Page:Popular Science Monthly Volume 38.djvu/734

716 to a pressure of forty-five pounds above the atmosphere is delivered into pipes which are laid like gas-pipes over four miles of streets. The works had only left the hands of the contractors, when there were forty customers for air-power, some of them at a distance of a mile and three quarters from the compressing station. The loss of power by friction in the pipes is so light that no ordinary gauge will show it. The engines of the consumers vary in size from half a horse-power up to fifty horse-power. Under the system of Hughes and Lancaster, by which compressed air may be applied to tramways, a pipe is laid in the street for the supply of compressed air to the cars, which carry the machinery for propulsion. Any gradient which a locomotive can mount can be ascended by the cars, and fresh supplies of air can be taken in without stopping the cars.

Petroleum as an Explosive.—Experiments by Peter T. Austen exhibit petroleum as an explosive of the dangerous class. It evolves inflammable gases at ordinary temperatures, and some of them are not liquefied by a considerable reduction of the temperature. The author applying a match to a flask containing crude petroleum at zero Fahrenheit, the flask was filled with a blue flame. Since the evolution of gas is increased by shaking the oil, an inflammable gas must accumulate in the vacant parts of car-tanks, in a condition more or less favorable to explosion. If the gas in contact with the petroleum becomes ignited, the oil will, in most cases, take fire unless the body of the liquid is very cold; and the danger increases as the temperature. The behavior of a tank of petroleum under pressure has not been much studied; but all know how tinder may be ignited in a "fire syringe"—an effect of simple compression. The lubricating oil of the piston also takes fire at a temperature of about 300°. The volatile gases of petroleum may be ignited at a lower temperature. If the mixture of air and vapor over petroleum is compressed to one fourth its volume, the temperature will be raised to 429° from zero, and to 499° from 70° Fahr. It follows, therefore, that if an oiltank filled or partly filled with such a mixture is suddenly compressed in such a way as greatly to reduce its volume, the gas, and probably the oil, will be ignited by the compression. This might happen in r. case of telescoping or of a fall of the tank. If a tank nearly filled with oil were suddenly compressed, the resistance offered by the liquid would heat it sufficiently to cause an evolution of its lighter hydrocarbons in sufficient quantity to create a dangerous pressure within the tank. This might happen when, the car being stopped in a collision, the oil is suddenly hurled against the front end of the tank. The author concludes that precautions against explosion are necessary in the transportation of crude petroleum.

Alcohol as a Cause of Disease.—Dr. Lewis D. Mason, of the Inebriate Asylum, Fort Ilamilton, N. Y., discussing The Etiology of Dipsomania and the Heredity of Alcoholic Inebriety, determines as facts that alcoholism in progenitors will produce physical and mental degradation in their descendants, with the disorders that arise from a defective nerve organization; and all grades of mental weakening, from slight enfeeblement of intellect to insanity and complete idiocy; and that the laws regulating these changes are similar to those that govern congenital degenerative changes from other causes. The offspring of the confirmed drunkard will inherit either the original vice or "some of its countless Protean transformations." In another paper—on Pathological Changes in Chronic Alcoholism—Dr. Mason exhibits alcohol as modifying the serum and the anatomical elements of the blood, besides being an irritant and directly producing modification and degeneration of tissue, and therefore as being most evidently a disease-producing agent. Contrasting the little progress that has been made in the study of the pathology of chronic alcoholism and of the diseases incident to alcoholism with the great advance that has been achieved in knowledge of microbic diseases, he adds: "Alcohol has not any microbe, but the grand total of its mortality will exceed the combined effect of all the bacteria that have ever passed the microscopic field or developed in the culture-tube of the bacteriologist." The subject is now, however, beginning to receive some of the attention it deserves.