198 THE FIRE-DAMP'S FAMILY CIECLE. 



depend on the dimensions of the mine. For small mines 

 Mr. Gurney believed that one light would suffice; but he 

 was confident that if seven lights of the first order were 

 placed in the focus of seven true twelve-inch parabolas, and 

 arranged within a circle of three feet diameter, one of the 

 largest mines might be effectually lighted in every gallery. 



Many of the difficulties (theoretical ones at least) which 

 oppose themselves to the adoption of Mr. Gurney's system 

 are obvious. Supposing it conceded, to set out with, that 

 artificial light can be procured of sufficient power to bear 

 the numerous angular deflections which would be necessary 

 in practice, a clear way is obviously necessary to give it 

 transmission. It cannot, however brilliant, travel from one 

 end to the other of a gallery, if the gallery be obstructed 

 with opaque matters, whether stationary or in motion. 



The galleries of a coal-mine are its high roads, its traffic 

 ways, for man and beast. Every here and there across the 

 road there is a doorway provided with an accurately shutting 

 door, opened to let the traffic pass by, and then carefully shut 

 again. The safety of every breathing thing within the mine 

 depends on these doors. They are the very doors and door- 

 ways of life and death, inasmuch as they are subservient to 

 and regulate ventilation. 



Now light, even of the first order, and darted from a 



o 7 J 



parabolic reflector, cannot get through a wooden door. < Put 

 glass panes in the door,' argued Mr. Gurney. Let us con- 

 ceive it done. Again, it happens that the hands and the eyes 

 of a human individual are situated in the same bodily aspect. 

 A miner faces his work; Mr. Gurney's light would strike 

 a posteriori, and treat the miner to a magnificent shadow. 

 Again, mine-inspectors ask how the horses employed below 

 would like to come unawares upon one of Mr. Gurney's arti- 

 ficial sunbeams darting into their eyes ? 



These objections are not mine. They have been urged 

 before parliamentary committees, and are to be found in the 



