1 1 YI>I:O< ;i-;\ combines with oxv^'en in the proportion of t\vo volumes to 

 one. The composition ly volume of nitrous oxide is exaetlv similar 

 it is composed of two volumes of nitrogen and one volume of oxv^en. 

 P.v decomposing ammonia liv tlie action of ;in electric spark it is easv 

 to prove tli;it it contains one volume of nitrogen to three volumes of 

 hvdroLi'en. So, similarly, it is found, whenever ;t compound is decom- 

 posed and tlie volumes of the ibises proceeding from it are measured, 

 that tlie volumes of the ibises or vapours entering into combination 

 are in a verv simple proportion one to another \\"ith water, nitrous 

 oxide, t v<-.. this may be proved by direct observation, bui in themajoritv 

 if cases, and especially with substances which, although volatile that 

 is, capable of passing into a gaseous (or vaporous) state are liquid at 

 the ordinarv temperature, such a direct method of observation pre- 

 sents manv difficulties. Hut then, if the densities of the vapours and 

 erases lit- known, the same simplicitv in their ratio is shown bv calcula- 

 tion. The \olumeof a substance is proportional to its weight and 

 inverselv proport ional to its densitv. and therefore hy dividing the 

 amount liv weight of each substance entering into the com]>osition of 

 a compound li\ - its densitv in the gaseous or \aporous state we shall 

 olitain factors \\hich will be in the same proportion as the volumes of 

 the substances entering into the composition of the compound.' So. 



i If the v.> i-ht In' indii-iitci] l,y I'. tli.> density l>\ I >. iinil Ilir VohniH' hy \', tlini 



P KV. 

 I) 



,,-'-,- , dill; nil t hi' \ -ti'lll nf Illr cv |,]T i<.|| ; I'. I ). mid V. If I > 



. mi Irii'iil \ h in ( liiip. I. Nnli' '.' . Ilii- cnhic niciisurc \' 



' f he I .iki'll .1 :i Unit nl' Viilllllir t lu'li l\ I . I'.llt \\ ll;lli'\ iT it 

 mm ..!-. f.iki'ii. In MM , .-I ... | ,t .T. :i 1 1 1 r- .1 r 'I mil t, tin- hunk. (In- 



