MECHANICS AND USEFUL ARTS. 105 



with a comiDlete set of "Wier's Pneumatic Signals," such as we 

 believe are in use on several of the Cunard steamers. The uses 

 to which this excellent apjiaratus is put are as numerous as they 

 are effectual. The apparatus is rather complicated in its details, 

 but simple enough in the principles on Avhich it works. By press- 

 ing down a lever on a series of chambers of compressed air, the 

 air from the latter is forced along a very small leaden pipe, pro- 

 ducing instantaneously at the distant end some mechanical effect, 

 — either ringing a bell, or moving a hand, or lifting up a small 

 flap, under which is written the signal meant to be observed. 

 On the Great Eastern there were, 1. An apparatus at botli ends 

 of the ship for communicating various messages to both screw 

 and paddle engines ; 2. An apparatus at each ot the 3 cable tanks 

 for signalling to screw and paddle, to stop and reverse, in case of a 

 hitch or foul-tlake in the tank ; 3. An apparatus connected, by means 

 of cams, with the shafts of the screw and paddle engines, register- 

 ing the revolutions of the same on a clock i^hiced in the engineer's 

 ofiice ; and, 4. A communication was placed between the bows and 

 the steering-wheel, to be used in case picking up should become 

 necessary. Connected with some of the apparatus was also a tell- 

 tale, which by an automatic action would indicate whether the 

 order sent had been obeyed or not. 



We have made a rough calculation of the cargo of the ship, in- 

 cluding her engines and boilers, when she left Portland, and be- 

 lieve the following to be a very near approximation ; it is cer- 

 tainly not over the mark : Cable, 5,520 tons ; cable-tanks and 

 water, 400 tons ; timber-shorings for tanks, 500 tons ; paying-out 

 and picking-up machinery, 120 tons ; ship's stores, 250 tons ; coals, 

 6,400 tons ; engines and boilers, 3,500 tons ; total, 16,690 tons. 

 Iler draft at starting was about 34 feet aft, and 28 feet forward. 

 This, of course, decreased as the cable \vas paid out, until, at 

 the end of the voyage, it was only about 25 feet aft, and 23 for- 

 ward. 



The arrangements made for the electrical testing of the cable 

 during submersion Avere, with one or two slight exceptions, 

 identically the same as in 1866. Their most interesting feature 

 is the keeping up of a constant test on ship and shore for insula- 

 tion, by a plan devised by Mr. Willoughby Smith in 1865, at the 

 sahie time allowing of tests for the continuity of the conductor, 

 and free communication between ship and shore to be kept up 

 without in any way interfering with the insulation test. By this 

 means, should a " fault "pass overboard into the sea, it is de- 

 tected at once, and the paying-out may be stopped before any 

 considerable length of the cable has been allowed to run out. 

 The advantage of this system over the old is apparent from the 

 fact, that formerly it was possible for 3 or 4 miles of cable to 

 run out between the occurrence of the fault and its detection ; 

 whereas now, except under very peculiar circumstances, with- 

 in two or 3 minutes after a "fault " passes overboard, it can be 

 detected, and the signal given to stop the ship. 



To give our readers some idea as to how a fault is detected, we 

 may (for this purpose only) compare the cable to a long pipe 



