ill 



088 



KEPORT — 1 884. 



Iv, 



'ft M !■ 



A table was exhibited which showed the comparative chamcters, as to percent- 

 npe of nitrogen and carbon, of exliaustcd arable soils, of r.'wly laid-down pa=iturp 

 and of old pasture soils, at llotbamsted ; also of some other old arable soils hi 

 Great Britain ; of some Illinois and Manitoba prairie soils ; and lastly, of some vorv- 

 rich Russian soils. From these results there could lie no doubt that a charaoteristic 

 of a ri(?h -virprin soil, or of a permanent pasture surface soil, was a relatively lii'fli 

 percentage of nitrogen and carbon. On the other hand, soils which have long lipon 

 under arable culture are much poorer in these respects ; whilst arable soils luuhr 

 conditions of known agricultural exhaustion show a very low percentage of nitrm'en 

 and carbon, and a low relation of carbon to nitrogen. 



In conclusion, the authors said it had been maintained by some that a soil was 

 a laboratory and not a mine ; but not only the facts adduced })y them in this and 

 former papers, but the iiistory of nirriculture throughout tlie world, so far as it was 

 linown, clearly showed that a fertile soil was one wliicli liad accumulated within it 

 tlie residue of ages of previous A'egetation ; and that it became infertile as this 

 residue was exhausted. 



5. On tlie Velocity of Exjjlosions in Gases. JBi/ H. B. Dixon, M.A. 



MM. Berthelot and Vieille have found that in hydrogen and oxygen, ethane 

 and oxygen, and many other mixtures of gases, the ' explosive wave ' is propa- 

 gated with a velocity closely a])proximating to the mean velocity of transhitinr. 

 of the gaseous products of combustion, calculated en the assumption that al! thi- 

 heat of the reaction is retained for tlie moment in the products formed, Thu? 

 the mean of a number of determhiations with electrolytic gas gave a velocity of 

 1^,810 metres per second ; the calculated mean velocity of the steam molt'ciile 

 formed being y,H;}i metres per second. 53ut with carbonic oxide, exploded eitlier 

 with oxygen or nitrous oxide, the velocity of explosion was much less than tlie 

 calculated velocity. The author has shown that steam is necessary for the burii- 

 ing of carbonic oxide, both with oxygen and nitrous oxide, and that as the pro- 

 portion of steam is increased the rate of iuHammation is also increased. 



Preliminary experiments made in a lead tube, Ai") metres long and 18 mni. 

 internal diameter, entirely confirmed M.M. 13erthelot and Vieille's experiments with 

 electrolytic gas. The velocity of the explosive wave was found to be 2,817 metrw 

 per second, as the mean of several closely concordant determinations at 10" 0. 



"With a nearly dry mixture of carbonic oxide and oxygen, the explosive wave 

 wap not established until the Hame had traversed a distance of 700 mm. from 

 the firing point. The explosive wave was found to have a velocity of rather over 

 ],oOO metres per second. After the explosion a tine layer of carbon was found to 

 cover the inside of the tube, showing that at the enormous temperature reached ia 

 the explosive wave, carbonic oxide is decomposed into its constituents. 



6. On the Colour of Chemical Compounds.^ 

 1)1/ Professor Tnos, Carnelli- v, D.Sc. 



The colour of chemical compounds is conditioned by at least three circum- 

 stances, viz. : — (1) Temperature (Ackroyd), (2) the quantity of tlie electronega- 

 tive element present in a binary compound (Ackroyd), (.']) the atomic weights of 

 the constituent elements of the compound (Carnelley),and that in sucli away that 

 the cidour passes or tends to pass through the following chromatic scale : — 



White or colourless 

 Violet 



Indigo 

 Blue 



Green 



Yellow 



Orange 

 Bed 



Brown 

 Black 



either by (1) rise of temperature, or (2) increase of the quantity of the electra- 

 negative element in a binary compound, or (.'^) with iixrease of the atomic irei^lits 

 of the elements A, B, (', kc, in the compounds A ,^ !{•;, B^ llj,, C^ 11^, &c., in 



> Phil. IL'aff. (5), 18, 130. 



