Page:Popular Science Monthly Volume 90.djvu/60

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��Popular Science Monthly

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��Testing two pieces of strap, one found at the scene of the murder, the other in a suspect's pocket

from an anaemic person. Often the field is narrowed down to one or two persons.

The chemists examined the scrapings from the murdered man's finger-nails. Under the microscope they found shreds of human hair and fine particles of blue cloth. The murdered man had worn a suit of dark gray. There was no trace of blue dye in it. Evidently, the cloth must have been torn from the coat of the murderer.

With the chemists' report before him, Inspector Faurot narrowed the search down to the mining engineer's two enemies. And the chemical and microscopic clues furnished by the Central Testing Labora- tory enabled him at once to charge the tubercular suspect with the crime.

But what of the strap? How did that figure in the case? Was it the same as the piece found in the suspect's coat pocket? To answer the question, comparative tests were carried out in the Central Testing Laboratory. Both pieces were stretched until they broke. Thus their tensile strength was determined. The readings of the machine were identical for both pieces.

When the suspect confessed, he said that he had opened the bundle of papers hoping to find an old mining report which he could use to make a favorable report on his mine. He had intended to forge the murdered man's signature.

��A Pneumatic Device for Destroying Devastating Animals

IT has been estimated by the Govern- ment that ten million dollars' worth of crops are annually destroyed by ground squirrels in the United States. Besides, these animals are said to transmit such diseases as the Bubonic plague. To make war upon them, therefore, an unusually handy and effective device has been in- vented by Irving D. Charlton and Professor W. T. Shaw, of the Department of Zoology, State College of Washington. It consists of a circular container which is filled with some poisonous liquid such as carbon bisulphide. A handle is geared to a suction fan in the device. As it is turned the fan causes a current of air to enter the opening formed by the inner wall of the circular container. The air current strikes against a perforated disk which is mounted on the fan-shaft and which rotates with it. The air is then deflected and flows towards the outer rim of the disk, some of it going through the perforations into the liquid in the container and some of it going through the wetted perforations nearer the top of the device. The air then proceeds along towards the fan, carrying some vaporized liquid with it. On reaching the fan the mixture of vaporized liquid and air is forced by the fan down the discharge pipe.

���The gas is forced through the pipe into the burrow and the animals therein are asphyxiated

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