Decembee 25, 1908] 



SCIENCE 



903 



unstable in the presence of the air and 

 water, even at the ordinary temperatures 

 at which organic synthesis takes place. On 

 reaching the surface of the earth, these 

 compounds would therefore have been no 

 longer stable, but must have sought new 

 relations. The transfer from the one state 

 to the other may well have been accom- 

 panied by combinations not likely, or at 

 least less likely, to arise under modern con- 

 ditions of greater stability. 



As already noted, a carbide of iron, 

 nickel and cobalt is found in meteorites. 

 The conditions attending the formation and 

 infall of planetesimals encourage the belief 

 that a wide range of carbides, and probably 

 also of nitrides, may have existed among 

 the accessions to the growing earth. But 

 whether the amount of such material was 

 large or small, it is clear that, as it was 

 borne to the earth in the divided state of 

 planetesimals, its measure of contact with 

 the moisture of the surface was exception- 

 ally large and hence the suggestive reac- 

 tions which follow under these conditions 

 should have been large in proportion to the 

 amount of carbides and nitrides present. 

 Even with cold water, the carbides of 

 barium, strontium and calcium give rise to 

 acetylene, while the carbides of aluminium 

 and beryllium generate methane. Under 

 the same conditions, uranium carbide gives 

 rise to a gaseous mixture of methane, 

 hydrogen and ethylene, and in addition to 

 this generates considerable quantities of 

 both liquid and solid hydrocarbons.^ "While 

 nitrides are not known to furnish directly 

 such a varied assortment of gases, they may 

 readily give rise to ammonia gas under 

 various conditions. Iron nitride, heated to 

 200° C. in the presence of hydrogen sul- 

 phide, yields iron sulphide, a sulphide of 



'Moissan, Proe. Roy. 8oc., Vol. 60 (1897), pp. 

 156-60. 



ammonium, and free hydrogen (2Fe2N -j- 

 6H,S = 4FeS + 2NH,HS + HJ." 



It is impossible to follow the remoter 

 reactions which might spring from these 

 various first products of the carbides and 

 nitrides by further interaction, but it is to 

 be noted that all the new products, if 

 closely associated, as the conditions of the 

 case imply, were liable to meet one another 

 while in the state of nascent activity, or in 

 such stimulated activity as may attend pre- 

 vious activities, however this may be inter- 

 preted. Reaction might also have been 

 aided by the catalytic relations into which 

 these products came in their intimate asso- 

 ciation with the debris of the surface, with 

 one another and with the new accessions 

 added constantly to the earth's surface. 



As already noted, the superficial portion 

 of the growing earth is supposed to have 

 been a loose, incoherent aggregate of highly 

 fragmental planetesimal matter, and this 

 was subject to weathering and various 

 forms of comminution. The resulting 

 porosity may have led to the condensation 

 of much of the gaseous matter within its 

 capillary and subcapillary pores, as soils 

 are known to do at the present time. The 

 graphite and amorphous carbon may have 

 acted somewhat after the analogy of char- 

 coal which is well known to absorb certain 

 gases to a phenomenal extent. Various 

 porous substances, including earths, possess 

 this property of gas-condensation in appre- 

 ciable degrees. Not a few metals also pos- 

 sess, irrespective of porosity, certain occlu- 

 sive affinities or selective powers of absorp- 

 tion for certain gases, as palladium and 

 platinum for hydrogen, etc. While the 

 efficiency of charcoal is clearly due in large 

 part to its extreme porosity, it is doubtless 

 due in part also to the substance itself, for 

 coal manifests a somewhat similar property. 

 Fresh coal rapidly absorbs oxygen from the- 

 " Fowler, Jour. Chem. Soc, Vol. 79, p. 297. 



