Page:Popular Science Monthly Volume 15.djvu/437

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Pathology. By J. N. De Hart, M.D. From the "Chicago Medical Journal and Examiner." Pp. 12.

On a Mode of measuring the Velocity of Sound in Wood. By M. C. Ihlseng, Ph.D. From the "American Journal of Science and Arts." Pp. 8.

A New Form of Compass-Clinometer. By I C. Russell. From "Annals of the New York Academy of Sciences." Pp. 2.

In the Matter of Certain Badly Treated Mollusks. By R. E. C. Stearns. Pp. 10.


Well-Water and Typhoid Fever.—In the summer of 1878 some forty persons in Rochester, whose supply of drinking-water was derived from a certain well, were taken sick with typhoid fever and other zymotic diseases. The health officer had the well closed, so that the people had to get water from other sources. Their recovery was rapid from that moment. A request was then addressed to all the physicians in the city to report the names and residences of all persons sick with typhoid fever. About fifty cases having been reported, health inspectors were sent to the various localities, who inquired into their sanitary conditions, the distance of cesspools, sewers, and privy-vaults from the wells; also whether the patients drank well-water either at their homes or at their places of business. Samples of water were taken from the wells, and submitted for analysis to Dr. Lattimore, Professor of Chemistry in the University of Rochester. The result of the inquiries was to show that, of the whole number of cases of typhoid reported, all but two had followed from the use of well-water; the exceptional cases arose from ill-ventilated apartments in close proximity to foul water-closets. It was also ascertained that a very large number of the wells in the city were situated within an average distance of less than thirty feet from cesspools and privy-vaults, while a great many were distant from them not over ten feet! In Professor Lattimore's report occurs one passage which must be quoted in extenso, namely, the one in which he remarks on the significance of the presence of common salt in well-water: "I would direct your special attention to the second column" [of his table showing the amount of solid matters in the water], "which shows the number of grains of common salt per gallon of water. No single indication is of so great sanitary importance in judging of the purity or impurity, and consequently of the safety or danger, of any water. How a substance, which is in itself not only harmless, but by most persons considered indispensable as an article of diet, becomes to the sanitarian a signal of danger in well-water, will be easily rendered apparent. No mineral substance is perhaps so universally diffused as common salt. It exists in the air, hence in all rain-water; in all soils, hence in all well or spring-water, though often in quantities too minute to be weighed upon the chemist's balance, as is the case in the Hemlock Lake water of this city. Salt being remarkably soluble, it is constantly being washed out of the soil into the streams, and ultimately carried down to its great reservoir, the ocean. We may, therefore, expect to find salt present in all ordinary well-water. What might fairly be considered as the average proportion for uncontaminated well-water in Rochester can be only estimated, but it certainly can not be large. Rivers may derive large quantities of salt from the drainage of manufacturing establishments upon their banks, but wells are not usually thus affected. Therefore, whenever, in well-water, it rises above a very few grains per gallon, it becomes certain that it comes from some other source than the soil. What is that source? A moment's reflection will convince any one that nearly all the salt used for domestic purposes escapes by the way of two channels—the water-closet and the house-drain. Therefore, we should expect, what is always found on examination to be true, that whatever sewage may or may not contain, it always contains salt."

Improved Diaphragm for the Phonograph.—Messrs. Preece and Stroh exhibited at a recent meeting of the London Royal Society a new form of diaphragm, which intensifies the loudness and removes some of the imperfections of the present disk of the phonograph. They had sought for a diaphragm which should give all the finest shades of sonorous vibrations, and, after trying many substances, a stretched membrane of thin India-rubber, rendered rigid