often allowed no light, and sit in a hole cut in the side of the road near to the doors.  Upon their carefulness the safety of the mine in a great measure depends, as if they neglect to shut the door the current of air is changed.  I have been told that these boys are subject to accidents no less than the workers, for, sitting in the dark, and often alone for hours, they are very apt to go to sleep.  To ensure being awoke at the proper time, they frequently lie down on the line of rails under the rope, so that when the rope is started it may awake them by its motion, but at times so sound is their sleep, that it has failed to rouse them in time, and a train of coal waggons has passed over them, causing in most cases death.

The coal having been brought to the pit-mouth, it remains to be shown what becomes of this most valuable mineral, the consumption of which is now so large in all parts of the globe.  The next person employed in the trade is the sailor, to convey it to the market, and the collier vessels are a valuable navy to the country, proving quite a nursery of seamen for our royal marine service.  Newcastle, Sunderland, West Hartlepool, and a large number of other ports along our coast, have an immense amount of shipping employed exclusively in the coal trade—­no less than 5359 vessels carrying coal having entered the port of London alone in 1873, and the average annual quantity of coal exported abroad during the three years ending 1872 was 12,000,000 tons.

I will not now detain you longer on the subject of the extent and working of coal, lest I should tire your patience; but before concluding I should wish to give some account of the uses to which this most valuable product is applied.  The main use of coal, as we all know, is to produce heat, without which many a paterfamilias would grumble when the dinner-hour came and he had nothing hot to eat.  It not only, however, supplies heat, but the beauty of the processes for lighting up our houses is now mainly derived from coal.  The immense consumption of coal, among other things, is in the production of the vapour of water—­steam, by which our thousands of engines on sea and land are made to perform their various appointed tasks.  This production, formed of decayed vegetable matter, which in ages past nourished on the surface of the earth, as I have already shown, is again brought forth for our use, and is a testimony of the goodness and kindness of God in providing for our wants.  By its heat some 10,000 locomotive engines are propelled, and many hundreds of iron furnaces are kept in work, besides those for other purposes.  It moves the machinery of at least 3000 factories, 2500 steam vessels, besides numerous smaller craft, and I cannot tell how many forges and fires.  It aids in producing delicacies out of season in our hothouses.  It lights our houses and streets with gas, the cheapest and best of all lights—­London alone in this way spending about L50,000 a year.  It gives us oil and tar to lubricate machinery and preserve timber and iron; and last, not least, by the aid of chemistry it is made to produce many beautiful dyes, such as magenta and mauve, and also, in the same way, gives perfumes resembling cloves, almonds, and spices.