Page:Popular Science Monthly Volume 13.djvu/656

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THE POPULAR SCIENCE MONTHLY.

in the sparrow, offensive to many persons. Item, nervous invalids are fretted and annoyed into positive illness by the unceasing noisiness of these birds. 5. "They (the sparrows) have at present practically no natural enemies, nor any check whatever upon limitless increase," though, even with the most unobjectionable species of birds, a check would be desirable. And now what course must we adopt in order to abate this sparrow nuisance?—for abate it we must, or else the sparrows will eat us all out of house and home. Dr. Coues's recommendations on this head are: 1. Let the birds shift for themselves. Take down the boxes and all special contrivances for sheltering and petting the sparrows; stop feeding them; stop supplying them with building-material. 2. Abolish the legal penalties for killing them. "Let boys kill them if they wish. Let them be trapped and used as pigeons or glass balls in shooting-matches among sportsmen." This last recommendation shows very plainly that Dr. Coues has lost all patience with the sparrow. For ourselves, we hope the evil will be checked by some different means.

 

Agencies of Nitrification.—The researches of Schloesing and Müntz in nitrification have resulted in the very important discovery of a nitrifying organism analogous to the ferment organism of yeast. The evidence of the existence of a nitrifying organism is found in the fact that the process of nitrification, however actively it may be going on, is immediately stopped when chloroform-vapor is introduced, the effect being precisely the same as that seen when chloroform-vapor comes in contact with yeast. Again, these authors find that when nitrification has thus been stopped for several weeks, the addition of a small quantity of a nitrifying body will start the process again. They also find that the temperature of boiling water is sufficient to destroy all power of nitrification, and that soil which has once been heated to that point produces, in air free from germs, carbonic acid and ammonia, but no nitrates. If, however, this soil is moistened with water containing a little untreated soil, the production of nitric acid again commences. This new theory, as we learn from Nature, has been tested in England with results fully confirmatory of the views set forth by Schloesing and Müntz. Hence the evidence is very strong that the nitrates in soil owe their origin to oxidation brought about by living organisms.

 

How Ants distinguish Each Other.—Ants are eminently pugnacious, and opposing hosts belonging to the same species may any day in summer be seen waging internecine wars on one another. But how are they able to distinguish friend from foe in their tumultuous strife? Mr. McCook, member of the Academy of Natural Science of Philadelphia, has made sundry experiments which appear to show that difference of odor constitutes the means of discrimination. Of course, it is not possible to demonstrate this hypothesis directly by showing the existence, either of distinct odors, or of different intensity of odor, in opposing hosts. But, if we introduce into the scene of conflict some strong foreign odor which shall obliterate the odors peculiar to the two groups of combatants, we may deprive them of the power of telling friend from foe, and make them live together in harmony as one community. Such was the idea which occurred to Mr. McCook. He collected a number of combatants, and placed them, friend and foeman, together in a glass jar upon some soil. The battle was continued, and when it was again at its height a pellet of paper saturated with cologne-water was introduced into the jar. The effect was instantaneous. The ants showed no signs of pain, displeasure, or intoxication; indeed, some ran freely over the paper. But in a very few seconds the combatants had unclasped mandibles, released their hold of enemies' legs, antennæ, and bodies, and after a momentary confusion began to burrow galleries in the earth with the utmost harmony. The quondam foes dwelt together for several days in unity and fraternity, amicably feeding, burrowing, and building. Another experiment was as follows: A large number of warring ants were placed in a box partly filled with soil, and communicating by a glass tube with a smaller box. The larger box was about ten inches long and eight inches in depth and width; both boxes had sliding glass covers. Cologne was introduced as before into that end of the box in which the comba-