Knight's American mechanical dictionary : a description of tools, instruments, machines, processes and engineering, history of inventions, general technological vocabulary ; and digest of mechanical appliances in science and the arts . lowest average he gives is that of Cairo in Egypt, three days of thunder per annum. That ofParis and most of the European cities is about fifteenilays. He estimates the da)s of thunder at NewYork to be about the same. Fig. 2954 exhibits some of the numerous varietyof rods forwhich patents have been secured in theUnited States. (I has a series of points fo
Knight's American mechanical dictionary : a description of tools, instruments, machines, processes and engineering, history of inventions, general technological vocabulary ; and digest of mechanical appliances in science and the arts . lowest average he gives is that of Cairo in Egypt, three days of thunder per annum. That ofParis and most of the European cities is about fifteenilays. He estimates the da)s of thunder at NewYork to be about the same. Fig. 2954 exhibits some of the numerous varietyof rods forwhich patents have been secured in theUnited States. (I has a series of points formed of spiral coils com-bined with a tuliular portion, forming the tip. Theconductor is a flat strip. b, a jointeil tubular conductor for It isdivided at the head of the lower mast, a branchleading down the shrouds on either side to the wa-ter. c, an iron rod tipped with copper, the point ofwhich is gilded. d has a central copper slip inclosed between ironside-pieces ; the points of connection have inter-posed zinc LIGHTNING-ROD. 1318 LIGHT-SHIP. e. The iron rod is grooved to receive a copperslij). The joints are secured by screw-threaded wasli-ers. f. The point is Iormed witli two opposite wings. Fig. Ligktnijlg Rods^ Points, and Attachments. q. The rod is composed of a .sinj^le strip of copperwound spirally .so as to form a tube. h is composed of several strands of wire laid to-gether so as to foini a rope, and having several tips. i. The point is funned of three or more metalsinclosed one within the otliei-, the most fusible out-side. j is an insulating attaclnnmit with additional con-ductor points at the coupling of Iod-sections. k. A copper cable, composed of a central wire io])eand two exterior strands laid up in o)iposite direc-tions. / comprises two or more copper-wire ropes inter-twined with an ecjual number of iron rods. VI. A series of metallic stii|is, forming a tube, arejoined together, 11. A metallic stiip is doubled up or fcorrugated,so
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