246 An Essay on the Signs of Ideas. 
more facility, clearness, and strength, and 
are much more durable than those of others. 
It may be asked then, in reference to this 
circumstance,—Of which class of simple sen- 
sations, have we the strongest, most distinct, 
and most lasting ideas ? 
The answer is, Of those of sight. After 
the lapse of years we still retain nearly perfect 
ideas of persons and places which we have 
but once seen ;—so Ovid, in his epistles, beau- 
tifully says, 
« Tila meis oculis species abeuntis inheret, 
« Cum premeret portus classis itura meos.” 
which may be thus rendered, 
Still do mine eyes the dismal sight retain, 
When thy departing vessels ploughed the main. 
The ideas of sounds come next in respect 
of vigour and durability. We remember 
sufficiently well the voices of our friends and 
acquaintances. We can repeat in our minds 
a variety of tunes which we have once heard, 
and receive pleasure from them without the 
actual production of any sound. 
Whether we ever have ideas of sensations 
received by the nose and mouth appears to me 
uncertain ; if we have, they are certainly 
much weaker and more transient, than those 
just mentioned, so that in a short time they 
fade entirely away. 
