Page:Collier's New Encyclopedia v. 03.djvu/129

LEFT COMPRESSED AIR LOCOMOTIVE 95 COMSTOCK LODE more easily transported a distance than can steam, which loses some of its power through condensation. COMPRESSED AIR LOCOMOTIVE, a locomotive in which the power is fur- nished by air under pressure. These loco- motives resemble a steam locomotive, ex- cept that in place of the steam generat- ing apparatus they carry tanks of air under pressure, which tanks have to be recharged at a pumping station. The principal use is in chemical works, ex- plosive plants, textile works, mines, lum- ber mills, cotton presses; in fact, any- where that every precaution against fire has to be taken. The mining locomotive may be taken as a typical example of a compressed air locomotive. The air is carried in one or two steel tanks, the capacity of which is determined by the use: load, length of haul, etc., which is to be made of the locomotive. These tanks are placed in the same position that the boiler would occupy on a steam loco- motive, and the air is conducted to an auxiliary tank, the pressure in which can be controlled, from which tank it is conducted to the engine cylinders. The flow of the air is controlled by a reduc- ing and a stop valve. For a number of years an attempt was made to operate street railway mo- tor cars with air. In New York City several cross-town lines were equipped with cars carrying tanks imder the floor of the car or under the seats. In most cases modern engineering uses some form of electric vehicle such as the storage battery locomotive, in place of the compressed air locomotive. COMPRESSED AIR TREATMENT, a system of treatment in which use is made of air under pressure. The treat- ment is used for tuberculosis, and in some forms for asthma and chronic bronchitis. There are two main methods of administering the treatment. In the first the patient is placed in an air-tight chamber, and the pressure of the air is increased. In this case the pressure on all parts of the body is the same, and is said to cause increased absorption of oxygen. In the second method, the pa- tient is placed in a cabinet, a tube which he places in his mouth being the only connection with the outside air, and the air pressure in the cabinet is reduced; thus the pressure on the lungs is greater than on any other part of the body, which may relieve collapse of the pul- monary vesicles. COMPTOMETER, a calculating ma- chine that is operated by a key-board in the manner of a typewriter. It consists of a box entirely inclosing the mecha- nism, with the operating keys projecting from the box in typewriter fashion. Along the front edge of the box are open- ings in which numbers appear, and above these openings are pointers. The keys are 72 in number, and each has two fig- ures painted on it. One is a large black figure and the other a small red one. The black ones indicate the keys that are to be struck in addition and multi- plication, and the red ones those to be struck in division and subtraction. The successful operation of the machine de- pends upon the practice of the operator in the same manner that efficiency of the typewriter depends upon the amount of practice that the operator has had. No proficiency in mathematics is required on the part of the operator; anyone skilled in handling the keys can rattle away at the comptometer as confidently as if he were writing letters on a type- writer, and all the time be adding up large sums or dividing millions by thou- sands without any of the laborious thinking usually required of the mathe- matician, the bookkeeper and the ac- countant. COMPULSORY MILITARY SERV- ICE. See Military Organization, United States. COMSTOCK, GEORGE CARY, an American astronomer, bom in Madison, Wise, in 1855. He graduated from the University of Michigan in 1877. After studying law he was admitted to the bar, but never engaged in active practice. He was assistant engineer of the United States Lake Survey from 1874 to 1878. He was later assistant engineer on the improvement of the Mississippi river; assistant astronomer at the Washburn Observatory; and computer in the Nau- tical Almanac Office. From 1885 to 1887 he was professor of mathematics and as- tronomy at the Ohio State University. From the latter year he was full pro- fessor and director of the Washburn Ob- servatory. In 1906 he was created dean of the Graduate School of the University of Wisconsin. He was a member of many learned societies. His writings in- clude "Method of Least Squares" (1890) ; "Text-Book of Astronomy" (1900) ; "Field Astronomy for Engineers" (1902) ; and "The Summer Line as an Aid to Navigation" (1919). COMSTOCK LODE, a large and ex- tremely rich metallic lode in the W. part of Nevada, on the E. slope of the Vir- ginia Mountains. To it belong the Big Bonanza and other mines, which have yielded gold and silver to the value of over $300,000,000.