THE CHEMICAL PROBLEMS OF TO-DAY. 365 



been taken away from us before old age had naturally limited him. 

 Bunsen we still rejoice to call ours, who now, allowing the tools of his 

 work to drop from his hand, looks forth to the evening of his life in 

 quiet, happy leisure. May he be permitted for a long time to look back 

 upon a life filled with greatest scientific achievements; may his calm, 

 friendly eye rest for many years upon the incomparable picture of his 

 beloved Heidelberg. 



We have mentioned spectral analysis, though it has been almost for 

 an age the common property of science. Let us also cast a grateiul 

 retrospect upon a deeply furrowing revolution — of which chemistry 

 also, for several decades, has boasted as a substantial possession — upon 

 the development of the doctrine of structure., that solid theoretical foun- 

 dation from wliich the proud edifice of modern organic chemistry rises. 

 A generation has grown up around us which has received as a matter 

 of fact this doctrine wliich still seems new to us older ones. But those 

 far-seeing men, whose eyes recognized the immensely simple in the seem- 

 ingly impenetrable complication of the carbon compounds, are still ac- 

 tively alive amongst us, and it is their happy lot to reap in their own 

 activity what once they sowed in juvenile work. Here the eye is di- 

 rected upon the master of chemical research — August Wilhelm von 

 Hofmann ; before all upon his researches upon the organic nitrogenous 

 bases, — researches which do not find their equal in organic chemistry 

 and which, even more perfectly than Dumas' fundamental discovery of 

 trichoracetic aciJ, allowed the fundamental conception of substitution 

 to expand into the living consciousness of chemists, at first, curiously, 

 by snpporting the theory of types in organic compounds and then by 

 promoting the transition to the structural or constitutional view, which 

 at present embraces, with unparalleled perfection, the whole territory of 

 organic compounds. 



But the suggestion of this doctrine, which finds its crowning success 

 in the recognition of the inner aggregation of the atoms, is associated 

 for all time with the name of a man who, although a master of rare art 

 in experimenting, knew how to surpass what he had achieved at the 

 laboratory table, by the convincing power of his speculative work. We 

 can not here dispute the part which other eminent chemists have taken 

 in the development of the doctrine of structure — there are, Butlerow, 

 Cooper, Erlenmeyer, Frankland, Kolbe, Odling, Williamson — but the 

 glorious guide in this great and victorious movement forward, he, to 

 whose eyes was disclosed not only the tetra-valeuce of carbon, but also 

 the solution of the problem of the constitution ot organic compounds, 

 in the recognition of the property of carbon atoms to be linked to each 

 other by their valencies ; he is the philosopher of organic chemistry — 

 August Kekule. The name of this discoverer, who also started upon 

 his high and soaring flight from Heidelberg, is justly mentioned alone 

 when we want to recall in a word the putting forth and the development 

 of the leading chemical theories. 



