A New York City Fish.
It seems strange that in the great city of New York should be found a fish which is unlike all others, yet such is the case. In the lake in Central Park is found a pearl roach which differs so much from the pearl roach of various waters that it has been given a new place as a subspecies. Instead of being called simply Abramis chrysoleucas, it is called Abramis chrysoleucas roseus. However, the fish is much more beautiful than its name, and indeed is one of the handsomest in the aquarium at the Battery. Its body is silvery gray which has a trick of sparkling like mica as the light falls on it at different angles. Its fins are brilliant vermilion.
The Pearl Roach.
Now you will ask the question, “How came this fish in Central Park and not in other lakes and in streams?” and the answer of the scientists is, “We do not know.”
The theories are that these fish are descendants of the common pearl roach which may have been in the park lake always or placed there many years ago and have since changed color and shape because of especially good food-supply thrown to them by visitors to the park, or that some one had European roaches in an aquarium, and tiring of them, liberated them in the lake. They therefore may be a product of especial food or of change of climate or environment. Anyhow, they are a puzzle to the scientists and a delight to the eye of the nature-lover.
Spring Migration of Birds.
Cold as is February, it is the beginning of various life-interests of spring and summer. Among the birds to arrive, beginning at the middle of the month, are the woodcock, purple grackle, rusty blackbird, red-winged blackbird, phœbes, and several others. The list varies in different places. Many four-footed animals resume activity at this season, and even some reptiles crawl out on warmest days.
What is Thunder.
Dear St. Nicholas: I have seen so many things clearly explained in your Nature and Science for Young Folks that thought I would ask you a question I am anxious to learn. What causes the thunder?
Your constant reader,
Thunder is a noise. Noises are caused by waves of air striking the ear and passing into it and producing au effect upon the eardrum or tympanum, Waves of air are caused by some disturbance in the atmosphere, just as water waves are produced when a stone is thrown into the water.
Just as the waves beat upon the shore, so sound waves beat upon the ear. The impulse in both instances depends upon the kind of waves. The higher the wave the stronger the effect upon the resistance offered.
What can make a sound wave? To answer this let us observe the strings of a violin, When the string is bowed it moves back and forth rapidly, This motion causes the air to be compressed and sets up a wave which reaches the ear.
As these movements are regular and rapid we call the noise music. If the noise is irregular we simply call it noise.
So thunder is a noise. The cause is the passage of an electric spark from cloud to cloud or from cloud to the earth.
Thunder is produced on a small scale when we discharge a Leyden jar or turn the Holtz machine. The tiny noise we hear when we comb our hair with a rubber comb is miniature thunder.
Just how lightning causes thunder is a harder