This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1880 edition. Excerpt: ...This fact has led to the practice, now generally followed in the streets of London and elsewhere, of as far as possible hermetically sealing the joint boxes and excluding the...
Paperback: 158 pages
Publisher: RareBooksClub.com (September 13, 2013)
Product Dimensions: 7.4 x 0.3 x 9.7 inches
Format: PDF ePub Text djvu book
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er agent in the destruction of underground wires is lightning, or the induced currents caused by lightning. The connecting wires between the Central Telegraph Station in London and the various railway termini are laid underground, and, when a current caused by lightning passes through the underground wires to find "earth", if a weak spot in the percha comes in its path, it escapes through it, developing a fault and causing leakage. To remedy this, lightning protectors are now being fixed at the junction of the underground and overground wires. Another enemy to the preservation of gutta percha exists in vermin: rats indulge freely in gutta percha, and are evidently only deterred from knawing through it by shocks received on reaching the conducting wire. Mice have contributed their share of interruptions to gutta percha covered wires. But the peculiar cause of deterioration in gutta percha that I want to bring before you to-night, is one due to the existence of an extremely minute insect--an animal so small that it easily escapes the naked eye. It happened a short time ago that simultaneously underground wires in different parts of the country showed novel signs of decay similar to each other. Not being satisfied with the reason attributed by the local officers, I resolved to examine the wires in situ for myself. I used my microscope to examine the dirt surrounding the wires, and soon perceived that an almost invisible white speck was really an insect of a very lively disposition, for as soon as it alighted on one place it jumped off to another. The...