Thirty chapters on static electricity selected from the original manual of Static electricity in X-ray and therapeutic uses / by S.H. Monell.

  • Monell, S. H. (Samuel Howard), -1918.
Date:
1903
Catalogue details

Licence: Public Domain Mark

Credit: Thirty chapters on static electricity selected from the original manual of Static electricity in X-ray and therapeutic uses / by S.H. Monell. Source: Wellcome Collection.

Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.

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    tween the two is manifested in many ways. To make a direct test, put the poles one or two inches apart and start the machine into slow action. Watch the poles and the first spark will be seen to jump from one ball to the other. If this is detected by the eye it instantly shows that the pole from which the spark jumped was the positive. With the spark stream now in full and continuous action it will be seen to be a violet tint for nearly half its length at one end and bright at the other end. The violet tint shows the negative pole, the white light shows the positive pole. Also pull the rods slowly apart until the brush discharge be- tween them splits. From the positive pole there will be a single straight handle from the brass ball to the brush, while the negative end will have no defined and single handle. Draw the poles still farther apart until the brush divides. With a good machine, a dry room fairly darkened, and a high speed of the plates, the famous fox's tail will flare in splendid radi- ance between the poles. It never remains upon the negative. If none of these several steps of an ordinary test satisfy the beginner who has not yet acquired the confidence of experience, place the sliding poles about six inches apart or so that the dis- charge between them is a compact stream instead of a scattered brush. Ground the brass point electrode and put its point in the course of the spark stream at either pole. It is obvious that interference with a jet of water at its terminus will scatter but not abolish the jet, while interference at its source will deflect it or even stop it altogether. As the current passes from the positive to the negative the grounded electrode placed at the positive pole will completely abolish the spark stream by con- ducting it away. If the electrode interferes at the negative pole the spark stream will persist from its positive source and will be affected only at its terminus. With a small machine and a moderate current this latter test is easily made with a match held in the hand, as I have formerly