298 LIGHTING BY GAS. 



stances ; but it is not uncommon to find a quantity of il- 

 luminating gas sufficient to fill a room thirty feet square 

 and ten feet high so closely compressed in the coal con- 

 taining it, that if, while it was in that state, it could be 

 separated from the other constituents of the coal, it would 

 form a solid block which a man could easily lift. 



Thus, as Lawrence said, bringing the gas on board the 

 vessel packed in paraffine or in coal is altogether a more 

 convenient mode than to attempt to bring it in pure, in its 

 natural form and of its natural bulk, as gas. In the form 

 of paraffine it is much more expensive, in the first instance, 

 than as one of the constituents of coal, but then it is much 

 more easily extracted, or, perhaps, it would be Better to 

 say, developed, from that substance than from coal ; for, 

 in the case of paraffine, or wax, or tallow, or any other such 

 substance, all that is necessary is to have a wick passing 

 up through it and set on fire, and the process of melting 

 successive portions of the substance, and converting them 

 into an illuminating gas, goes on of itself, without any ap- 

 paratus or machinery whatever. 



Whereas, on the other hand, although people might ob- 

 tain the necessary supply of gas in coal cheaper than in 

 any of those other forms, there would be required a com- 

 plicated, and expensive, and bulky, and even somewhat 

 dangerous apparatus to distill it. There would have to be 

 a furnace to heat the coal, and tight iron 'retorts to contain 

 it so as to prevent the gas from being burned in the fur- 

 nace as fast as it was produced, and a reservoir to store it, 

 and pipes to convey it to the different parts of the vessel 

 ivhere it might be required, all of which would involve 

 much trouble and expense. 



" That would not do at all," said John, when Lawrence 

 explained these things to him. 



"Especially," he added, after thinking a moment, "in 



