310 REPORT — 1859. 



already made many experiments upon the former. As I have not attempted 

 anything in this direction as yet, I shall not dwell upon these subjects; the 

 more so, as I believe I have fulfilled the object with which this preliminary 

 report was written ; namely, to give an idea of the character of the work I 

 am engaged in, and the manner in which I propose to execute it. In con- 

 clusion, I shall only say a few words on one other feature of my plan of re- 

 search which I hold to be of paramount importance. Hitherto I have only 

 alluded to the subject of atomic volume, as a secondary element of morpho- 

 logical classification (isatomes and polyatomes). This has not arisen, how- 

 ever, from want of appreciation of the great benefits which chemical theory has 

 derived from the introduction of the doctrine of atomic volume into science, 

 and especially from the labours of Kopp and others in connexion therewith. 

 The opinions put forward by Avogadro, Hunt, and others, whatever may be 

 their intrinsic merit, show us that there exists as yet much room for diversity 

 of opinion. On this account I will not, in the first instance, introduce the 

 element of volume at all into the discussion of my numerical results. Many 

 experimentalists have used in their experiments on points connected with 

 molecular physics, quantities of the bodies operated upon which bear no 

 relation to the proportional weights, according to which all chemical com- 

 bination takes place. The remarkable laws of combination are too univer- 

 sally true to allow us to doubt that, although there maybe a difference 

 between chemical and physical molecules, there must be some simple mul- 

 tiple relations between them. The remarkable relation established by Du- 

 long between the proportional weights (equivalents) of bodies and their 

 specific heat, is a striking confirmation of this opinion. In all the experi- 

 ments which I propose to make, I will, as I have likewise heretofore done, 

 always use the bodies operated upon in equivalent proportions. If we experi- 

 ment on the physical properties of a single homogeneous substance, it makes 

 no matter what quantities are employed, because by a simple calculation we 

 can reduce our numerical results to equivalent quantities ; it is quite other- 

 wise, however, when we operate upon mixtures, for here any excess over 

 the equivalent quantity influences the results, especially if we assume solution 

 to be a chemical process. In this way I hope to be able to avoid all per- 

 plexing anomalies, arising from the presence of an excess of one constituent 

 in a solution, which could interfere with the ready perception of any law 

 governing the phenomena. 



Provisional Report on the Progress in the Solution of certain Special 

 Problems in Dynamics. By A. Cayley, F.R.S. 



The author stated the reasons which delayed the furnishing of the full Re- 

 port, which he hoped to have ready for the next Meeting of the Associa- 

 tion. 



