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THE POPULAR SCIENCE MONTHLY.

who shows his notions of accurate statement by asserting that, as I substitute "persistence" for "conservation," I therefore identify Persistence of Force with Conservation of Energy and debits me with the resulting incongruities—one who, in pursuance of this error, confounds a special principle with the general principle it is said to imply, and thereupon describes a wider principle as being included in a narrower (p. 481)—one who speaks of our "inner consciousness" (p. 488), so asserting, by implication, that we have an outer consciousness—one who talks of an inconceivable conception; ought surely to be aware how readily lax expressions may be turned into proofs of absurd opinions. And one who, in the space of a few pages, falls into so many solecisms, ought to be vividly conscious that a whole volume thus written would furnish multitudinous statements from which a critic, moved by a spirit like his own, might evolve abundant absurdities; supplying ample occasion for blazoning the tops of pages with insulting words.

MORE ABOUT THE GRAPE-VINE PEST.

By CHARLES V. RILEY, M. A., Ph. D.

THE number of true (grape-vine) species of Vitis, with the cohering petals falling off when the flower opens, and bearing edible fruit, in the territory of the United States, is limited to nine. Of these, four species, viz., Vitis Labrusca, or Northern Fox; Vitis æstivalis, summer grape; Vitis riparia, river-bank grape; and Vitis vulpina, Southern Fox or Muscadine, are of chief practical consequence as having yielded our different cultivated varieties.

I will now proceed to indicate the relative susceptibility to the disease of the cultivated species and varieties. For the sake of conciseness, it will be best to indicate this susceptibility by letters and numerals, as follows:

0—No perfect leaf-galls found; or not at all subject to them.
a—Leaf-galls very rarely found.
b—Leaf-galls not unfrequently found.
c—Leaf-galls abundantly found, or very much subject to them.
0—Entirely free from root-lice.
1—Having the root-lice in unusually small numbers, but countervailing their punctures.
2—Root-lice often numerous; vines sometimes suffering from their effects.
3—Most subject to the root-lice and dying from their attacks whenever the condition's are favorable to their increase.

European Grape (vinifera), 0, 3.—The very few exceptions, where galls have been found on the leaves of this species, will scarcely invali-