BANGKOK, which is the capital of Siam, was until quite recently built on piles and floating pontoons at the edges of canals and rivers, which, like the canals of Venice, were used for purposes of transport. To meet medern demands, however, and increased trade; roads have been built across the waterways, and the people now live chiefly in brick houses. Nevertheless the city is still impregnated with the romance of its past and the. mysterious charm of the East. which will be described at first hand this afternoon by Mr. Sargent. a great traveller, who has broadcast from Manchester several times before.