512 Evolution of the Doctrine of Affinity. 



are not in so dangerous a plight as might at first appear. 

 The thermal doctrine of affinity has had no more real influence 

 on the steady experimental evolution of Chemistry than had 

 the electrochemical theory of Berzelius. Both long held 

 honourable places as great general truths ; attempts have been 

 made with both to apply them to experimental details ; but, 

 as frequently happens, theory and experiment did not agree, 

 the theory has been calmly ignored, and we must trust to the 

 future to make things plain. If, once again, a theory has 

 unexpectedly proved untenable, once again the old course of 

 events will be repeated ; attempts at generalization have been 

 too soon made : " gestit enim mens exsilire ad magis gene- 

 ralia ut acquiescat ; (Bacon). Theory has attempted to 

 precede fact; it has pursued a false path, and must wait 

 until fact with quiet progress shows the way. 



Such is our present state of knowledge. But long before 

 the thermochemical doctrine of affinity became untenable, the 

 efforts of investigators had been directed to ascertaining the 

 conditions on which chemical reactions depend, such as the 

 influence of time, of temperature, of mass, and of solvents ; 

 and to the measurement of the resulting changes in volume, 

 in evolution of heat, and similar phenomena. Now that ex- 

 periment has shown the fallacy of an attempt to deduce 

 chemical change from the fundamental principles of thermo- 

 chemistry, we hail with joy the appearance of a new, really 

 kinetic, doctrine of affinity , which, quietly and unostenta- 

 tiously making its way along the road of induction, holds out 

 to us the prospect of a real knowledge of the essential nature 

 of chemical change. By its help also those numerous thermo- 

 chemical observations, which were unable to lend support to a 

 onesided theory, for which they furnished the sole basis, 

 acquire for the first time their true meaning when viewed in 

 connexion with all other phenomena accompanying chemical 

 change. Thus, although one illusion more has been dissi- 

 pated by this new evolution of the doctrine of affinity, yet 

 science is enriched by the acquisition of a less hypothetical 

 and more far-reaching and inclusive conception of the nature 

 of chemical combination.* 



* A short paper by Mr. Clarence A. Seyler, " On the Thermal Equi- 

 valents" of some elements and groups, has been published in the 'Chemical 

 tyu*~ • News ' of April 1, vol. lv. p. 147. 



