644 THE POPULAR SCIENCE MONTHLY. 



with that relating to the difficulty of combustion of the combined 

 vapors, I have used largely in these researches the mixture of chloro- 

 form and carbon bisulphide. The combined vapors produce also a 

 singularly good antiseptic atmosphere. 



Coal- Gas. — Common coal-gas is one of the most potent of nar- 

 cotizing gases. It is a compound of four gases, three of which are 

 excellent narcotics, and one a negative gas — forty-seven per cent of 

 hydrogen, forty-two of marsh-gas, three of heavy hydrocarbons, and 

 eight of carbonic oxide. All these gases are anaesthetic in their action : 

 marsh-gas is one of the best, and carbonic oxide is one of the quickest ; 

 but they are all explosive. 



For the lethal purpose, nothing could possibly surpass coal-gas. I 

 put it freely to the test, and found it was all that we could desire. In 

 an atmosphere containing twenty-five per cent of this gas, an animal 

 goes to sleep in from two to three minutes, and dies asleep as easily as 

 in any narcotic vapor or gas whatever. The gas is always at hand, 

 and for the present purpose is the cheapest and readiest of all. Under 

 such circumstances, it seems absurd to think of going any further for 

 a narcotic agent. And yet it is necessary, at all events, when a large 

 lethal chamber is wanted, on account of the danger from explosion. 

 All things considered, I was led to conclude that carbonic oxide was 

 the best narcotic agent to employ, combining it with chloroform or 

 carbon bisulphide, if that should prove necessary. Deciding on this 

 point, the next question was how to manufacture the carbonic oxide 

 so as to bring it into practical use on the easiest as well as the largest 

 scale. 



After making some unsatisfactory experiments, I luckily recalled 

 Mr. Clark's condensing-stove. This is a most ingenious invention. 

 The fumes proceeding from the combustion in the furnace first ascend 

 and then descend through two lateral columns, to escape by a tube 

 directed over a trough or saucer. A large quantity of water-vapor 

 is in this way condensed, and is collected at the base of the stove, 

 together with substances derived from the combustion, which are solu- 

 ble in water. Here, with a little modification, was what I wanted. 

 To adapt the stove to my purpose, I got Mr. Clark to make a charcoal 

 furnace over a gas-burner, so that, when the charcoal was laid in the 

 furnace, it could be instantly set alight by merely turning on and 

 lighting the gas, letting the flames of gas play through the charcoal. 

 Next I got him to make a large condensing cistern beneath the stove, 

 with an opening from it to convey the carbonic oxide by a tube into the 

 lethal chamber, and with a tap, by which the condensed fluid could be 

 drawn off. The arrangement answered straight away, if I may so say. 

 The immediate combustion of the charcoal by the gas yielded very 

 nearly the theoretical value of the product, carbonic oxide. The gas 

 was deprived of water by the condensation ; it was delivered over to 

 the chamber with a steadiness sufficient for all practical necessities ; 



