116 Tlw Biyhf Ron. Sir John Macdonald [April 18, 



vigorously. That is to induce suction and compression to get their 

 engine to start. There was a driver in Glasgow busy turning his 

 handle, as a working man came up, who was a great connoisseur in 

 music. He stood for a moment, put his hand in his pocket, and took 

 out a penny. After watching a few turns, he said, " Man, have ye 

 no forgotten to put a barrel in ? " Presently there was a loud rum — 

 rum — rum — rum — suggestive of the beginning of the overture to 

 ' William Tell.' But no music followed upon that, and the man 

 remarked, " I think I'll just keep my penny till ye got her inside 

 right." 



The second question was, why the piston when forced up did 

 not stay jammed at the end of the cylinder. It would do so, but for 

 the use of a fly-wheel. I asked one of my lady friends the other 

 day if she knew what a fly-wheel was. She thought it had something 

 to do with Santos Dumont ; she evidently knew nothing about it. 

 The fly-wheel is based upon a very simple principle, that if you are 

 going to move anything, you cannot move it without putting some 

 energy into it. If a ball is thrown along the ground it rolls until 

 the energy imparted to it is exhausted, and it comes to a rest. A 

 light ball cannot go far — a ping-pong ball thrown would not hurt a 

 lady, but a golf ball driven by a club, or a cricket ball thrown by 

 hand or driven by a bat, might hurt severely. Here are two wheels 

 of the same size on one axle [model exhibited], and although I set 

 them spinning together, so far as I can honestly do it putting the 

 same amount of force on to both wheels, you notice that one has 

 stopped while the other is still revolving. The only difference 

 between them is that one has a tyre upon it and the other has not. 

 The one with the tyre is of course a little heavier, and therefore takes 

 more force out of my hand than the other to start it at the same 

 speed, and so it runs on longer. That is a simple illustration of the 

 fly-wheel, and here is the simplest and perhaps the oldest of all 

 illustrations of the fly-wheel — a spinning-wheel [model exhibited]. 

 A spinning-wheel is always made with a heavy outside rim, which 

 ensures equable motion, and it will run when the hand has to be re- 

 moved to attend to the thread. That is the principle of tlie fly-wheel. 

 Here is a model of one of these spirit engines with a heavy fly-wheel ; 

 when the fly-wheel is first turned round, the energy taken up by it 

 keeps the piston moving, causing it, through its crank, to change its 

 direction instead of being jammed against the end of the cylinder, 

 and so making the piston continue to move. 



The next point is, how is the explosion obtained ? 



There are two modes by which we fire our mixture in the motor 

 car. One is by means of a small platinum tube which goes through the 

 side of tlie cylinder. This tube is inserted in the space in which the 

 mixture is being pressed at the end of the cylinder ; it is kept white 

 hot by a lamp outside, and as the compressed air and gas are driven 

 against it, it ignites them and the piston moves. A preferable mode, 

 in my opinion, and one that is used more frequently, is by elec- 



