Charles William Pasley to Faraday   17 October 1859

High Elms, | Hampton Court, S.W. | Monday Morning the 17th October 1859

My dear Sir,

I should like to have a few minutes conversation with you on a subject very interesting to me, and of some importance to the Service of the Country.

It relates to Pontoons, which have always been my hobby horse, as you may perhaps recollect. I proposed decked copper canoes shaped like boats and the late General Blanshard¹ also of the Engineers proposed tin cylinders with paraboloidal ends. The midsections of the two are as below

When a heavy weight such as a Gun presses them down to within 4 inches of the surface of the water, Pasley’s pontoon requires more than a Ton of additional weight to press it down to the water’s edge, whilst Blanshard’s from having so little capacity in the upper part would be in great danger of sinking, and after each heavy gun whether drawn by men or horses passes over any one cylinder, the moment that this is relieved of the weight there is a violent rebound of the superstructure in rear of the gun that flies up as if it were forced by a powerful spring. Thus a very dangerous oscillation or rather undulation of the roadway is occasioned, that has a tendency to frighten horses, and was the cause of an accident in the Pontoon Bridge formed over the Thames at Runnymede, when a 9 Pounder Gun of a field battery went over into the river with Drivers and Sappers employed as Pontoneers on the same side, because they cannot stand in safety on a cylindrical surface, so that they were obliged to jump in to save themselves. On this occasion 2 out of 6 horses (those in the shafts) were drowned the others saved by cutting the traces. The Men some of whom could not swim escaped. I should have mentioned before, that both sorts were sent out to Bombay for trial, by order of the Court of Directors of the East India Company in 1826 and were tried in a creek subject to the action of the Tides for a short time, in two or three years after which, Blanshards tin cylinders having become a mass of rust and dust were thrown away and mine were adopted as the standard Pontoon for India and are still established as such.

I now wish to bring them forward again to supersed the tin cylinders, and my object is to consult you about the properties of copper, iron and tin.- The latter has been proved to be destructible even in the brackish water of the Medway to guard against which, the men are obliged to carry the cylinders down to the river and gently deposit them on the surface of the water, instead of launching them like boats, and in landing them, on leaving off work, they lift them out with equal care, and in the meantime my Exercise has been adopted by Blanshard whilst his are afloat. Part of the men having mud boots for wading into the river manage this business of the launching and landing. The others carry up or down the bank which may be steep. In fact whenever the paint is rubbed off the thin iron follows it and holes are eaten through it by the action of the water. Even on grass or on the smoothest fine sand, the same effect takes place, so that they must never touch the ground².

If you take a walk this morning will you do me the favor to call, or I will call on you at one o clock P.M. which is our luncheon time, for which as you know I do not care, or only employ a quarter of an hour at most[.]

I remain, My dear Sir | Yours very faithfully | C.W. Pasley