Page:Popular Science Monthly Volume 46.djvu/589

Rh eddies or give the wind an upward direction. To be subject to transportation by the atmosphere, rock materials must be finely comminuted; and the author has ascertained by experimeut that the average largest diameter of quartz particles that can be sustained in the air by ordinary strong winds is about one tenth of a millimetre. But the capacity of the air for transporting particles below this size is very great, and is estimated to be per cubic foot at an average velocity of five miles an hour, one thousandth that of water. The whole atmosphere over the Mississippi Valley, if the wind blows ten times as fast as the river runs, may transport one thous.and times as much dust. Atmospheric currents being loaded, for the most part, only to the extent of an insignificant fraction of their capacity, their sediments will be better sorted—the fine material will be more completely separated from the coarse—than deposits from water currents, which are more often loaded to their full capacity. That deposition of dust will take place where wind is caused to slacken its speed is self-evident, and is observed every day in the accumulation of dust on the windward side of a closely built-up street.

Boarding Schools and Infection.—The Agency of Boarding Schools in Disseminating Infectious Diseases was the subject of a paper by Dr. Clement Dukes at the Congress of the British Institute of Public Health. The author charges boarding schools with not having exercised sufficient care in the protection of society against sanitary detriment from influences they might control. The conditions of boarding schools, with their regular vacations and occasional leaves of absences, are such that there is almost a perpetual to-and-fro communication between them and the home. Then, when pupils become ill they are sent home, if practicable; and when general illness breaks out in the school, those who have as yet shown no symptoms of it, or only the beginnings of them, are sent home These pupils, possibly bearing the seeds of infection, travel in the public conveyances in contact with unsuspecting passengers, or to be followed by such, to whom disease may be communicated. The spread of infectious dis. eases by boarding schools is admitted to be, unfortunately, to a certain extent, necessary by virtue of the existing system and the susceptibility of the pupils. Beyond this, such diseases are often disseminated ignorantly and thoughtlessly by the operation of motives in which such result is not contemplated, or wantonly. As remedies for the evil the author suggests bills of health to be given by parents on sending their children to school and by teachers on sending pupils home; and that schools should make adequate provision for the treatment of illness of their pupils and for the retention of all patients till they are absolutely free from infection.

Mistaken Diagnoses.—Common Diseases Mistaken or Mistreated is the subject of an address recently delivered before a medical society by Dr. J. F. Goodhart, of Guy's Hospital. It concerns the diagnosis and treatment in every-day practice of cases which practitioners must see regularly, which are yet frequently mistaken and mistreated. Infantile scurvy, for instance, is a very common complaint, but is often not recognized, and allowed to pass as rickets or rheumatism, or injury, or temper. Another disease which, although very common, varies much in severity and in the mode in which the pain manifests itself, is angina pectoris. It is often mistaken for indigestion, neuralgia, rheumatism, flatulence, etc., and fatal results have often followed from the wrong treatment having been adopted. Other instances of error occur in the confusion of the passage of urates with that of uric acid, in the adoption of a rigid form of dieting to get uric acid out of the system, when it is the individual that should be treated, and his malady, individualized in him, through him; and in the treatment of renal colic and chlorosis. The author emphasizes the fact that many of the methods and aims of medicine are faulty by reason of the ready assumption that their bases are unassailable; that men are constantly driven back upon their own experience, and compelled not to accept it but to question it.

Tests for Old Plumbing.—The tests usually applied in inspecting old plumbing work, as named by William Paul Gebhard, are the peppermint test, the smoke test, and sometimes an air-pressure test. The water test is not practically applicable to plumbing work in actual use, because it necessitates the