106 ANNUAL OF SCIENTIFIC DISCOVERT. 



scaled up at one end, into whicli water is being forced. As long 

 as the pipe remains perfect, only a certain amount of water can 

 be jnit into it, according to its capacity, and once filled, there is 

 no tlow of water; but if, when the pipe is full, a small hole be 

 made in it, the water will of course rush out at once, indicating 

 the existence of the hole by causing a fresh fiow of water into the 

 pipe. Now, the cable is always kept chargcnl with electricit}' up 

 to its full capacity, — or, in other words, till it can take no more, — 

 and as long as it remains perfect there is practically no currinit 

 llowing from the battery into it; but immediately on the devel- 

 opment of a fault, or communication between the conductor of 

 the cable and the earth, a portion of the charge escaping through 

 the fault causes a fresh supply of electricity to fiow from the bat- 

 tery. By having a delicate instrument fixed between the battery 

 and the cal)le, this increased flow is at once made apparent. 



As to the track of the cable, it seems from the soundings taken 

 that the bottom is composed, the greater part of the distance, of 

 the fine mud usually called " ooze," consisting of very minute 

 shells, — so minute that without a microscope the shape is not dis- 

 cernible. This "ooze" constitutes the very best bed for a sub- 

 marine cable. In fact, judging from the experience of 18G6, the 

 cable lies in it as securely and as free from harm as when coiled 

 in the tanks at the manufactory; and if picking up should become 

 necessary, the softness of the "ooze" renders the grappling of 

 the cable comparatively easy. 



Tiie position of the present cable has one advantage over that 

 of the English cables, namely, that it has been kept carefully oflf 

 the Newfoundland IJanks, and will therefore not be liable to the 

 breakage by iceberges which have already caused such expense 

 and trouble to the English company. Tiie cable is conducted 

 several miles to the south of the "Great Newfoundland Bank," 

 and then proceeds in a north-westerly direction to the western 

 side of St. Pierre Island, passing along a deep gullv between the 

 "Green Bank" and the " St. Pierre Bank." The' length of the 

 course selected is about 2,330 knots, and the amount of cable paid 

 out 2,580 knots, — making about 10 per cent, allowance for 

 "slack," or spare cable paid out to cover the inequalities of the- 

 bottom, and to allow of i)icking up, should such become necessary. 

 Without takinjr notice of the 300 knots from the Brest shore, and 

 the 500 knots from Newfoundland, where the water is shallow, 

 the depth varies from 1,700 to 2,700 fathoms, the deepest part l)e- 

 ing sitr.ated in about 45° north, and longitude 43° west. — Cham- 

 Iters' Journal. 



THE FRENCH ATLANTIC CABLE. 



Various plans of testing submarine cable during paying out 

 have been tried, but all have their disadvantages. None, liow- 

 ever, are in any way to be comjiared to the plan now adopted. 

 This is the invention of Mr. Willoughby Smith, a gentleman of 

 very great experience, the electrician engaged during the paying 



