Page:Popular Science Monthly Volume 7.djvu/195

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refractive object. The reader will note that not only the details of the markings are greatly changed, but the very outline of the figures.

The fact that the most skillful microscopists of the age all differ upon the true appearances of a common and not very minute object, and the microscope itself presenting to the vision the most opposite appearances of one and the same object, should act as a caution to those who accept too readily theories based upon microscopical research; and suggests that, in the cause of justice, when life is at stake, single-handed evidence relating to the microscopical examination of apparent blood-stains should be verified at least by a second person before being accepted.

Thus we see that the so-called revelations of the microscope are but hieroglyphics, needing the interpretation of a mind of the highest culture, and that while the microscope is a good servant it is a bad master—mighty in the hands of a Huxley, but as useless to a man without the powers of discrimination as the chisel of Michael Angelo would be in the hands of a Modoc.



S understood by us, the migration of a bird is simply the desertion of a given locality by that species for a certain, and always the same, portion of each year. As an example, the common house-wren (Troglodytes ædon) is migratory, in that it remains in New Jersey only from late in April until late in September, having left its Southern home for six months.

Before endeavoring to determine the causes of this movement on the part of some birds, we must first note the various features characterizing the movement itself; for it may safely be asserted that no two birds migrate alike, although the similarity is marked among the various species of the same family. The most marked feature in migration is the apparent uniformity in the time of its occurrence, i. e., of the dates of the arrivals in spring, and of the departures in autumn. Is this arrival in spring as regular as claimed by some, and supposed by most people? To the casual observer, and, indeed, to many who have for years noted the first appearances of our various birds, the arrival seems to be quite regular; and, curiously enough, we find many such observers insisting that, however late a bird may be any one season, he is never earlier than a given date. Thus we 