712 TRANSACTIONS OF SECTION G. 



at an assigned crank-angle can be accurately measured with a platinum 

 thermometer. Thus all the data are observed from which the weight of air 

 drawn through the orifice per cycle can be computed. Indicator diagrams were 

 taken with an optical indicator giving accurate results. Every indicator-card 

 was calibrated for pressure in situ. The peculiarity of the method is that a rela- 

 tively small orifice is used— so small, in fact, that the difference of pressure on 

 the two sides of it is equivalent to about one foot of water under normal con- 

 ditions of running. This difference of pressure can then be measured by means 

 of a U-tube, and small variations of head are easily observed. Numerous 

 experiments established the fact that the coefficients of the orifices tried were 

 practically constant and equal to 0-6. The gas-supply can be measured through 

 an orifice in the same way. Hence the mixture of air and gas passing into the 

 cylinder can be obtained from two readings, with suitable corrections for 

 density, at any time during the run. The orifices, in combination with their 

 U-tubes, become rate measurers, the one giving the rate at which air is supplied 

 to the engine, and the other the rate at which gas is supplied. 



3. The Laws of Electro-Mechanics. 1 

 By Professor S. P. Thompson, F.B.S. 



4. The Testing of Heat-insulating Materials. 2 By Frederick Bacon. 



5. A New Method of producing High-tension Electrical Discharges. 3 

 By Professor E. Wilson and W. H. Wilson. 



According to this method energy is taken from an alternating or continuous 

 current source and stored in a magnetic field by an inductance; it is then per- 

 mitted to surge into a condenser, which forms with the inductance a low fre- 

 quency oscillatory circuit. When the energy is accumulated in the condenser 

 the latter is mechanically bridged across the primary winding of an induction 

 coil, with which it forms a high frequency oscillatory circuit. The energy is 

 then transmitted by the secondary winding of the induction coil to the work 

 circuit, and can be of an oscillatory or uni-directional character according to the 

 purpose in view. The apparatus is light, efficient, and cheap, and is especially 

 suitable for radio-telegraphy, x-ray, ignition, and other work in which high 

 tension electricity is employed. 



WEDNESDAY, SEPTEMBER 7. 

 The following Papers were read : — 



1. Gravity Self-raising Boilers.* By R. W. Weekes. 



2. The Mechanical Hysteresis of Rubber:' By Professor Alfred Schwartz. 



The increasing importance of the applications of rubber in the Arts calls for 

 carefully standardised tests of the properties of this material. 



The physical properties of rubber of which use is made in industrial work are 

 its elasticity, compressibility, extensibility, tenacity, flexibility, adhesiveness, 



1 Published in abstract in Engineering, September 16, 1910. 



2 Published in Engineering, September 16, 1910. 



3 Published in the Electrician, September 9, 1910. 

 * Published in Engineering, October 14, 1910. 



5 Published in the Electrical Review, September 23, 1910, and in Engineering, 

 September 16, 1910. 



