478 Sir Henry Cimynghame [Feb. 19, 



Captain Desborough has experimented with a small gun in a larger 

 gallery, and from his experiments he and I have designed a gallery 

 10 feet long strewn with dust which we shall endeavour to ignite 

 for you at the conclusion of the lecture by means of a miniature 

 blown-out gunpowder shot. 



The dangers of coal-dust having been thus described, it has next 

 to be considered how they are to be avoided. Three different 

 methods have been proposed. 



The first is dusting and sweeping. The difficulty of this is that 

 it is impossible effectively to remove the dust by means of brooms 

 and such like implements, for a very little dust is enough to cause an 

 explosion. 



A vacuum cleaner has been used in some places with a certain 

 measure of success. 



The most effective method is by means of hose and sprays to wet 

 any portions of the dusty main roads. 



The disadvantages of this plan are that in many places water 

 causes the coal to disintegrate and the roof and sides to fall, and is 

 therefore dangerous. 



A very damp mine is, moveover, not so healthy as a dry one. 



Another plan is to have zones of wet in the roadways. For it is 

 believed that explosions of dust can be stopped if they meet a wet 

 place, and in very many cases it has been observed that explosions 

 stopped at wet places. 



In order to see whether these zones are effective, the Associated 

 Coalowners of Great Britain have, with very proper public spirit, 

 built a testing gallery. This gallery is :^)61 yards long and 7 feet 

 6 inches in diameter. It is made of old boilers bolted together. 

 It has been designed and is under the care of ^Ir. (larforth, Past- 

 President of the Coal Owners' Association, and one of our most 

 skilful mining engineers. He has been good enough to have pre- 

 pared for us a model of the gallery, which is in front of the lecture 

 table. 



[Model.] 



He has also sent me some slides. 



[Photographs,] 



The explosions are created by means of blown-out shots of gun- 

 powder, the tubes being fitted with props like the gallery of a mine, 

 and liberally sprinkled with dry inflammable dust. 



It is premature to say what results will be obtained. But, so far 

 as we have gone, it appears probable that zones will be effective, and 

 it seems that if stone dust is mixed with the coal the force of the 

 explosion is much modified. 



There is one precaution which it is always desirable to take if 



