Page:EB1911 - Volume 22.djvu/82

Rh Continental armies had meanwhile constantly adhered. Captain Fowke, R.E, invented a folding open bateau, made of waterproof canvas attached to sliding ribs, so that for transport it could be collapsed like the bellows of an accordion and for use could be extended by a pair of stretchers. This was followed by the pontoon designed by Colonel Blood, R.E., an open bateau with decked ends and sides partly decked where the rowlock blocks were fixed. It consisted of six sets of framed ribs connected by a deep kelson, two side streaks, and three bottom streaks. The sides and bottom were of thin yellow pine with canvas secured to both surfaces by india-rubber solution, and coated outside with marine glue. The central interval between the pontoons in forming a bridge was invariably maintained at 1 5 ft.; for the support of the roadway five baulks were ordinarily employed, but nine for the passage of siege artillery and the heaviest loads; they fitted on to saddles resting on central saddle beams. The pontoons were not immersed to within 1 ft. of the tops of their “coamings” when carrying ordinary loads, as of infantry in marching order “in fours” crowded at a check, or the 16-pounder R.M.L. gun of position weighing 43 cwt.; nor were they immersed to within 6 in. when carrying extraordinary loads, such as disorganized infantry, or the 64-pounder R.M.L. gun weighing 98 cwt. In designing this pontoon the chief points attended to were—(1) improvement in power of support, (2) simplification in bridge construction, (3) reduction of weight in transport, and (4) adaptation for use singly as boats for ferrying purposes. One pontoon with the superstructure for a single bay constituted a load for one: waggon, with a total weight behind horses of about 40 cwt.

The following table (from Ency. Brit. 9th ed.) shows the powers of various pontoons in use by different nations in the past. Modern improvements are comparatively few. The “working power of support” has been calculated in most instances by deducting from the “available buoyancy” one-fourth for open and one-tenth for closed vessels:—

Pontoon Length

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Ft. Cub. Ft. ℔ ℔ ℔ ℔ Ft. ℔ ℔, Ft. 1 ℔ Gribeauval: open bateau, oak   36·3 593 45,044 8,044 37,000 27,750 22·8 1,215 840 15-6 35,568 Austrian: open, wooden, 1799 ... 27·0 354 22,123 3,332 18,791 14,093 16·6 849 560 11·4 18,924 Aust.-Birago: open, wooden; two pieces  28·0 303 18,907 3,249 15,658 II, '}'44 21-7 542 560 9-3 20, 18 I ,, three,,  39·4 445 27,791 3,384 23-907 17-930 21'7 327 560 9'3 20,131 ,, iron; two pieces  28·0 353  22,090 3,398 I§, g92,       'Egg ;O, I§ I ,, three 39·4 530 33-135 4, 01 2, 84 1 ' ' 0,1 1 French; open, wooden; reserve  30-9 325 20,286 3,608 16,678 12,509 19-7 635 560 10-5 20,685 advanced guard 19-7 156 9,734 1,506 8,228 6,171 16-4 376 560 ' '9-3 15,252 general ... 30-9 321 20,065 3,153 16,912 12,684 19-7 644 560 9-8 19,306 Prussian: open, wooden; open order, 23-7. 164 10,226 2,393 7,833 5,875 15-3 384 560 9-9 15,147 close order 23·7 164 10,226 2,213 8,013 6,010 11·2 535 560 9-9 11,088 iron; open order 24-7 214 13,385 2,209 11,176 8,382 15-3 561 560 9-9 15,147 close order 24-7 214* 13,385 2,029 11,356 8,517 11-2 759 560 9-9 11,088 Italian: open wooden;tone piece  233 17,660 3-,582 14,273       528 ,, two pieces .2 5 351320 1 2 301 4 1, ° ' 1 ,, modified; one piece .. 24-6 325 20,290 §, ;51.0I 16,889 12,669 23-0 551 560 9-8 22,540 ,, two pieces ... 49-2 649 40,580 4,489 36,091 27,068 23-0 1,178 560 9-8 22,540 Russian open, canvas on Q open order 21-0 209' 13,042 2,355 10,687 8,015 16-6 493 560 10-4 17,264 wooden framework; close order  2I'0 209 13,042 2,083 10,959 8,219 11-7 705 560 10-4 12,168 Belgian; open, iron; one piece   24-8 297 18,584 3,336 15,248 II,436 19-7 580 560 9-5 .18,715 1, ", two pieces . . 49- 595 37,168 4,548 32,620 24,465 19-7 1,244 560 9-5 18,715 American india-rubber, three; open order 20°C 130 8,125 1,980 6,145 5,530 I8°O 307 580 11-0 19,800 cylinders connected; close order 20-0 130 ' 8,125 1,824 6,301 5,761 14-7 393 560 11-0 18,370 English Pontoons.

Peninsular % open, tin; reserve   18-9 209 13,092 2,374 10,718 8,039 16-8,477 560 10-0 16,8OO equipment, ,,, advanced guard 15-1 120 7,520,1,654 5,866 4,400 14-0 314 560 9-0 12,600 Pasley: closed demi-canoe; copper   25-0 141 8,781 2,103 6,678 6,010 12-5 481 560 10-0 12,500 Blanshard: cylinder, tin; open order  22-5 109 6,785 1,600 5,185 4,667 12-5 373 560 10-0 12,500 close order   22-5 109 6,785 1,408 5,377 4,839 8-3 581 560 IO'O 8,300 light pattern  15-5 26 1,640 340 1,300 1,170 5-3 220 280 7-0 3,710 Fowkez open, collapsible, canvas; open order 22-0 134 8,460 1,246 7,214 5,411 10-0 541 560 10-0 10,000 Forbes: closed, spherangular, tin; open order 24-2 128 7,977 1,689 6,288 5,659 11-0 514 560 10-0 11,000 Blood: open, wooden; general ... 21-6 280 -17,500 2,300 15,200 13,350 15-0 890 560 10·0 15,000 In the English and French equipment the pontoons were originally made of two sizes, the smaller and lighter for the “advanced guard,” the larger and heavier for the “reserve;” in both equipments the same size pontoon-is now adopted for general requirements, the superstructure being strengthened when necessary or very heavy weights. The German army has an undivided galvanized iron pontoon, 24 ft. 6 in. long, handy as a boat, but of inadequate buoyancy for heavy traffic, with 'the result that the span has to be diminished and ipso facto the waterway obstructed. The Austrian and Italian - pontoons are made in three pieces, two with bows and a middle piece without; not less than two pieces are ordinarily employed, and the third is introduced when great supporting power is required, but in all cases a constant interval is maintained between the pontoons. On the other hand, in the greater number of pontoon equipments greater supporting power is obtained not by increasing the number of supports .but by diminishing the central interval between the pontoons. Within certain limits it does not matter whether the buoyancy is made up of a large number of small 0r'a - small number of large vessels, so long as the waterway is not unduly contracted and the obstruction offered to a swift current dangerously increased; but it is to, be remembered that pontoon bridges have failed as frequently from being washed away, as from insufficient buoyancy. In Austria efforts have been made to diminish the weight of the Birago equipment by the substitution of steel fori iron. The present pontoon, in three pieces, is of steel, and 39 ft. 4 in. long, like the old pattern.

In the British army Colonel Blood’s equipment was later modified by the introduction of a bipartite pontoon designed in 1889 by Lieut. Clauson, R.E. Each pontoon is carried on one waggon wit a bay of superstructure, and consists of two sections, a bow-piece and a stern-piece, connected together by easily manipulated couplings of phosphor bronze. Decks and “ coamings ” are dispensed with, and) the rowlock holes are sunk in a strong gunwale. The detachable saddle-beam, which receives the load on the centre of the thwarts, is made in sections, so as to form a continuous saddle of any length required. The baulks (or road-bearers) and chesses (or planks) remain unaltered, but chess-holders and chess-bearers are added for use in constructing light bridges for infantry in file. Inj this kind of bridge each pontoon section is used separately, with 'a roadway of chesses' placed longitudinally four abreast. In the normal or medium bridge two sections, and in heavy bridge three sections are joined together. The chief advantages of the