciprocating high-efficiency 

 engine ; in the last section of the book test results 

 are given, together with copious diagrams and 

 tables. Progress is continuing, and further ex- 

 perimentation is needed, and will be carried out by 

 the able author and his business colleague. 



The translator is to be congratulated on his 

 work ; the text is in such good and clear English 

 as to betray no suggestion of its German origin. 

 The book is well printed and illustrated, and from 

 all points of view is a welcome and valuable 

 addition to the literature of the problem. 



(2) This is an excellent elementary text-book 

 on the internal combustion engine, with special 

 reference to the small petrol engine, and forms a 

 suitable introduction to the larger work by the 

 author on the same subject ; though succinctly 

 presented, the matter is never obscure. A brief 

 historical notice is succeeded by an account of 

 the leading facts of the theory of heat and the 

 fundamental formulae of the ordinary theory of 

 perfect gases. The desirable feature appears of 

 a limited use of easy differentials, the several 

 steps of the reasoning being given in full so that 

 the student should experience no difficulty in fol- 

 lowing the argument "to its conclusion ; that 

 nebulous quality, entropy, is also dealt with intelli- 

 gibly, and a useful account is given of indicators 

 and indicator diagrams. The difficult subject of 

 explosion pressures is treated in the light of the 

 results obtained by the Gaseous Explosions Com- 

 mittee, the variability of specific heat with tem- 

 perature being suitably emphasised. This is fol- 

 lowed by descriptions and large sectional views 

 of actual typical engines, including the Diesel and 

 semi-Diesel types, together with illustrations and 

 an account of uncooled and cooled pistons and 

 valves, and a short note on Aero engines. 



Chapter vi. treats more fully of fuels, both liquid 



and gaseous, including alcohol and benzol, and 



the principle of the gas producer ; next some 



engine details, notably ignition and carburatiom 



„ are shortly described ; finally, a chapter is devoted 



