B6 Analyses of Books, [Jaw. 



diminished to4, whicli were pure oxygen. Hence three volumes 

 of mixture had been detonated, of which nearly 0-34 was vapour 

 of the substance, and 2-65 oxygen. The carbonic acid amounted 

 to 2'1 volumes, and must have consumed an equal bulk of oxy- 

 gen gas ; so that 0-65 remain as the quantity of oxygen which 

 has combined with the hydrogen to form water, and which with 

 the 0'34 of vapour nearly make the diminution of 0*9. 



It will be seen at once that the oxygen required for the carbon 

 is four times that for the hydrogen ; and that the whole state- 

 ment is but little different from the following theoretical one, 

 deduced partly from the former experiments. 1 volume of 

 vapour requires 7'5 volumes of oxygen for its combustion ; 6 of 

 the latter combine with carbon to form 6 of carbonic acid, and 

 the 1*3 remaining combine with hydrogen to form water. The 

 hydrogen present, therefore, in this compound is equivalent to 

 3 volumes, though condensed into one volume in union with the 

 carbon ; and of the latter elements there are present six propor- 

 tionals, or 36 by weight. A volume, therefore, of the substance 

 in vapour contains 



Carbon 6 x 6 = 36 



Hydrogen 1x3= 3 



~^ 



and its weight or specific gravity will be 39, hydrogen being 1. 

 Other experiments of the same kind gave results according with 

 these. 



{To lie continued,) 



Article X. 



Analyses of Books. 



Comiderutions on Volcanos, the probable Causes of their Phceno' 

 metia, the Laws which determine their March, the Disposition 

 of their Froducts, and their Connexion with the present State 

 and past tiistury of the Globe. By G. Poulett Scrope, Esq. 

 Sec. GS. Ph.llips, 1825. 



Th e author commences this work with a descriptive account of 

 the phienomena of volcanos, remarking on their numberand disper- 

 sion over the globe's surface, their division into subaeriul and 

 subaqueous vents, and the various conditions in which they at 

 tiuies appear, and which he classes as. Phases, 1. Of permanent 

 eruption ; 2. Of moderate activity ; and 3. Of prolonged inter- 

 mitteiices. Examples are given of these several phases, and a 

 detailed description of their most ordinary characteristics. 



