An improvement in steam-boilers, best understood by reference to the ordinary vertical form, has been introduced by Mr. T. Moy, London. Here the flue is central, and, as shown in the accompanying illustration, is crossed by a number of horizontal water-tubes at different heights. The ends of these tubes are embraced, within the steam chamber, by annular troughs. At the top domed part of the boiler are two annular chambers, the outer one being intended to receive the water upon entry from the feed-pump, and to contain any sedimentary deposit which may be formed. The water next passes, by the pipe, a, in the figure, into the inner chamber, surrounding the end of the uptake flue, whence it flows through the pipe, b, down into the first of the annular troughs above mentioned, and afterward overflows these troughs in succession until it reaches the bottom. Mr. Moy claims to have secured by this means a boiler of quick steaming capacity, together with a reduction in the weight of metal, and considerable economy of fuel. By the arrangement of the water in a number of shallow layers a large steaming surface is obtained, and there is a good steam space rendered available round the troughs. The water also enters at a point where it may abstract as much heat as possible from the furnace gases before they escape; and by the separation of the top domed chamber from the rest of the boiler the operation of scaling and cleaning is facilitated. The arrangement is also adapted to horizontal and multitubular boilers, to be fired with solid, liquid, or gaseous fuel.