One of the best known water-tube boilers on land in England and America is the Babcock & Wilcox, one of which was fitted and tried in the s.s. ‘Nero’ in 1893. In this boiler (Figs. 72 and 73) the generating tubes are fitted between a number of headers, or narrow sinuous vertical water chambers of square section, each pair of which (one at the front and one at the back) is united by tubes inclined at an angle of about 1 in 4. The gases from the fire pass around the tubes and thence to the funnel 

Niclausse boiler. 

This is illustrated in Figs. 74 and 75, and has been fitted in a considerable number of vessels in foreign navies, and consists of a series of slightly inclined double tubes, one inside the other, attached at the front end in such a manner that the colder water flows down the inside tube, and returns to the front between the two tubes when heated by the action of the fire and hot gases on the larger outside tube.