106 ANNUAL OF SCIENTIFIC DISCOVERY. 



sea bottom in a series of loops or " kinks ; " thus accounting for each 

 mile of cable not covering its allotted mile of sea. TJie vessels were, 

 therefore, compelled to remain anchored at the end of the submerged 

 wire until the deficit could be manufactured and forwarded. This was, 

 however, soon effected, and the connection between the two coasts 

 rendered firm and complete. The connections with the inland tele- 

 graphs of England and France were soon afterwards made ; and the line 

 is now in practical working order, messages having been transmitted 

 and returned from London to Paris in less than three minutes. 



The whole cost of the cable was about 15,000, and it is confidently 

 hoped that it will remain permanent and unaffected by the agitation 

 of the sea. A patent to obviate that difficulty has been secured in 

 England, by Mr. Dick, of Ayr. His process is to enclose the wire, pre- 

 viously encased in gutta percha, in a cast-iron envelope. This envelope 

 is made of perforated balls and perforated cylinders, threaded on the 

 cable in succession ; first a ball, next a cylinder, another ball, another 

 cylinder, and so on. Of course, the ends of these cylinders are so formed 

 as to fit the balls exactly, and the structure is a succession of knee- 

 joints, or rather a shark's back-bone. This arrangement claims to 

 produce an effective protection of the rope, with flexibility and cheap- 

 ness. 



The success of the telegraph between England and France has, to 

 some extent, revived the project of a trans-atlantic one between Europe 

 and the United States. The London Morning Post, in discussing the 

 subject, says that the only difficulty of the undertaking is to provide 

 the requisite funds. Making an estimate for a wire rope, one inch in 

 diameter, covered as usual, the cost would be 50 per mile, and the 

 nearest points of Europe and America being 2,000 miles apart, the 

 whole expense would not exceed $2,500,000. The importance of such 

 a work is not to be estimated by thousands of millions. 



APPLICATION OF THE ELECTRIC TELEGRAPH TO A NEW SYSTEM OF FIRE 



ALARMS. 



THE following is an account of the application of the electric tele- 

 graph to a new system of fire-alarms, first devised by Dr. William F. 

 Channing, of Boston, and recently carried out by the municipal 

 authorities of that city, under his direction. The application of the 

 telegraph to fire-alarms was first published by Dr. Channing in the 

 Boston Daily Advertiser, of June 3, 1845. In 1847-8, an attempt was 

 made to realize it in Boston ; but the experiments by the city were not 

 carried to the extent of erecting wires. In the month of March, 1851, 

 he presented a detailed plan to the city government of Boston, which 

 was adopted in June ; and an appropriation of $10,000 was made to 

 carry it into effect. An essential feature of the system is the employ- 

 ment of electricity, first, to signalize the existence of a fire to the cen- 

 tral office, and, second, by means of electro-magnetism, to produce 

 mechanical effects at the churches or other buildings containing alarm- 

 bells, so as to give a public alarm. Two separate circuits are employed 



