COLLIERY EXPLOSIONS. 
219 
namely, that in order to allow of combustion a certain tempera- 
ture is necessary. Hence it is that combustion will not pass 
down small tubes, as the temperature is not maintained by 
reason of the cooling effect of the tubes. In the first lamps, air 
was admitted through small tubes at the bottom of the lamp, 
and the products of combustion, after passing up a glass chimney, 
passed out through similar tubes at the top. If air contaminated 
with explosive gas passed into the lamp, it might ignite within, 
but before the flame could pass to the outside air it must pass 
through the exit tubes, and in so doing it would be extinguished 
owing to the lowering of the temperature. Later on. Sir 
Humphrey Davy added the gauze chimney to his lamp, but the 
principle is the same, the meshes of the gauze acting the part 
of the tubes. It is this lamp wfliich is known as ‘‘ the 
Davy.” 
It must not be concluded that safety lamps are perfect 
indeed, they must be very carefully handled. They require to 
be carried with care ; if swung about, the contact of the flame 
against the gauze makes it red-hot, and when this is the case, 
flame passes through the meshes, and the lamp becomes worse 
than useless. If there be a sudden rush of air, or too strong a 
current of air, the flame is blown against the gauze with a like 
result. The Stephenson lamp, which remains unaltered from 
the first, goes out in the presence of firedamp. 
After the invention of the safety lamp, colliery explosions 
became for a time less frequent, but of late they have multiplied 
again. I have no statistics before me to show the frequency of 
these catastrophes before safety lamp^ came into use ; probably 
they were more frequent than now, but the loss of life was 
not so great. This is to be explained by the underground 
workings being much less extensive than at the present time and 
consequently fewer men were employed. It is, however, a fact, 
I tbink, that our collieries are becoming yearly more dangerous 
