-138 Proceedings of the Royal Society of Edinburgh. 



paracyanogen once formed cannot be again converted into cyanogen. 

 Professor Johnston supposed the contrary, because he obtained cyano- 

 gen gas by exposing paracyanogen to a strong heat. But the author 

 found that this arose from the latter having retained some cyanogen 

 by absorption, that after the absorbed gas is removed heat subse- 

 quently expels nitrogen only, and that the same result is obtained 

 from the first by using pure paracyanogen, prepared by dissolving the 

 impure substance in concentrated sulphuric acid, and separating it in 

 a state of purity by leaving the acid exposed to the air so as to attract 

 humidity. 



To these facts the author added some views as to the composition 

 of cyanogen and paracyanogen, and their relation to one another. In 

 order to account for the exceeding difference in properties prevailing 

 between these two bodies, which appear nevertheless to consist of 

 the same relative proportions of the same elements, — chemists gene- 

 rally consider tho former to consist of one equivalent of carbon and 

 two of nitrogen (N C 2 ) and the latter of two equivalents of the for- 

 mer and four of the latter (N 2 O). But the author endeavours to 

 shew that the true constitution of paracyanogen is that in which it is 

 regarded as a compound of two equivalents of cyanogen, that is, of 

 two " equal and similar atoms" of tho same body. 



In conclusion, the author proceeded ta> apply these views to the 

 constitution of the simple or elementary bodies ; and endeavoured to 

 shew that there is nothing unreasonable in the supposition, that, — as 

 chemists arc now acquainted with various instances of compound 

 bodies which have widely different forms, different physical proper- 

 ties in general, and different chemical relations, although agreeing 

 exactly in their intimate constitution, — so, in like manner, some of 

 those bodies, which are at present accounted elements distinct from 

 one another, may really be isomeric, that is, different forms of one 

 common element. And he stated that ho hoped to be able to adduce 

 experimental evidence of such being the fact with two of the most 

 familiar of the elements, which until now have been considered wholly 

 distinct." 



3. A notice was communicated by Mr Mylne from Joseph 

 Atkinson, Esq. of results obtained with Rain-Gauges of 

 different forms. 



