138 ANNUAL OF SCIENTIFIC DISCOVERY. 



ON THE MECHANICAL PROPERTIES OF THE ATLANTIC TELEGRAPH 



CABLE. 



At the British Association, 1864, Mr. Fairbairn, the celebrated 

 English engineer and scientist, read the following paper on the above 

 subject : 



It appears that the Atlantic Telegraph Company, considering it 

 essential to the public interest that the second attempt to submerge a 

 telegraph cable across the Atlantic should not be left to chance, and 

 that a close and searching investigation should be entered upon, and 

 that nothing should be left undone that could be accomplished to 

 insure success, sought the advice of a committee composed of men of 

 eminence and experience in the various branches of science and en- 

 gineering involved in such an undertaking to advise the Company in 

 the selection of a cable. For the satisfactory attainment of this 

 object it was considered necessary, in the first place, To determine 

 by direct experiment the mechanical properties of cables submitted 

 for submergence in deep water ; 2d, To- ascertain the chemical prop- 

 erties of the insulator, and the best means to be adopted for the 

 preservation and duration of the cable ; and 3d, To determine the 

 electrical properties and conditions of the cable when immersed, 

 under pressure, at great- depths. On the author of the paper de- 

 volved the. duty of undertaking the first division of the inquiry, viz : 

 to determine, by actual experiment, the strengths, combinations, 

 forms, and conditions of every cable considered of suitable strength 

 and proportion to cross the Atlantic. A laborious series of experi- 

 ments was instituted, and, in order to attain accuracy as regards the 

 resisting powers of each cable to a tensile strain, they were broken 

 by dead weights, suspended from a crab or crane, by which they could 

 be raised or lowered at pleasure. The weights were laid on one cwt. 

 at a time, and the elongations were carefully taken and recorded in 

 the table as each alternate cwt. was placed on the scale until it 

 was broken. By this process we were enabled to ascertain with 



freat exactitude the amount of elongation in seven ft. six in. 

 he result of the investigation was, the selection of the cable of 

 Messi's. Glass & Elliott, which stood highest in order of strength. 

 In this inquiry, upwards of 40 specimens of cables have been tested 

 in their finished state, and this might have been sufficient for the 

 Committee to determine the best description of cable ; it was, how- 

 ever, deemed advisable to investigate still further, not only the cable 

 as a cable, but to test experimentally each separate part, in order 

 that every security should be afforded -as to the strength and quality 

 of the material to be employed in the construction. With regard to 

 the covering wires, constituting the principal strength of the cable, 

 j\ir. Fairbairn finds that with proper care in the selection of the ma- 

 terial in the first instance, a judicious system of manipulation in the 

 second, and a rigid system of inspection of the manufacture, a wire 

 of homogeneous iron '095 inches diameter can be made of strength 



t to sustain from 900 to 1,000 Ibs., with an elongation of 'OOG8, 

 or j- 8 - - parts of an inch per unit of length. This description of- 

 iron appears to be the mo>t suitable fur the Atlantic cable, as it com- 

 bines strength with ductility, and may be produced at a comparatively 



