i 4 4 THE POPULAR SCIENCE MONTHLY. 



solid or fluid, placed on moistened glass, or in a saucerful of water, 

 instantly act on those molecules of the liquid which they touch, and 

 repel them more or less, producing a vacuum. He judged that this 

 method might serve to make odors sensible to sight, and enable us to 

 distinguish odorous from inodorous bodies. These movements of 

 odorous bodies on the surfaces of liquids, of which camphor particu- 

 larly gives so curious an instance, have lately been studied with the 

 greatest care by a French physiologist, with a view to establishing 

 a theory of odors. With this purpose Liegeois has examined most 

 of the odoriferous substances, and has ascertained that almost all of 

 them perform various motions of circulation and displacement on the 

 surface of water, resembling those noted with camphor. Some act 

 precisely as camphor does. Among these are benzoic acid, succinic 

 acid, the rind of bitter oranges, etc. With others, motion soon stops, 

 for they are quickly surrounded by an oily film which keeps them 

 confined. Some must be reduced to powder before the phenomenon 

 takes place. As regards odorous liquids, it occurred to Liegeois 

 to saturate very light and spongy seeds, themselves odorless, with 

 them, and he then found, on throwing the seeds on water, that circu- 

 latory and displacing movements took place, as with other substances. 

 He concluded, from a series of experiments methodically tried, that 

 the motions in question must be attributed, not to a release of gas, 

 acting in the manner of a recoil, but simply to the separation and 

 rapid diffusion, within the water, of the odorous particles. The vola- 

 tility of substances cannot be admitted to have any part in explaining 

 the phenomenon. It depends wholly on the aifinity of fluids for 

 the odorous particles, and also for those of fatty matter. Liegeois 

 found, for instance, that a drop of oil put on the surface of water, 

 without sensibly lessening in size, emits an enormous quantity of 

 microscopic droplets, which are diffused through the mass of the water. 

 Aromatic essences produce a like effect. Though insoluble in water, 

 they have a powerful tendency to disperse themselves throughout it, 

 and water that receives a very small quantity of the odoriferous 

 principle, in the shape of extremely fine powder, has enough to gain 

 their perfume completely. Liegeois's experiments give proof of the 

 most diligent labors and of praiseworthy sagacity. Science has ac- 

 cepted them with satisfaction, and, after employing them usefully, 

 will preserve the memory of their author, taken away in the flower of 

 his age, at the outset of a noble career as a physiologist and surgeon. 

 It seemed, to quote his words, as though in these experiments we 

 were assisting at the formation of the odorous molecules. Those 

 delicate atoms emitted from odorous substances and diffused through 

 the atmosphere are, in fact, the very same that impinge on our pitui- 

 tary membrane, and give us the sensation of odors. Moreover, facts 

 long ago observed display this revealing action, so to call it, of water 

 upon odors. At morning, when the verdure is moist and the flowers 



