156 



Mr. William Croohes 



[April 4, 



which I can set in action by touching a key, and the focus is then 

 drawn to the side of the glass tube (Fig. 17, 6). To show the first 

 action of the heat I have coated the tube with wax. I will put the 

 apparatus in front of the electric lantern (d), and throw a magnified 

 image of the tube on the screen. The coil is now at work, and the 

 focus of molecular rays is projected along the tube. I turn the 

 magnetism on, and draw the focus on the side of the glass. The 

 first thing you see is a small circular patch melted in the coating of 

 wax. The glass soon begins to disintegrate, and cracks are shooting 

 star wise fi*om the centre of heat. The glass is softening. Now the 

 atmospheric pressure forces it in, and now it melts. A hole (e) is 

 perforated in the middle, the air rushes in, and the experiment is at 

 an end. 



Instead of drawing the focus to the side of the glass with a 

 magnet, I will take another tube (Fig. 18), and allow the focus from 



Fig. 17. 



Fig. 18. 



rt\ 



M 



the cup-shaped negative pole (a) to play on a piece of platinum wire 

 (h) which is supported in the centre of the bulb. The platinum wire 

 not only gets white hot, but you can see sparks coming from it on all 

 sides, showing that it is actually melting. 



Here is another tube, but instead of platinum I have put in the 

 focus that beautiful alloy of platinum and iridium which Mr. Matthey 



