38 Transactions of the 



MEETING, June 2, 1871. 

 The Peesident in the Chair. 



The third meeting for the term was held on 2d June. Fifty- 

 four members and visitors were present. 



J. G. Gkenfell, Esq., read an interesting paper on 'The Geo- 

 logical Section at Portishead,' and he exhibited diagrams of the 

 strata, together with several specimens of the rocks and fossils 

 collected by the members of the Section. 



C. T. Blanshard (who was assisted in his experiments by 

 J. P. M. H. Stone) then read the following paper on 



GUN COTTON. 



I. Before I say anything about gun-cotton itself, I will shortly 

 go through the principle upon which the explosive property, whicli 

 it and bodies like it possess, depends. Nearly all the compounds 

 of nitrogen are unstable, or in other words, readily split up into 

 the elements from which they were originally composed ; M'e see 

 examples of this readiness of such compounds to decompose, in 

 decaying animal matter, which always contains nitrogen — in 

 those dangerously explosive substances formed by the union of 

 nitrogen with the so-called ' halogens,' bromine, iodine, and 

 'particularly the gaseous chlorine. In these three cases the 

 element nitrogen is so very loosely bound, so to speak, to tlje 

 halogen elements, that the slightest increase of temperature, or 

 even mere friction, is sufficient to make them fly asunder. Again, 

 other instances of the feeble affinity that nitrogen has for other 

 bodies, are the nitrates, and products obtained from them, all of 

 which contain oxygen and nitrogen in combination. You know 

 that when nitric acid is distilled (by acting on a nitrate with 

 sulphuric acid), red fumes of lower oxides of nitrogen come over 

 with it ; in fact, nitric acid cannot even be raised to its boiling 

 point without partial decomposition. As to the products 

 formed by the action of nitric acid on organic substances, or 

 compounds of carbon, which have been termed ' nitro -substitution 

 products ' (with which we have more particularly to do this even- 

 ing), they all contain the group of atoms, NO2, in various pro- 

 portions. Such a group of atoms as this, which enters into 

 combination with bodies, expelling from them a certain amount 

 of hydrogen, or it may be some other element, and taking the 

 place of the expelled element, is called a compound radicle ; thus 

 the compound radicle NOo, that takes the place of the hydrogen 



