of the Position of Sonorous Bodies. 55t 
the part below the elbow was kept in an horizontal 
Position with the hand turned downwards, which 
was done by the operator himself. After taking 
these preparatory steps, the man bent his body 
forwards in a situation which presented the 
profile of his face nearly to the front of his 
hearer, whilst his mouth pointed to the cup; in 
which posture he copied the voice of a confined 
child so completely, that three positions of the 
glass were easily distinguished by as many diffe- 
rent tones, viz. when he pressed the mouth of the 
cup close against the palm, when one edge of it 
was elevated, and when the vessel was held near 
the hand but did not touch it. The second and 
third instances of ventriloquism afford strong 
proofs, that this delusive talent is nothing more 
than the art of substituting an echo for the pri- 
mary sound; for, besides the change perceivable 
in the direction of the voice, it was found to 
be blended with a variety of secondary sounds; 
such as we know by experience are produced as 
often as a noise of any kind issues from a cavity. 
J have already made some remarks on this spe- 
cies of knowledge; but it would be improper to 
dismiss the subject without noticing the accu- 
racy, with which the ear recognizes the finer 
modifications of sounds, and their causes, I 
have frequently observed, that a certain waterfall 
makes a flatter and duller noise when the ground 
