The essential oil of almonds in a bottle that contains a good deal of air-oxygen, and but a very little of the oil, spontaneously passes into another odoriferous body, benzoic acid; which is seen in crystals to form over the dry parts of the flask.  This is a natural illustration of this idea.  In giving the recipe for “sweet pea” as above, we form it with the impression that its odor resembles the orange-blossom, which similarity is approached nearer by the addition of the rose and tuberose.

The vanilla is used merely to give permanence to the scent on the handkerchief, and this latter body is chosen in preference to extract of musk or ambergris, which would answer the same purpose of giving permanence to the more volatile ingredients; because the vanilla strikes the same key of the olfactory nerve as the orange-blossom, and thus no new idea of a different scent is brought about as the perfume dies off from the handkerchief.  When perfumes are not mixed upon this principle, then we hear that such and such a perfume becomes “sickly” or “faint” after they have been on the handkerchief a short time.

PINE-APPLE.—­Both Dr. Hoffman and Dr. Lyon Playfair have fallen into some error in their inferences with regard to the application of this odor in perfumery.  After various practical experiments conducted in a large perfumatory, we have come to the conclusion that it cannot be so applied, simply because when the essence of pine-apple is smelled at, the vapor produces an involuntary action of the larynx, producing cough, when exceedingly dilute.  Even in the infinitesimal portions it still produces disagreeable irritation of the air-pipes, which, if prolonged, such as is expected if used upon a handkerchief, is followed by intense headache.  It is obvious, therefore, that the legitimate use of the essence of pine-apple (butyric ether) cannot be adapted with benefit to the manufacturing perfumer, although invaluable to the confectioner as a flavoring material.  What we have here said refers to the artificial essence of pine-apple, or butyrate of ethyloxide, which, if very much diluted with alcohol, resembles the smell of pine-apple, and hence its name; but how far the same observations are applicable to the true essential oil from the fruit or epidermis of the pine-apple, remains to be seen when we procure it.  As the West Indian pine-apples are now coming freely into the market, the day is probably not distant when demonstrative experiments can be tried; but hitherto it must be remembered our experiments have only been performed with a body resembling in smell the true essential oil of the fruit.  The physical action of all ethers upon the human body is quite sufficient to prevent their application in perfumery, however useful in confectionary, which it is understood has to deal with another of the senses,—­not of smell, but of taste.  The commercial “essence of pine-apple,” or “pine-apple oil,” and “jargonelle pear-oil,” are admitted only to be labelled such, but really are certain organic acid ethers.  For the present, then, perfumers must only look on these bodies as so many lines in the “Poetry of Science,” which, for the present, are without practical application in his art.