1amp/ u Sir Humphry I );i\ y ob-er\ ed that on introducing a piece ot' wire 

 u'au/.e into a tlame, it absorbs so much heat that combust ion docs not 

 proceed beyond it (the unburiit gase- which pass through it mav be 

 kindled on tin- other side). In accordance with this, the ilanie of the 

 l>avv lamp is surrounded with a thick glass (as shown in t he drawing), 

 and lias no comnitinicat ion whatever with the explosive* mixture except 

 through a wire ^au/.e which prevent- it igniting the mixtui'e of the 

 marsh-gas i-suin^ from the coal with air. In -ome place.-, particularly 

 in those districts \vhere petroleum is found as, for instance, near l>aku, 

 where a temple of the Indian tire-worshippers \vas built, and in 

 Ponnsvl vania, and other places marsh-gas in abundance issues from 

 the earth, and it is used, like coal gas. for the purpose- of lighting and 

 \varming. :u Fairly pure marsh gas ;<:> may be obtained by heating a 

 mixture of an acetate with an alkali. Acetic acid, < '., 1 1 ,( >.,. on being 

 heated is decomposed into marsh gas and carbonic anhydride, 

 C,H ,( ), = CH, + CO,. 



An alkali for instance. Nall() gives with acetic acid a salt, 

 (.".,! l;.Na(J.,, and on decomposition \\'ith excels of alkali, this retains 

 carbonic anhydride, and forms a carbonate, Xa ,( '< ).,. and marsh gas 

 is ft >rnied. 



C 2 H ;i NaO,-f NalK )=Na._,CO ;i + CH , 



Marsh o- as i- difficult to liijtiefv ; it is .almost insoluble in water, 

 and is without taste or smell. The most important point in connection 

 with it- chemical reaction.- is that it does not combine directlv with 



" Tin' Davy lamp is used fur li-htin- mill and 

 .iilu-i- niiii.'s where cninlui-.til.lr ..MS is luund. 'I'hr 

 wii-k i.f tin- lamp is I-J:I-I.^IM| in a thick -la 

 cylin.l.T. which is tinnly ln-l<l in a metallic hol.l.-r. 

 ( )\ el' ! lii- a metallic c\ limler and the u ire 'jaii/.e are 

 [ihiceil. The |n-i)duct- <>l ci utihu-t i< in jia thnni^li 

 the ;jMu/e. and the air enters thniiiuh the -pace 

 I iet ween tin 1 ry HlldiT ;ll)i| the \\ 1 1 i - i u . c. TM ell -lire 

 greater >at'et\ the lamp caninit lie i ipmcd \\ it limit. 



. \ 1 1 1 1 ;j II i - 1 1 1 1 1 L' the 1 1 a 1 II i . 



"' In I'enn-ylvauia il.e\,inl the A ll.-jha n y inoini- 

 tain-i many of the -hall-, -mils I'm 1 petroleum only 

 emitted LM-. lui! many useful application- tor it, 

 \\ere found, and il was ci.ndiicteil in metallic pijes 

 to work-, hundred- of mile- di-tant , principally for 

 i ne! a I 1 1 1 I'L 1 ica 1 | 'H I pi ise-. 



'' Ilie plll'e-t L'a- 1- prepared h\ I] 1 i X i 1 1 '_' the 



i 1 1 11 id ii list a nee called /.i nc methyl, /in < 'H-ij, wi til 

 \\-.\\i r. \\ hen t he ftillnw ill'' read i,.n (icclll's : 



