Page:Popular Science Monthly Volume 14.djvu/135

Rh. He noticed that this line of distribution lies within the belt of the north trade-winds, and conjectured the existence of some connection between the two facts. Probability was given to the conjecture by the migratory habits of this spider in the early stages of its growth. The young spider emits from the spinnerets fine threads in sufficient bulk to overcome the specific gravity of the body, and it is borne through the air like a balloon. We some time ago gave an account of Mr. McCook's observations on ballooning spiders. Having found this spider in localities lying in the track of the northern trades, Mr. McCook made an investigation to determine whether the species is distributed along the entire track, and also whether it is to be found in the track of the southern trades. The result is exhibited by the author in a map which shows the existence of Sarotes venatorius in both belts of the trades, from the east coast of America, across this continent, the Pacific, and the whole Eastern Continent, to the west coast of Africa, thus girdling the globe, with the exception of 54° of longitude corresponding to the width of the Atlantic Ocean. The inference is that the distribution of this spider has been accomplished by means of the trade-winds.

The Growth of Mushrooms.—It is generally supposed that mushrooms grow only in the night, but those who have watched them have observed that their growth is nearly equal day and night. A correspondent writes that not long since a flower-pot was filled with dirt from the street, a plant was placed therein and it grew rapidly. In ten days a small mushroom made its appearance, but in a few hours it toppled over and perished. On the following day a larger one of different species was discovered peeping through the soil, and in the morning it was just above the surface. Before nine o'clock at night it attained its full height, nearly four inches, although it was in the sun several hours, and gradually expanded its acorn-head into a hollow cone which united with the hollow stem at the interior of the apex. Its inner surface was lined and evenly shirred with a black, velvety substance which made a fine contrast with the milk-white, cobweb-like substance of the outer surface. During the day and night the head was transformed into an umbrella-like cap, which collapsed and died on the fourth day. Others of different species, made their appearance at different times, showing that the streets of a city as well as the soil of the country are filled with spores of these seedless and flowerless plants ready to show themselves whenever the conditions of germination are favorable. They do not propagate by seeds—they have none—they propagate by spores, microscopically small, which are driven hither and thither by winds and lodged in various places, and when they receive the requisite amount of moisture and heat they germinate and grow to perfection, whether it be day or night.

Mercurial Deposit on Animal Teeth.—On the teeth of a sheep said to have been poisoned by the herbage growing in the neighborhood of a certain silver-mine in Mexico, Mr. E. Goldsmith, of the Academy of Natural Sciences of Philadelphia, noticed a peculiar deposit of tartar, which was supposed to consist of silver amalgam. Upon examination this tartar was found to constitute a thin scale covering the teeth to the depth of about 0.2 millimetre. Viewed under a lens of moderate power, the deposit seemed to have been built up gradually from within. Its lustre was truly metallic. Heated on platinum-foil it became black, showing the presence of organic matter. Heated in a tube closed on one end, at first a gray cloud arose, then water and an oily matter deposited themselves on the upper or cooler end of the tube; lower down near the now carbonized test a metallic layer was recognized with the aid of the lens. The powdered substance being mixed with carbonate of soda, and treated in the same way, the result did not differ. If melted on coal with the addition of carbonate of soda, there was obtained a white enamel, but no metal whatever. In nitric acid the tartar was soluble as long as the solution was concentrated; if diluted with water, a turbidity, caused by the separation of an organic matter, was formed. This organic matter was soluble in caustic ammonia, and from this ammoniacal solution it was again precipitable by nitric acid; the precipitate was flocculent, it carbonized when heated, and left no