262 The late Dr. Thomas Thomson. 



tion on the part of Berzelius. He felt his authority to be as great as that 

 of Dr. Thomson, and with a temper more easily ruffled, he could not he 

 expected easily to bear the commendations and the censures that had for 

 years been awarded him by the Scottish chemist, according to the view he 

 took of his results. In the preface, also, to the " First Principles," there 

 may have appeared to Berzelius an excess of confidence on the part of its 

 author in the importance of his work, and something like an undervalu- 

 ing and setting aside of previous determinations. But nothing can justify 

 the lano-uage employed by Berzelius in the " Report " which he published 

 annually, and in which he also was in the habit of distributing judgment 

 with more freedom than could always be received with equanimity. I 

 shall not repeat the expressions ; but iu touching the moral character of 

 Dr. Thomson, as if he had purposely invented results, he showed how 

 little ho knew the man. Dr. Thomson was incapable of deceiving others 

 when not himself deceived, and that is the question alone worthy of our 

 attention. 



It was evidently the opinion of other chemists as well as of Berzelius, 

 that Dr. Thomson would not have reached the same perfection without 

 previously knowing the exact results he ought to obtain, supposing the 

 substances on which he operated to have been absolutely pure. How this 

 may be true, without taking from the genuineness of the experiments 

 to which the statement refers, is now understood by every practical 

 chemist. Dr. Thomson, as is well known, followed the example of 

 WoUaston in taking the atomic weight of oxygen for unity. Hydrogen 

 consequently became 0-125, and the rule he had laid down for his 

 guidance from Prout, enabled him to decide that the atomic weight of 

 every other element, and consequently of all bodies, must be a number 

 divisible without remainder, by 0-125, the atomic weight of hydrogen. 

 It is thus that an experimenter obtains a standard by which to test the 

 accuracy of his results, and it is only after repeated preliminary experi- 

 ments, and a continued reference to the table of equivalents, that he can 

 be certain of the removal of all his errors. 



In every case of more than usual precision, however, and particularly in all 

 debated cases, the chemist is expected to state every step in his progress. 

 He must tell the difficulties he has met with, and how they have been 

 obviated. Above all, he must satisfy other chemists that he knew the 

 purity, or the degree of purity of his materials, and especially their 

 hygromotric state at the moment when they were weighed. 



Now it is a very general opinion that Dr. Thomson did not give the 

 details necessary to inspire confidence in the accuracy of his results. He 

 has not even described the methods by which he prepared some sub- 

 stances, which, as we know, can only be produced in a state of purity by 

 tedious and difficult processes. The results, as they are stated, are at 

 the same time unusually and perplexingly exact. The consequence is, 

 that the work has exercised little of the influence which appears to have 

 been expected from it by its author. 



