18 Mr. G. Gore on a new Gas-Furnace for 



this test is liable to fallacy if employed when the gas is just 

 lighted, because the coldness of the parts makes the flame much 

 whiter than it otherwise would be ; it is also fallacious when the 

 crucible is very hot, the flame appearing whiter than it really is ; 

 it is, however, of great assistance at intermediate temperatures. 

 A. rough deposit upon the outer edge of the crucible indicates an 

 excess of gas ; the deposit is carbon. 



Less gas is required with a crucible in the furnace than with- 

 out one ; also less is necessary when the small hole at the top of 

 the furnace is open than when it is closed; and less is also 

 required when the furnace is cold than after it has been lighted 

 some time, because the draught gradually increases and draws in 

 more air. After having accurately adjusted the gas, no further 

 attention to the furnace is requisite. 



Having once found the proper adjustment of gas under certain 

 known circumstances, it is well to notice the position of the 

 index N, in order to be able at once to adjust it to the right point 

 on other occasions. Under ordinary circumstances, during day- 

 light I have found it best to set the gas nearly fully on at first, 

 and fully on at about five minutes afterwards when the draught 

 has become more powerful ; but during twilight, when the supply 

 of gas from the gas-works is more free, I have set the index- 

 pointer at the numbers 2 \ or 3. The gas should be supplied by 

 a pipe of not less than § ths of an inch bore, with a main pipe of 

 half an inch ; but all depends upon the pressure of gas at the 

 particular locality, which is very variable. The consumption of 

 gas varies from 30 to 40 cubic feet per hour, the cost of which is 

 about twopence. 



The top of the chimney should be placed in a position where 

 the products of combustion can pass freely away ; if it is placed 

 in an opening or pipe leading to another chimney, care must be 

 taken not to have the draught too powerful, otherwise the heat 

 will be drawn more into the chimney, and the supply of gas in 

 the daytime may be found rather deficient. The furnace will 

 act satisfactorily, though less powerfully, with the chimney stand- 

 ing in an open room without any special outlet for the products 

 of combustion, provided the full height (6 feet) of chimney is 

 employed; under other circumstances I have generally used a 

 chimney 4J or 5 feet in height. 



This furnace will readily melt half a pound of copper or six 

 ounces of cast iron. I have melted those quantities in it : it will 

 melt as large a quantity of those substances as the largest-sized 

 crucible that can be introduced into it will contain, sufficient 

 space being allowed around the crucible for draught. It requires 

 from 20 to 30 minutes to acquire its highest temperature ; and 

 then the entrance part of the chimney exhibits a faint red heat in day- 



