276 ' Proceedings of the British Association 



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referred to Berthollet's views and experiments on this subject. The 

 measure or volume of bodies he thought might be represented with as 

 much facility as the weight; thus, for example, magnesia and sulphuric 

 acid may have their volumes numerically expressed before and after 

 combination, and also graphically by lines. Magnesia with sulphuric 

 acid showed a certain degree of condensation, lime a greater condensa- 

 tion, and barytes the greatest condensation ; and these he could repre- 

 sent and reason on as well by lines of different lengths as by figures or 

 by words. The degree of condensation (however expressed) had also 

 relation to the quality or degree of solubility. Thus, sulphate of mag- 

 nesia was very soluble, sulphate of lime but little soluble, and the 

 greatly condensed sulphate of baryta was insoluble. He then pursued 

 the analogy with the chlorids, comparing the chlorid of sodium with 

 the extreme case of the chlorid of silver. 



After graphically expressing the solubility of bases with sulphuric 

 acid by lines, he proceeded to show that the relative volumes of the 

 elements chlorine, bromine, and iodine could be perfectly represented 

 by lines equal in length. Prof, Dumas said that when a number of 

 metals are represented by lines, at first they seem in confusion, and it 

 would appear like an impossibility to arrange them in a system of lines 

 to permit their relations to appear; but when considered in relation to 

 the substitution of one property for another, or of the substitution of 

 one substance for another in groups, then their arrangement became 

 easy. And here we may remark, that Prof. Dumas had not previously 

 prepared diagrams or tables, but covered a large black board with lines, 

 figures, and formulae, to follow his train of reasoning, — and symbols, 

 volumes, and names were rapidly produced and as rapidly effaced to 

 illustrate the Professor's views of the laws of the substitution of one 

 body for another in a compound. Prof. Dumas gave many examples 

 of groups of other bodies, such as the alkalies, earths, &c., arranged 

 in the order of their affinities. He called attention in the Triad groups, 

 to the intermediate body having most of its qualities intermediate with 



the properties of the extremes, and also that the atomic or combining 

 number was also of the middle term, exactly half of the extremes added 

 together ; thus, sulphur 16, selenium 40, and tellurium 64. Half of the 

 extremes give 40, the number for the middle term. Chlorine 35, bro- 

 mine 80, and iodine 125. Or the alkalies, lithia, soda, and potassa, or 

 earths, lime, strontia, and baryta, afford, with many others, examples 

 of this coincidence; hence the suggestion, that in a series of bodies, if 

 the extremes were known by some law, intermediate bodies might be 

 discovered ; and in the spirit of these remarks, if bodies are to be | 



transformed or decomposed into others, the suggestion of suspicion is 

 thrown upon the possibility of the intermediate body being composed 

 of the extremes of the series, and transmutable changes thus hoped for. 



Prof. Dumas then showed that in the metals similar properties are 

 found to those of non-metallic bodies; alluding to the possibility that 

 metals that were similar in their relations, and which may be substituted 

 one for the other in certain compounds, might also be found transmuia- 

 lie, the one into the other. 



He then took up the inorganic bodies where substitutions took place 

 which he stated much resembled the metals- After discussing groups 



