186 NATURE AND LIFE. 
certain definite degrees, as sounds act on the auditory 
nerves. There is, so tospeak, an octave of smells, as there 
is an octave of tones; some perfumes accord, like the 
notes of an instrument. Thus almond, vanilla, heliotrope, 
and clematis, harmonize perfectly, each of them producing 
almost the same impression in a different degree. On the 
other hand, we have citron, lemon, orange-peel, and ver- 
bena, forming a similarly associated octave of odors, in a 
higher key. The analogy is completed by those odors 
which we call half-scents, such as the rose, with rose-gera- 
nium for its semitone ; ‘ petit-grain’ and neroli, followed by 
orange-flower. With the aid of flowers already known, by 
mixing them in fixed proportions, we can obtain the per- 
fume of almost all flowers.” In accordance with these fan- 
cies, Piesse has formed gamuts of odors, parallel with musi- 
cal gamuts, and exhibiting concords of scents at the same 
time with those that produce discords. As a painter blends 
his tints, the perfumer should blend his fragrances; and 
Piesse maintains he can only gain that object by. following 
the laws of harmony and contrast in odors. This theory is 
certainly quite ingenious, and deserves attention, but it is 
open to serious objections. If the harmony of colors and 
of sounds exists, it is because optics and acoustics are ex- 
act sciences, and harmony in this case is reduced to nu- 
merical relations, determined in a positive way. These re- 
lations, as concerns odors, can have no other basis than a 
capricious and relative sensibility. They are thus incapa- 
ble of being reduced to form, @ fortiori of being translated 
into fixed precepts. 
To complete these details, it remains to say something 
of the delusions of the sense of smell; for this sense, like 
the others, has its aberrations and hallucinations. The de- 
lusions of smell are hardly ever isolated ; they accompany 
those of hearing, sight, taste, and touch, and are also less © 
frequent than the latter. Insane people, who are affected 

