Spons' Dictionary of Engineering, Civil, Mechanical, Military, and Naval Volume 2 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1870 Excerpt: ...leading to them. The wires on coming from the entrance of the gallery are passed up the face of the cliff, and are represented in Fig. 1167 by Nos. 2 and 4 wires. Nos. 2 and 4 wires lead to the charges below. Nos. 1 and 3 are connected with the five mines above through the interposition of the mercury cups. On the word to mahe recnly, Nos. 1 and 2 are attached to one pole of the battery, Nos. 3 and 4 being held one in each hand. On the word fire lower mines, No. 4 is connected to the other pole of the battery, and the lower mines explode. On the word fire upper mines, No. 3 is connected to same pole as No. 4, and the five upper ones explode. If instantaneous explosion of all mines be required, Nos. 3 and 4 should be previously tied together, and on touching the other pole of the battery all the mines would explode simultaneously. It was originally intended to have fired the large mines below simultaneously by one battery, arranging the conducting wires as shown in Fig. 1183, that is, the wire proceeding from the battery was to have been carried directly to, and connected with, the bursting charge of one of the lower mines; from this, again, a conducting wire proceeded to the bursting charge of the other, which again was connected by the same means with the other polo of the battery. The whole circuit by this arrangement would have been about 300 yds. Subsequent experiments have proved that it would have been successful. When the time fixed for the explosion drew near, doubts were expressed in influential quarters of the safety of the plan, and as, from want of time, there was no means of proving its practicability by a sufficient number of experiments to remove all doubts, it was thought advisable to adopt the old method of firing each lower mine by a separ...