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the ambient air by the chemical law of gaseous diffusion. Does any one suppose that, amid sources of contamination, stagnant water would be purer than running? Had Dr. Niemeyer used his nose, or attended to its monitions in his midnight ramblings among the .sick, he could never have penned such an erroneous sentence. Only solicitation that your journal shall occupy the highest grounds in all its selections animates this criticism from my pen.
J. R. Black.
Newark, Ohio, December 22, 1877.
"THE LAW OF CONTINUITY."
To the Editor of the Popular Science Monthly.
In the interest of scientific accuracy, I would call attention to one or two statements in the article on "The Law of Continuity," in your November number, which are either greatly strained or positively erroneous.
The author of the article in question says, speaking of sulphuric acid and water, "In all possible percentages do these liquids chemically combine, and this is at variance with the generally obeyed law of definite proportions" (page 32—the italics are mine). This is a very loose use of language, as may be easily demonstrated by a comparison of this passage with the statement of the fact by any scientific authority. For example, Fownes ("Manual of Chemistry," eleventh edition, p. 203) says: "The most concentrated sulphuric acid, or oil of vitriol, as it is often called, is a definite combination of 40 parts sulphuric oxide and 9 parts water. ... Oil of vitriol is not the only hydrate of sulphuric oxide; three others are known to exist. When the fuming oil of vitriol of Nordhausen is exposed to a low temperature, a white crystalline substance separates, which is a hydrate containing half as much water as the common liquid acid. Further, a mixture of 98 parts of strong liquid acid and 18 parts of water, 2H2OSO3, or H2SO4H2O, congeals and remains solid even at 7.2° C. (45° Fahr.)," etc. There is, then, in the case of sulphuric acid and water, at least, a clear enough distinction between mechanical mixture and chemical combination, although Mr. lies quite loses sight of it.
Then, again, he says (p. 30), "Science is unable to give us any metal but gold in a translucent state." The inability does not lie with "science." It has long been known that silver may, by chemical means, be obtained in a translucent film. And likewise platinum, aluminum, bismuth, copper, lead, iron, nickel, cobalt, palladium, zinc, cadmium, magnesium, and other metals, have been procured in a layer so thin as to be transparent (Wright, American Journal of Science and Arts, No. 73, January, 1877).
Launcelot W. Andrews.
Springfield, Mass., November 8, 1877.
COOK AND HIS "BIOLOGY:"
THE Rev. Joseph Cook seems to have attained the position of an accepted champion of orthodoxy in its conflict with the science of the time, and as such must have a degree of attention to which he is not otherwise entitled. In the delivery of the lectures which compose his volume on biology, he was listened to, we are told, by large audiences of cultivated and scholarly men, who applauded him enthusiastically; while the book has been highly praised by eminent theologians and numerous newspapers, and has had a brisk and extensive sale. Yet we observe that the tide of encomium is perceptibly falling, and shrewd orthodox people are beginning to see that they cannot too quickly relieve themselves of responsibility in regard to his work. In an able review, in the January New-Englander, the scientific charlatanry of Mr. Cook's book is thoroughly exposed; its taste and rhetoric are pronounced "execrable," and the writer closes by saying that "this production is not one for orthodoxy to be proud of, and that it is best to declare this opinion plainly and promptly."Nevertheless there is a startling significance in the fact that such a work could have received from an intelligent Christian community the measure of commendation that has been accorded
- It is but fair to say that the article in question was written and in the hands of the editor six months before Prof. Wright's researches were published. Ed.