KMffOOK. 



IH 



o the Umbw. by riband, formed of young tree. .pUt to two 

 oMitudinally and tied by willow twig* 



A eaak bridge i. ometime. formed in the following manner : A 

 certain number of caak. are placed aide by ride, ao a. to form a sort 

 fluting pir, having their axe. in horizontal poajtion. ; the cak. are 

 tdto two gunwale timber., a. they are called, which extend along 

 the upper aide of the pier at the extremities of the caak. ; two of these 

 pier, are placed at an interval of about 10 feet from ** *}er, and 

 {key are Snnectod together by the baulks which .upport th. platform^ 

 A. many of the*) rait, are prepared a* may- be neoeary, they are 

 rowrfto their place, in the line, d the bridge i formed in the atme 

 manner a. the pontoon bridge above described. 



When the formation of a bridge extending over a river from on. 

 bank to another become, impoenble, numerou. expedienU are had 

 recoune to for conveying troops acron by mean, of what are called 

 SwngW moving bridge.? We learn from Arrian that the army of 

 Sexinder paed the Indu. by mean, of boata and rafta of timber, the 

 latter being wipportod on bag. made of Ain and inflated with air ; and 



Vaimilar rninner the infantry of Hannibal is said by Livy to have 

 crosaed the Rhine. In India, at the prewrat time, the passage of nven 

 iorten effected by mean, of baskeVboate, which formed of split 

 bamboo, and coveVed with half -dreawl hide.. Each veel id to 

 be capable of containing about 80 men. 



In 1811. Captain Squire., of the Engineers, formed a bridge over i 

 Guadiana by&dng trwtle-piers in the shallow part, of the river and 

 mooring boita inQie middle ; but just u the bridge wa, fimshed the 

 river .welled and carried away tile trertle*. The boate were then 

 converted into flying bridge., to convey over the cavalry and artiUery , 

 and a slight narrow bridge was made for the infantry with pontoon, 

 and caaks the Utter being taken from the neighbouring village.. 



Captain Fowke, R.E., ha. lately invented a pontoon which appear, 

 likely to Kiperaede thoae now in uae. It is a boat pontoon, the 



in hi. own word. (' Royal 



Section of Pontoon. 



Stern of Pontoon. 



Pontoon folded. 



boat* confuting of canva. on w<xlrn frame.. The accompanying 

 drawing, will explain their form. The advantage, claimed for them 



by their inventor an bert explained 

 Engineer Corp. Paper.,' voL YI: 



1. The buoyancy i. nearly double. 



8. The weight u lea. than half. 



S. The length on the line of march U leaf than half. 



4. The firat ooat i. only two-fifth*. 



5. The bulk, when packed, i. only one-nventh. 



The height of the roadway abov. the water U increased. 



7. The .ability U greater, and the tendency of the bridge to Mod- 

 late from aid. to aid* M avoided ; thi. motion U oauaed by th. end. of 

 the pontoon, being alternately immeraed or plunged downward., and 

 will, tattrit peril*,, alway. increan a. the vertical Motion of the 

 pontoon approaches the form of the aolid of least reiuOnce ; and as a 

 flat surface offer, conriderably more reawUnce than one with a circular 

 or curved Motion, it follow, that, independently of all consul 

 buoyancy, the canva. pontoon will excel in .lability from thu cauae. 



8. The liability to damage from .hot i. diminished, a. a grape .hot 

 or musket ball, which would make a serious wound in metal, will 

 merely perforate th canva. with a very small n.im.l li..lf. 



9 In the caws of a pontoon grounding while under a heavy weight, 

 where the metol one would be put quite hor. de combat, the worst 

 that would be likely to happen to a canva. one would be the fracture 

 of a frame or two, which would not oocaaion a leak, and could eaaily 

 and quickly be repaired. 



10. The pontoon can be bailed out eaaily, even while in bridge ; and 

 this operation i. no longer dependent on the small pumps, alway. ao 

 slow in action, and ao likely to choke and get out of order. 



11. The weight of every individual piece of the bridge is diminished, 

 as well as the number of piece., and the superstructure i. simplified ; 

 in forming a bridge, one operation, that of Uahing on the saddle, (often 

 a difficult one), U entirely avoided. 



12 It would appear from the considerations in the last paragraph 

 that each waggon load could be formed into bridge with at least equal 

 celerity us one load of the service equipment, and, if so, there will be a 

 saving of nearly half the time in forming a bridge, eight waggon load, 

 of the canvas pontoon forming as much bridge as fifteen of the 

 service one. 



18. The durability i greater : one of the greatert advantage, which 

 the canvas pontoon seem, to possea* over that now in uae (a. far as 

 can be judged at present) is that while its liability to injury i 

 diminished, in point of durability it appears to be very superior to the 

 latter pontoon, whether on the march, in water, or in store. Jolting 

 on the march, or rolling over uneven ground, or down a stony beach, 

 is almost certain to sOrt one or more joint, of the metal pontoon, 

 slightly perhaps, but sufficiently to admit a small quantity of water, 

 so small as to be disregarded ; on being brought out of the water the 

 pontoon is then stored with its inside and all its delicate framework 

 quite wet, and the process of corrosion thus commenced, tends still 

 further to weaken the joints and render them even more liable to such 

 accidents ; and this account* for the fact that few, if any, of the present 

 pontoon, have ever gone through a summer's practice at Chatham 

 without having to be put at least once into the hands of the tinman 

 for repair. The canvas pontoon, on the contrary, from the elastic and 

 yielding nature of it* materials, is less liable to injury on shore ; running 

 it on piles or rocks has absolutely no permanent effect on it, for a like 

 reason ; and on the march it is enclosed in its own defensive armour of 

 hoops, which effectually protect, it from injury. As an example of the 

 durability of such a construction, may be cited the case of the fishing- 

 boats on the west coast of Galway, which are made of canvas sir. 

 over a wooden skeleton, without any external protection, and wliiuh 

 stand all weather out at sea for many years. As to durability in store, 

 I have had an opportunity of very carefully examining eight canvas 

 pontoons in store at Chatham; of these one was constructed in the 

 1 Kinning of 1863, two more in the course of the same year, and three 

 ;irly part of 1855; and although they have all been out re- 

 peatedly, and the latter frequently, I think it will lie found that they 

 are not deteriorated in any respect : the oldest of all would l>e j 

 the better of a coat of boiled oil, but nothing more is necessary for any 

 of them. 



14. The canva. pontoon could without much difficulty be made in 

 the field, .uch material, as hoops of casks, canvas, poles, and oil, bcinj- 

 almost always procurable; and one or more extra waggon, may be 

 attached to each bridge-trajn, carrying nine pontoons each, to be avail- 

 able in cane of emergency. 



15. A tingle pontoon can be used and pulled as a boat, for laying out 

 anchor., Ac!, and as it is stable in the water it may be pulled or poled 

 into la place in the bridge. 



Three pontoons, similar to the one described, have been constructed 

 at Chatham, and subjected to some severe test, as to buoyancy ; in 

 one InsOnce a heavy 82-pounder was put on a raft of two pontoons and 

 the load was increased by men and sandbags to 95 cwt, with which 

 load it was floated out into the Medway, and it bore it without any 

 apparent strain, and with considerable spare buoyancy. The only point 

 in which theK pontoon, appeared to be inferior to those in use was in 

 the single one of speed in rowing, the expression in the report bring 

 that they seemed to be too light to row well ; this appears to me to be 

 a matter of such small consideration that I should not have noticed it 

 but for an ida that seem, to prevail that the quicker a pontoon rows 



