All About Engines

2Ö2 Fif. 147.—Belpaire firebox All About Engines fire tubes ; and though experiments in this direc- tion have been made they have not yet been adopted on such a scale as to justify their inclusion in this book. Mr. G. J. Churchward, of the G.W.R., secured an increase in the size of the boiler by making it slightly conical, with the smaller end towards the front (see Fig. 145). This form has several advantages. In the first place, the greater volume of water is at the hottest end, and as a large firebox can be used, the heating surface is also increased. The steam dome is done away with, and there is less priming. More- over, the surging backwards and for- wards, when the en- its speed, is to some gine slows down or increases extent prevented, and there is less danger, therefore, of the crown of the firebox being uncovered. In this engine, and also in the engines of the Midland, London and North Western, Great Central, Great Eastern, Lancashire and Yorkshire, and North