Jan. 13, 1888.] 



SCIENTIFIC NEWS. 



33 



HOUSEHOLD EXPERIMENTS ON HEAT. 



THE handle of a flat-iron, though protected from the 

 fire by the flat smoothing surface, soon becomes 

 too hot to be touched by the fingers, the reason for 

 this being that the heat taken up by the flat surface of 

 the iron is conducted through the metal to the handle. 

 In the case of a soldering iron the metallic portion is 

 mounted in a wooden handle, which can be touched with 

 impunity even when the tool is so hot that the part of 

 the wood in contact with the metal is actually scorching. 

 Why should there be this difference between the beha- 

 viour of the handle of the iron and the handle of the 

 soldering tool ? The answer is simply that the iron is a 

 better conductor of heat than wood. Another very 

 simple method of showing the difference between a good 

 and a bad conductor is shown in our illustration, taken 

 from a recent number of Za Nature. A penholder with a 

 metallic barrel is taken, and a piece of paper is bound 



THE PETROLEUM GAS CANDLE. 



'T'HIS ingenious and safe lamp, burning petroleum 

 vapour, was invented by Mr. Chandor, whose name 

 is well known in connection with the early history of the 

 American petroleum industry. 



The lamp has the form of a bedroom candlestick, the 

 lower part forming the reservoir for the oil. This has a 

 peculiar construction ; in the centre is a hollow metal 

 cylinder soldered at the top to the outside part of the 

 reservoir, which extends nearly to the bottom of the oil 

 receptacle, leaving only a space Q, about the thirty- 

 second of an inch high, between them. The reservoir is 

 filled by pouring the oil into this cyhnder, the displaced 

 air finding its exit by the tube C, which is protected 

 from a light by the match-box plate D. 



Experiment to Illustrate the Conduction of Heat. 



Chandor's Petroleum Gas Candle. 



round it so as to be partly over the wood and partly over 

 "the metal. If this be then cautiously heated over a 

 •spirit lamp, the paper round the wood will be scorched, 

 while that round the barrel will not be discoloured. The 

 metallic barrel conducts the heat away so quickly that 

 the temperature of the paper over it does not rise 

 enough for it to be scorched. 



The action of the gauze in the safety lamp used by 

 ■miners is somewhat analogous to the eifect of the metallic 

 barrel, the temperature of any gaseous mixture burning 

 inside the lamp being reduced by the conduction below 

 the igniting point of the mixture, so that until the gauze 

 itself becomes red hot the miner is safe. Again, in tea 

 and coffee-pots the non-conducting property of wood or 

 ivory is taken advantage of by the insertion of small 

 plates of these or other non-conducting materials 

 between the pot and the handle, and even in some cases 

 by making the handles themselves of bad conductors. 



■•-3»t^^5tf^ • 



Vine Fungus. — An additional pest, Coniothyrium 

 diplodieUa,\is.s attacked the vines in the south of France, 

 causing the grapes to shrivel and dry up. The enemy is 

 a fungus. 



The burner is composed of two portions ; the inner part 

 screws into the top of the cylinder, and carries the wick 

 tube H and ratchet O for moving the wick. The wick tube 

 is surrounded by an outer tube P, communicating with the 

 air by an opening at E. To prevent any risk of explo- 

 sion, the tube G passing from the cylinder to near the 

 burner is provided, so that should the oil by any chance 

 become warmed its vapour is led away to the flame. 



Fitting very tightly to the burner, so as to make a 

 nearly air-tight joint, is the outer burner, consisting of an 

 inner cylinder of wire gauze K, surrounded by a per- 

 forated cylinder L, which is bent over at the top, forming 

 the burner B. An opalescent tube M is fitted outside 

 this cylinder, giving to the whole the appearance of a 

 candle. To protect the flame from currents of air it is 

 surrounded by a glass shade S. 



In using this lamp the external burner is removed and 

 the little wick lighted, which then burns with a small 

 flame like that given by a benzoline lamp. When the 

 outer burner is placed over this, a stream of smoke issues 

 from the opening at B, as the supply of air passing through 

 the small aperture E is insufficient for the complete com- 

 bustion of the oil. On applying a light, the vapour 

 ignites, and, as soon as the shade becomes warm, burns 



