384 SECTIONAL TRANSACTIONS.— G. 



offensive and defensive characteristics of a war-vessel, and any one of ibeie 

 characteristics, such, for example, as economy in fuel, has on occasion to give 

 way to other more important features. 



The details of naval practice in respect to the burning of fuel are described, 

 together with some of the results obtained, the types of machinery fitted, and 

 the measures adopted to attain and maintain fuel economy on service. 



(d) Mr. A. Spyee. 



The works of the National Radiator Co. were visited. 



Tuesday, September 12. 



6. Mr. J. Richardson. — The Propelling Machinery of the Cargo- 



Carrier of the Future. 



7, Joint Discussion with Section L on The Effect of Reformed 



Methods in Teaching Mathematics. (See p. 406.) 



The works of the British Oil and Cake Mills, Ltd., were visited. 



Wednesday, September 13. 



8. Dr. E. O. Turner. — Electrical Ignition Apparatus for Internal 



Coinbusiion Engines. 



(1) General. — The requirements to be fulfilled by ignition apparatus were 

 stated ; the importance of sparking being continuous with high conductivity 

 secondary branch circuit was pointed out, ond the term ' utility ' explained. 

 The effect of varying cylinder compression due to varying speed and firing angle 

 was considered, and in order to provide a means of comparing ignition units of 

 different design expressions were suggested as figures of merit for induction coils 

 and magnetos respectively. The use of tungsten and iridio-platinum alloys 

 for contact-breakers was referred to, and the question of the time of duration 

 of contact at high speed and its influence on functioning was examined. 



(2) Ignition hy Inducfinn Coil. — The magnetic circuit, primary and secondary 

 windings, and operation under the conditions obtaining in practice were dis- 

 cussed, and curves showing the results of experiments on induction coils designed 

 for use with automobiles and with high-compression stationary gas-engines were 

 illustrated. 



(,3) Ignition hij Magneto. — The magneto was considered in two aspects — as a 

 constant flux alternator on short circuit for the first part of each cycle (until 

 the contacts open), and thereafter as an induction coil breaking the current 

 just established. Expressions for the equivalent magnetic circuit and the 

 'spark flux ' were deduced; the latter was shown to be dependent on the short- 

 circuit current and the equivalent permeance of the magneto. Drawbacks of 

 the tungsten steel magnet magneto were pointed out, and the improvements made 

 possible by the substitution of cobalt steel magnets were referred to; typical 

 experimental curves supporting the conclusions arrived at were shown. 



9. Mr. C. E. Stromeyer. — Resolution of Compound Stresses. 



Stresses are always balanced ; the push and pull in a bar are the same at 

 both its ends. Forces, on the other hand, when acting on masses may be con- 

 sidered to be unbalanced. Nevertheless, in spite of this dissimilarity, the 

 process ofresolving stresses is based on the law of acceleration of masses! ' The 

 more straightforward procedure would be to deal with the problem direct. 

 Definition ; A vesultant force produces tlie same acceleration in ii. mass as is 



