70 EXPERIMENTS, &c. 



and the head in relation to the shoulders, to in^ 

 cline the trunk of the body backward, until we 

 bring the optic axes to a third star, this will ap- 

 pear still higher than the second was perceived 

 to be. If instead of directing the eyes succes- 

 ^sively to different objects, the same object be 

 suffered to remain at the concurrence of the 

 optic axes in all these different positions of the 

 body, it is evident, that it must be seen to move, 

 during the change from one position to another. 

 The facts I have mentioned are so obvious, 

 that I should not have spoken of them, had I 

 not intended they should introduce the follow- 

 ing question : What is there within us, to in- 

 dicate these positions of the body ? To me it 

 appears evident, that since they are occasioned 

 and preserved by combinations of the actions of 

 various voluntary muscles, some feeling must 

 attend every such combination, which suggests, 

 from experience perhaps, the particular posi- 

 tion produced by it. But in almost all the posi- 

 tions of the body, the chief part of our muscular 

 efforts is directed toward sustaining it against 

 the influence of its own gravity. Each posi- 

 tion, therefore, in which this takes place, must 

 be attended with a feeling, which serves to in- 

 dicate its relation to the horizontal plane of the 

 earth ; and consequently, if aur bodies pos- 

 sessed no gravity, or, if the thing were possible, 



