Carbon^ Silicon, and Nitrogen. 11 



elements may be transmuted into gold, which has the highest 

 atomic weight ; for, in this respect, Dr Brown's views are 

 strictly in accordance with those of the alchymists ; but gold 

 can be changed into none of them, and, if it suffer transmu- 

 tation, must pass into some unknown new body possessing a 

 higher combining proportion. I shall return immediately to 

 the consideration of those experiments by which Dr Brown 

 thought he had proved the truth of his view, so far as carbon 

 and silicon were concerned. Meanwhile, I proceed, very briefly, 

 to explain in what respect Professors Johnston's and Kane's 

 schemes of elemental isomerism differ from that we have been 

 discussing. 



Mr Johnston's views are founded on the existence of a class 

 of isomeric bodies not taken into consideration in Dr Brown's 

 speculations. The members of certain isomeric groups possess 

 not only the same proportion of elements, but likewise the 

 same atomic weight. They are not multiples or submultiples 

 of each other, like those already considered, but owe their 

 difference in properties to the relative grouping of their 

 molecules otherwise than by multiplication, or simple super- 

 addition of the atoms on each other. We have a group of 

 three such bodies in cyanuric acid, hydrated cyanic acid, and 

 cyamelide, compounds of carbon, oxygen, and nitrogen. "We 

 have another in aldehyde, metaldehyde, and eltaldehyde ; and 

 a well-known pair in urea and cyanate of ammonia.* These 

 isomerics possess the character of mutual convertibility: thus, in 

 a group of three, which we may term A, B, C ; A is convertible 

 into B and C ; B into A and C ; C into A and B ; and this without 

 addition or subtraction of any of their constituent elements. 

 Guided by these facts. Professor Johnston observes, that " the 

 speculations of chemists in regard to the probable diminution 

 of the number of received elementary bodies, have hitherto 

 run only in the channel of decomposition. * * * * The 

 idea of a possible transformation has hitherto hardly been 

 thought of ; and yet the doctrine of isomerism, rich already in 

 its numerous discoveries, has shewn that any number of the 

 received elementary bodies may be made up of the same ele- 



* Liebig's Familiar Letters, pp. 49, 50. 



