CHEMISTRY AND PHYSICS IN RELATION 



able to declare what other condition will succeed the former one. The expression 

 of these conditions or relations, is what we term a natural law. 



THE DIFFERENCE BETWEEN THE CHEMISTRY OF THE PRESENT 

 LAY AND THAT OF AN EARLIER AGE. 



No one who is conversant with the history of the development of chemistry, 

 and of many other branches of physics, will deny that the main reason of the 

 advance of these sciences rests upon the gradually confirmed conviction that every 

 natural phenomenon has more than one requirement, every effect more than one 

 cause, and that it is the simple inquiry into the plurality of these conditions, and 

 the separation of effects which distinguish the chemistry of the present day from 

 that of former times. A speedy termination was put in the period of phlogosis 

 to all research by assuming principles of dryness and humidity, heat and cold, 

 combustibility, acidity, volatilization, &c. ; ascribing a special essence to every 

 property, the explanation of which was included in the simple description of the 

 phenomenon. 



The fluctuation in weight which bodies manifest on being submitted to chemical 

 processes, was regarded as a property of matter similar to the effervescence of 

 limestone, when acted upon by acids. There was a theory for the respective 

 phenomena of combustion and calcination, although the relations of weight were 

 not regarded as in the province of earlier chemistry. It was left to physiologists 

 to explain how a body could have an increase of weight after losing one of its 

 constituents ; and further, how under any -circumstance, a body can show a fluc- 

 tuation in weight. The increase of weight in calcination was an accidental pro- 

 perty, peculiar as it was supposed, together with many others, to metals. 



POINT OF VIEW ASSUMED Bf MANY PHYSIOLOGISTS OF THE 



PRESENT DAY, 



Many physiologists and pathologists still regard the conception of vital processes 

 and phenomena, from the same point of view as the phlogistics ; they ascribe the 

 effects of the nervous system to a nervous force ; while vegetation, irritability, 

 sensibility, action and reaction, simple effects of motion or resistance, causes of 

 the formation and the change of form, which are included in the expression of 

 typical forces, are all regarded as entities, and assume the place occupied in older 

 chemistry by the essences. 



CONFUSION OF EFFECT AND CAUSE. 



The most common phenomena have been incorporated in the minds of many 

 physiologists as actual capacities properties which they have falsely been led 

 to explain by especial reasons, different from the others known ; thus the terms 

 endosmosis, and exosmosis, have been applied to the r^Hirn to a state of equili- 

 brium of two fluids differing in their nature, or of two unequally dissolved 

 substances, separated by an animal membrane ; and thus we continue to treat 

 names as if they were facts, embracing an explanation of the process, while this 

 phenomenon is nothing more than a filtration, differing so far from other forms, 

 that the permeation is dependant not upon pressure, but upon attraction, disposi- 

 tion, or affinity. 



To this mode of observation was added the equally great error of conceiving 

 that causes must be of a similar nature to their results, and that like must call 

 forth like. Thus, the cause of combustion was thought to be something combus- 



