306 Dr Robert E. Brown on the 



motions, both physical and vital ; their relative proportion in differ- 

 ent regions, and at different times — can we, I think, expect to gain 

 a true insight into the operations of nature. For a perfect know- 

 ledge of these things would place us at its very fountain-head, whence 

 we might survey its manifold operations, — predicate results in circum- 

 stances beyond our observation, — and even, perhaps, exercise some 

 direction and control over its acts, or regulate our own actions in its 

 light. Such a knowledge, perhaps, transcends our powers ; never- 

 theless the parallel instance of astronomy indicates that a great ap- 

 proach to it may be made. The perfection of this science comes 

 from the discovery of the law of gravity, and from our, therefore, 

 viewing the physical motions of nature from the source whence they 

 are directed ; and when the laws of other forces are as well known, we 

 may perhaps have all natural sciences, physical as well as physiolo- 

 gical, approaching in exactness and perfection to astronomy. 



If these views be admitted, it would be a matter of some conse- 

 quence to know the comparative energies of the different forces in 

 different regions and localities of the earth. The force of gravity 

 may be perfectly ascertained by the methods already in common use. 

 But it is scarcely probable that the variations in this force which occur 

 in the earth, are sufficient to produce much influence on actions, 

 either physical or vital. The sensible effect which we see the change 

 in gravity produce upon the movement of the pendulum, however, 

 shews that it must not be overlooked in any inquiry into the compa- 

 rative energy of the forces. The cohesive force in different places 

 might possibly be accurately estimated by their temperatures; and 

 an approximation to the vital forces, again, might perhaps be arrived 

 at by ascertaining the intensity of solar light and heat. This, how- 

 ever, it would require experiment to determine. For the measure- 

 ment of the heat which accompanies light, does not give the measure- 

 ment of light ; and it is, therefore, questionable whether the chemi- 

 cal and other forces of sunlight bear any constant pi'oportion to its 

 luminosity, and whether they could be estimated in the way we have 

 mentioned. With regard to the variations of chemical force, if such 

 occur, and without which our knowledge of all the others could lead to 

 no result, they might possibly be determined by ascertaining the 

 amount of chemical action which takes place between two or more 

 agents in different places, under the same circumstances, and in a 

 given time. It may perhaps be found, however, that chemical ac- 

 tion and vital action generally jn-eserve the same proportion in their 

 increase or decrease, and that the knowledge of the one will, in most 

 cases, inform us as to the state of the other. 



Among the many bearings which a knowledge of these circumstances 

 might be expected to have upon various departments of knowledge, 

 I foresee none which promise more practical utility than those which 

 it seems likely to have upon many of the diseases to which man is 



