256 The late Dr. Thomas Thomson. 



wbich he treats, and in imagining such a work, we see how ready Dr. 

 Thomson was to turn all his labours to account. In the "Annals" also were 

 Comx)tes rendus of the proceedings of the Royal Society. Every chemical 

 paper read there was reported with an exactness which will astonish any 

 one who looks back at the array of figures and of facts, and who also 

 knows that they were transcribed from memory alone. I have heard 

 Dr. Thomson explain that the rules of the Society prevented the taking 

 of notes with a view to publication before the appearance of the 

 " Transactions," and that he consequently applied himself to the com- 

 mitting to memory even of numerical statements for insertion in the 

 following number of the Annals of Philosophy. As soon as possible, 

 after leaving the meeting, he transferred to paper what he had carried 

 away, after which be could not have remembered more of it than the 

 general facts. 



I shall now relate the part Dr. Thomson took in the promulgation of 

 the Atomic theory, and I shall do so at some length, as I think he has 

 not received due credit for the share he had in the progress of that great 

 work. I reckon this the most important proceeding of his life, unless we 

 place before it his System of Chemistry, the influence of whose earlier 

 editions it is difficult to estimate. On the 26th of August, 1804, Dr. 

 Thomson went to Manchester, and saw for a day or two much of Mr. 

 Dalton, who explained to him his views on the composition of bodies. 

 He saw at a glance, as he tells us, the immense importance of such a 

 theory, and was delighted with the new light which immediately struck his 

 mind. He wrote down at the time the opinions which were offered, and 

 three years later, when about to publish the third edition of his System 

 of Chemistry, he obtained Dalton's permission to insert the sketch he had 

 taken, before Dalton himself had given it to the world. The theory was 

 at that time very slenderly supported by facts, for chemists possessed 

 few experiments which could be considered as even approaching to 

 accuracy. Up to the time when Thomson published the sketch, he seems 

 to have been Dalton's only convert. Perhaps no other chemist had 

 taken the trouble to listen to it, if we except Dr. Henry of Manchester, 

 who was Dalton's frequent visitor, but there is no probability that even 

 he at so early a period accepted the theory, for he speaks of it, so late as 

 .1810, in rather doubtful terms, in the sixth edition of his "Elements." 



Thomson's paper on the oxalates, read to the Royal Society in 

 1807, contained the first direct example of the application of the Daltonian 

 theory to supersalts. He there shows that oxalic acid unites with 

 strontian as well as with potash in two different proportions, and that the 

 quantity of acid combined with each of these bases in their superoxalates, 

 is just double of that which saturates the same quantity of base in their 

 neutral compounds. During the same year Dr. WoUaston read his famous 

 paper on the oxalate, binoxalate, and quadroxalate of potash, and ho 

 commences it with a relation of what Thomson had already done. He 

 states that he had remarked the same law to prevail in various other 



