40 CHEMISTRY AND PHYSICS IN RELATION 



chemical and physical properties of the elements have remained constant in 

 many of these combinations ; and in those, where there is a deviation in color, 

 solubility, &c., one property, namely, physical form, remains constant. The same 

 or a similar relation is doubtlessly attainable between the properties of all elements 

 and their combinations, and all the efforts of chemistry have been directed to the 

 discoveries of these constant relations. An investigation of this kind is the only 

 way in which chemistry can attain to natural laws, and it is only by the same 

 means that physiology, if it is to rise to the rank of a natural investigation, can 

 gain a scientific basis. 



THE CHEMICAL FORCES OF THE ELEMENTS HAVE A SHARE 

 IN THE VITAL PROPERTIES. 



We cannot, certainly, as yet, follow out any physical property by means of the 

 laws or properties of the elements ; but still there can be no question, that a 

 knowledge of such properties is to be gained from laws, which arise when these 

 elements have been, in a certain measure, arranged. When these elements have 

 combined to form an animal or vegetable substance ; when they have attained to 

 physiological or vital properties ; then the chemical forces, which have given them 

 their original properties are no more destroyed or removed, than the cohesive 

 power of the atoms of sulphur is destroyed when we melt a portion of that 

 substance. There has only been another cause superadded heat which has 

 removed the effect of the cohesive force, or the connection, rendering its action 

 no longer perceptible. The new condition, that of fluidity, is one of equilibrium 

 between two antagonising causes, an effect in which both have an equal share. 



In vegetable and animal substances, the elements obey mechanical and chemical 

 laws, if their action be not^removed by resistances, which must be regarded as the 

 indications of new laws, that govern the parts of the organism. 



THE RELATIONS BETWEEN CHEMICAL AND VITAL EFFECTS MUST 



BE INVESTIGATED. 



If by the connection of many causes, new laws and phenomena are brought 

 forward, which have no resemblance with the actions of individual causes in 

 themselves, the effects of the latter stand in an immediate relation to those of the 

 new phenomena, and these are the relations which must be sought and investigated. 



When we have gained a clear conception of these, we shall be able to decide 

 concerning a number of unknown facts or phenomena, as in the case of 

 isomorphous substances, without further observation. 



THE RELATION OF THE WEIGHTS OF THE ELEMENTS TO CHEMICAL 



COMBINATIONS. 



A purely scientific character has been imparted to chemistry by the knowledge 

 of the fact, that the property of weight in all chemical combinations is constant, 

 and that, in whatever manner the elements may be composed, the weigh' t of the 

 combination is equal to the sum of the weight of its elements. The knowledge 

 of chemical proportions has led to our being able to predetermine all possible 

 combinations of a body; but it could not explain the apparent exceptions of bodies, 

 which, according to experience, united not in constant, but in every conceivable 

 proportions. It is by the consideration of -another property the relation of 

 external form to composition that we have not only been enabled to give an 

 explanation of these deviations, but have also gained a far clearer conception of 

 the cau?e of the pjisia*rt"relations of combination. 



THE UNIVERSALITY OF LAWS OF MUTUAL DEPENDENCE 

 IN NATURAL PHENOMENA. 



The advances made in all branches of natural investigation, in the physical 



