No. 7. J WURTZ — THEORY OF ATOMS. 385 



uow obtaiued from coal-tar,, the impure source of so mauy wou- 

 ders. Such, is a discovery which has issued from the womb of 

 science, and of science the most abstract; confirming precon- 

 ceived ideas on the relations of composition and of atomic struc- 

 ture between anthracene, alizarin, and the intermediate terms. 

 And this will not be the last product of this beautiful develop- 

 ment of chemistry. Future conceptions on the intimate structure 

 of complex organic compounds will b3 so many landmarks for 

 new syntheses, and hypotheses rigorously deduced from acquired 

 principles will be fruitful in the happiest applications. 



Saccharine matters, alkaloids, other complex bodies whose 

 properties and diverse transformations are actively investigated 

 with a view of deducing: their molecular constitution — all these 

 substances may be artificially reproduced, as soon as this pre- 

 paratory work, so difficult and often seemingly so useless, will 

 have sufficiently advanced. So fine a programme justifies the 

 great efibrts which have been made, in our days, in this direc- 

 tion. To discover, to analyse, to study, to classify, reproduce 

 artificially so many diverse substances, to study their internal 

 structure, to indicate their useful applications; to surprise, in a 

 word, the secrets of Nature and to imitate her, if not in her pro- 

 cesses, at least in some of her productions — such is the noble aim 

 of contemporary science. She can only reach it by the sure but 

 slow paths we have indicated ; experiment guided by theory. lu 

 chemistry, at least, empiricism has had its day; problems, clearly 

 stated, must be boldly faced, and henceforth the rational con- 

 quests of experiment will only leave a place more and more 

 circumscribed for fortunate finds and the surprises of the crucible. 

 Away, then, with the detractors of theory, who go in quest of dis- 

 coveries which they can neither foresee nor prepare ; they reap 

 where they have not sown. But you, courageous workers, who 

 trace methodically your furrows, 1 congratulate you. You may 

 be sometimes deceived, but your work will be fruitful, and the 

 goods which you amass will be the true treasure of science. 



Will not this science be one day embarrassed and as if encum- 

 bered with so much riches, and w ill the strongest memory be 

 able to support all the weight ? If the danger exists, there is no 

 need to fear it. The classification of all these materials will free 

 us from embarrassment. In a well-arranged edifice, each stone 

 requires to be prepared before taking its place ; but the con- 

 struction accomplished, all do not strike the eye equally, though 



