Page:Popular Science Monthly Volume 17.djvu/236

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224
THE POPULAR SCIENCE MONTHLY.

no matter what the substance may be of which they are composed, shed forth a pure firmamental blue; and that from them we can manufacture in the laboratory artificial skies which display all the phenomena, both of color and polarization, of the real firmament.

With regard to the production of the green of the spectrum by the overlapping of yellow and blue, Goethe, like a multitude of others, confounded the mixture of blue and yellow lights with that of blue and yellow pigments. This was an error shared by the world at large. But in Goethe's own day, Wünsch, of Leipsic, who is ridiculed in the "Farbenlehre," had corrected the error, and proved the mixture of blue and yellow lights to produce white. Any doubt that might be entertained of Wünsch's experiments—and they are obviously the work of a careful and competent man—is entirely removed by the experiments of Helmholtz and others in our own day. Thus, to sum up, Goethe's theory, if such it may be called, proves incompetent to account even approximately for the Newtonian spectrum. He refers it to turbid media, but no such media come into play. He fails to account for the passage of yellow into red and of blue into violet; while his attempt to deduce the green of the spectrum from the mixture of yellow and blue is contradicted by facts which were extant in his own time.

 

HOW ANIMALS EAT.
By HERMAN L. FAIRCHILD.

IN the digestion of the higher animals, the first act is the trituration of the food to assist and hasten its solution. We might term this mechanical digestion, as it is a reduction of the food preparatory to the essential physical and chemical process. Although very simple in

 
PSM V17 D236 Organs of the mouth in insects.jpg

Fig. 1.—Organs of the Mouth in Insects: 1. Trophi of a masticating insect (beetle): a, labrum or upper lip; b, mandibles; c, maxillæ with their palpi; d, labium or lower lip with its palpi.
2. Mouth of a butterfly: o, eye; f, base of antennæ; g, labial palp; h, spiral trunk or "antlia."
3. Mouth of a hemipterous insect (Nepa cinerea): l, labium; m, maxillæ; n, mandibles.