

IUVINC-1 



lHVIXii-BELL. 



Abo, by hauling in the rope while the weight was at the bottom, the 

 pereoos in the bell might lower themselves at pleasure. Another 

 improvement oouuted in the addition of > horuooUl partition iur 

 the top of the bell, which divided off* chamber Out might, by suitable 

 opening! anil valves, be ailed either with water, or with air from the 

 lower part of the bell ; *o a* to altar the specific gravity of the whole 

 machine, and thereby to oauee it to ascend or descend at pleasure. 

 The bell ws* supplied with air by an apparatus reaembling that uf Dr. 

 Halley; and ropes, stretched acroa* the Ml, were uaed instead of seats 

 and platforms for atanding on. By theae arrangements the peraona in 

 the diving bell were enabled, in caee of accident, to raise themaelvei to 

 the aurfaoe without any assistance from above ; and it waa rendered ao 

 perfectly manageable, that it might be removed to a considerable 

 ^fri-Tw^ from the jwint at which it descended ; iU outward motion, 

 and ita return to the veaael for the purpose of being hauled up, being 

 stated by a longboat, which carried the aignal-linea and the tackle 

 for working the air-barrel*. 



Though not in chronological order, it may be well here to allude to 

 an improvement upon Spalding's apparatus, contrived by Mr. John 

 Farcy, junior, and described by him in the article ' Diviug-Bell,' in 

 Brewvter'a ' Edinburgh Encyclopedia.' He propoaes to make the 

 upper chamber of the diving-bell very strong and air-tight, without 

 any openings for the admission of water. In the partition are fixed 

 two forcing-pump*, by which a portion of air should be forced into the 

 upper chamber, whenever, during a pause in the descent, the lower 

 chamber, or the cavity of the bell, is replenished with air. By this 

 means the upper chamber U made a reservoir of condensed air, from 

 which the bell may be replenished with air when it is desired to increase 

 ita buoyancy by forcing out the water from the lower part. In like 

 manner, the buoyancy of the bell can be at any time diminished by 

 pumping some of the air from it into the upper chamber, whereby the 

 water wdl be allowed to enter to a greater height ; and, as this is 

 H^***** without wasting the air, there is no danger of diminishing the 

 buoyancy of the machine to a degree which would prevent it from 

 ruing in case the suspending rope or chain should break. Mr. Farey 

 recommends the form of the fnutuni of an elliptic cone, for diving- 

 bells intended for descending to wrecks ; the dimensions being, for a 

 bell to hold two persons, 6 feet by 4 at the base, 3 feet 6 inches by 

 2 feet 6 inches at the top, and 6 feet 6 inches high. He also suggests 

 the use of a pressure-gauge in the bell, to show the divers what depth 

 they have descended to ; and of a compass to enable them to ascertain 

 and give proper signals respecting the direction in which the bell 

 should be moved. These signals are given by snatching a rope, wl.i.-h 

 may be marked in the same manner as a deep-sea lead-line [SouxmNosJ, 

 so that, after giving a signal to raiae or lower the bell, the divt-i m .\ . 

 by hauling in a certain quantity of the signal-line, intimate the height 

 to which the bell should be moved. Farey recommends that the men 

 be attached by ropes to the bell, so that in case of falling, they may 

 not sink ; and that, in case of being obliged to leave a wreck to which 

 it is intended again to dive, the balance-weight may be left at the 

 bottom, with a buoy attached to the upper end of ita rope, so that the 

 right point for descending may be found without difficulty. 



The credit of having been the first to apply the diving-bell in aid of 

 civil engineering operations is usually attributed to Smcatou , who used 

 it in 177!) in repairing the foundations of Uexham Bridge. Thf 

 Report in which he recommended its adoption is a very interesting 

 document, as it affords a familiar explanation of the principle of the 

 diving-bell. It is dated September 10,1778; and is printed in the 

 collected edition of his Reports,' vol. iii., p. 279. The bell uaed on 

 this occasion was an oblong box of wood, 4 feet high, 2 wide, and 

 34 long ; and it was supplied with air by a pump fixed on the top. 

 The river being shallow, the bell was not covered with water ; but in 

 1788 the diving-bell was used in a much more important work, Rams- 

 gate harbour, by the same engineer. Being here used at a consider- 

 able depth, an apparatus was employed for forcing in a supply of air 

 through a flexible pipe, by means of a forcing-pump in a boat. The 

 bell used in this work was of cast-iron, similar in form to that em- 

 ployed at Uexham, but 44 feet high, 44 long, and 3 wide. IU weight 

 was fifty cwt., and the thickness was so adjusted that it would, without 

 the addition of any weights, sink in the proper position. In levelling 

 foundations under water by this machine, the surface of the water at the 

 bottom of the bell formed a convenient and unerring level to work to ; 

 and in this, as well as in the subsequent operation of building, every 

 necessary motion was given to the bell by the tackle by which it wait 

 suspended; signals being made from below by striking one, two, 

 three, or more blows upon the side of the bell with a hammer. 



Since the time of Smeaton the diving-bell has been frequently, and 

 with great advantage, employed in submarine works ; sometimes in 

 situations in which it would have been impossible to construct a 

 coffer-dam, or to perform the required operations by any other means. 

 The diving-bells uaed in such works are usually formed on the 

 model of that made for the works at Uamagate harbour ; but the 

 mode of auspension differs according to circumstances. The bell 

 may be suspended over the side or end of a venocl ; through an 

 opening in the centre of a barge ; from frame-work resting n,,,,,, 

 two barges, placed |jorallel with each other, but at such a diKtanco 

 .i.'.irt as to allow the bell to descend between them, or ii..:n ., 

 Bcoflbliling supported by piles. In operations at the harbour of 



Howth, near Dublin, the late Mr. Rennie used a diving-bell suspended 

 from a kind of railway soaflblding like that described under SCAFFOLD- 

 Uio, M used in erecting Urge stone buildings ; two carriages being 

 uaed upon the scaffold, one to lower the stones, and the oil 

 manage the bell. By the apparatus described as above, aided by 

 ropes attached to the atones, and managed by the men in the bell, the 

 submarine masonry could be executed with great facility. Uf the use 

 of this important machine in recovering property from wrecks, the 

 operations upon that of the Royal George afford a familiar example. 

 According to the ' Annual Register,' vol. lix., p. 42, this wreck was first 

 sun-eyed by the diving-bell on the 24th of May, 1817. Smeaton's 

 method i .-applying air to the bell is that moat commonly employed ; 

 but that of Halley may, in some cases, have the advantage. 



The diving-bell, with some slight modifications in the details of the 

 pumps, and of the hoisting and lowering apparatus, continues to be 

 used in the execution of hydraulic masonry of a difficult and delicate 

 nature ; and occasionally, as in the execution of the harbour of refuge 

 of Dover, for the purpose of raising the huge muneos of masonry in the 

 jetties carried out into deep water. 



In whatever way a diving-bell may be mounted, it is essential that 

 it should descend very gradually, and that its descent should be per- 

 fectly under control In 1838, Mr. Richard Jones, who had been 

 placed in a very perilous situation by the failure of the crab by which a 

 diving-bell in which he was descending was being lowered, was rewarded 

 by the Society of Arts for a contrivance to prevent the occurrence of 

 such an accident. His improved crab has a brake, regulated by the 

 centrifugal motion of two balls, like the governor of a steam-engine ; 

 so that, while the crab revolves slowly, and therefore allows the bell 

 to descend gradually, the brake may not be called into action ; but if 

 it should, from any cause, be overpowered by the weight of the bell, 

 so as to run down with dangerous velocity, the separation of the balls 

 should disengage the brake, and thereby stop the motion of the crab. 

 The machine is described and represented in detail in vol. Iii., p. 7-. 

 Ac. of the Society's ' Transactions.' 



Of late years a system, originally suggested by Coulomb in 1788, of 

 executing masonry, or other hydraulic works, at great depths from the 

 -n i' if,-. li:w Ixwn umd with considerable 8iiccess at the Rochester and 

 the Saltash bridges. In these cases the foundations were laid without 

 coffer-dams, by means of air-tight chambers in which the workmen 

 laboured in an atmosphere of condensed air. An account of the 

 machinery uaed at Rochester bridge was printed by Mr. Hughes, who 

 conducted the works; and a description of an analogous operation 

 <1 at Croissac, in France, has been given by M. de la Gournerie 

 in the ' Annales des Fonts et Chaussees ' for 1818. The cylinders 

 used by Dr. Potts have a distant connection with this class of opera- 

 tions, but it will be more convenient to notice the whole subject more 

 in detail under the article FOUNDATION. 



Many plans have been proposed for enabling a man to walk beneath 

 the surface of water, or to dive in such a manner as to assist in the 

 raising of anchors, or the recovery of property from wrecks, by means 

 of waterproof coverings for the head and upper part of the body 

 strong vessels in which every part but the arms should be encased ; a 

 supply of air being either transmitted from above by a flexible pipe, or 

 contained in the cavities of the protecting armour. Such apparatus 

 may be conveniently used at small depths ; but at any considerable 

 depth they are both dangerous and inconvenient, because the strength 

 necessary to enable them to bear the pressure of the water is incom- 

 pitil/li- with the flexibility essential to the free use of the limbs. 

 Dr. Halley alludes, in hia paper on the diving-bell, to some coutn 

 of this kind ; and in a subsequent paper (' Phil. Trans.,' No. 868, vol. 

 xxxi., p. 177) he describes an apparatus of his own invention, by which 

 a man might leave the diving-bell, and walk about at the bottom of 

 the sea ; his head being covered by a heavy leaden cap like a small 

 diving-bell, supplied with air by a flexible tube extending from the 

 large bell. The diver was to coil this tube round hia arm, and unwind 

 it as he left the bell, and to use it as a clue to direct him to the bell in 

 returning. This pipe was formed of leather soaked in oil and hot wax, 

 and was held open by a spiral coil of brass wire, its internal diameter 

 being about one-sixth of an inch. The pipe waa then covered with 

 several thicknesses of gut, and over all with leather. The modern 

 invention of waterproof India-rubber cloth, which baa been applied in 

 various ways to diving apparatus, affords great facilities for the manu- 

 facture of water-tight tubes for such a purpose. So long as the helmet 

 was above the level of the water in the bell, it would be kept full of 

 air ; and in case of having to stoop below that level, as in getting out 

 of or into the bell, the diver had only to clo.- y which the 



air in the helmet was prevented from returning into the bell. The 

 front of the helmet was glazed ; and the diver, who was cloth' 

 thick woollen dress, fitting close to the body, to diminish tin- c 

 the coldness of the water, was enabled to walk by means of a weighted 

 girdle and weighted clogs. Aquatic armour, whether supplied \\ it h air 

 from above, or carrying a store in its cavities sufficient to lost for the 

 ii'i.. the diver intends to remain submerged, has been brought eo little 

 into use that it U needless to devote the space required for a minute 

 description. The apparatus of M . i liich was first described 



in a pamphlet published at Breslau in 171)8, has been fully explained 

 t in Tilloch's ' Philosophical Magazine' (vol. iii., pp. 59 and 171), and in 

 iii.niy other English works; and a more recent contrivance of similar 



