Bahama Islands and the West Indies are of a rather coarse quality. The finest sponges come from the Mediterranean and the Red Sea. Sponges of good quality are found in Florida waters, the best variety, sheeps-wool, selling for $2 to $5 per pound. Sponge-fishing has there become an important industry, employing nearly 200 small vessels, with crews numbering more than 2,500 persons. When a vessel reaches the grounds, the men go out in pairs in rowboats, one man leaning over and scanning the sea-bottom with a water-glass. When a sponge is seen, it is secured with a kind of steel fork on a long, slender pole. The flesh is removed, sometimes by imbedding in the sand, and the skeleton is left. They are then soaked in water, and afterward squeezed and dried in the air. See Hyatt's Commercial and Other Sponges.
Spontaneous Combustion, or burning without the application of fire, sometimes occurs in mineral and other substances. Charcoal, if saturated with oil, may become so heated as to burn, and coals containing iron pyrites, when wet, will catch fire. Phosphorus, when dry, ignites easily, and has been known to melt and burn in a room where the temperature was only 70°, so that in hot weather a fire may be started by large packages of matches. Hay, cotton, tow, flax, rags, straw, leaves, if collected in large quantities, when damp undergo fermentation, which gives off sometimes enough heat to burn. The cotton-rags and waste used in wiping oiled machinery and lamps have probably started many unexplained fires. Spontaneous combustion of the human body has been thought to occur in a number of cases, usually where the individual was an habitual drinker, but is now considered doubtful. Liebig says a dead body filled with alcohol may burn of itself, but not a living one, in which the blood is circulating. See Letters on Chemistry by Liebig.
Spontaneous Genera′tion of Life, the doctrine that life in some form is developed from non-living matter. The ancients believed that frogs and eels sprang from mud, that insects were generated in dew, that decaying meat bred maggots, that the appearance of other forms of life was to be accounted for by spontaneous generation from lifeless matter. This belief was quite general until the 17th century, when the Italian, Francesco Redi, made experiments to test the truth of it. He placed bits of meat in open jars, and others in jars that were covered by fine gauze, and watched for the development of maggots. The blow-flies visited the uncovered meat, but were prevented from reaching the other. Of course, maggots hatched from the eggs, but did not appear in the protected meat, and, by this simple experiment, he proved that maggots did not arise spontaneously from the meat. This was about 1660. He made further experiments and reached the conclusion, not as a matter of opinion, but as a result of experiment, that life arises only from antecedent life and does not develop spontaneously.
This position was quite generally accepted for larger animals, but with the introduction of the microscope, a new world of extremely minute living beings was made known, and doubts began to be entertained that those minute beings must always have parents like themselves. It is a well-known fact that fluids, like clear mutton-broth or water, in which any vegetable or animal substance has been soaked, will, if allowed to stand, soon become teeming with microscopic life. The possibility of this life arising by spontaneous generation formed a new phase of the question. Needham and Buffon attempted to put the matter to test by boiling infusions, to kill all germs that might exist in them, and corking them tightly. In course of time these fluids became cloudy and were overrun with microscopic life. But about 1775 a priest of the period named Spallanzani, showed that their experiments had not been conducted with sufficient care. He boiled infusions for three quarters of an hour in flasks, and, while the fluid was still boiling, heated the necks of the flasks and, drawing them into a fine point, he closed them by heat. No microscopic life appeared in the flask treated in this way, and the conclusion was drawn that spontaneous generation of life was disproved.
About this time oxygen was discovered and shown to be necessary to all forms of life. This brought a new point of view, and objection was made to Spallanzani's form of experiments on the score that oxygen was excluded by sealing the necks of the flasks. In order to test this objection, Schulze and Schwann in 1836 took up the question again and devised a means of admitting oxygen into the flasks containing fluids that had been boiled. The necks of the flasks were drawn out long, and convoluted, and left open at the ends. In some cases the inlet was heated and air drawn in. In other cases the air was passed through bulbs containing chemicals that did not alter the oxygen. It was soon discovered that a plug of cotton-wool in the necks of the flasks would act as a filter. It permits the air to pass through and arrests all floating particles and, therefore, does not allow dust or germs to pass through with the air. A flask, or test-tube, is partly filled with an organic infusion; the latter is boiled and, while boiling, a plug of cotton-wool is pushed into the mouth of the vessel. On cooling, the air passes through this plug, but the smallest solid particles are caught in the meshes of the cotton-wool. Organic fluids treated
