BEFORE proceeding to give tabulated computations of the fire and flue surface of boilers, the performance of the different varieties with respect to consumption of fuel, and such other particulars relative to their performance as will be a guide to the engineer and show forth the best methods of construction, we think it expedient to give drawings of some of the boilers of which these particulars are to be determined, both to render our tabulated results clearer than they could otherwise be, and to furnish the engineer with examples to avoid or imitate. These delineations are all made to a scale, and on the more important of them the sizes are also marked; so that these wood-cuts may serve all the purposes of working drawingshalf an inch either in excess or defect in the length of a boiler being a thing of no importance. Subjoined are given two scales, the one or the Fig. 40.

No.!

expense of a great agitation of the water, which might occasion priming: but we have not been able to learn that these evils have arisen to any inconvenient extent in practice; and we find manufacturers and others persevering in the use of this species of boiler, which says much in its behalf. Fig. 43.

in consequence of being of French origin. This boiler is a good deal used in Lancashire, and is spoken of highly. We think it more conducive to accomplish perfect combustion than any boiler with which we are acquainted, on account of the interposition of an arch of brick between the furnace and the boiler bottom,-two tubes, connected to the boiler by means of necks, being the whole heating surface to be found in the furnace. The smoke, it will be observed, first passes to the end of the furnace beneath the brick arch, and then, rising up, comes forward to the front of the boiler in the space left between the brick arch and the boiler bottom, after which it passes, by the plan of a split, along the boiler sides to the chimney. The anticipation, looking to the peculiar construction of this plan of boiler, would naturally be, that the tubes situated above the fire would be liable to burn out from the accumulation of depositure in them, and that the steam could only ascend to the water surface with great difficulty, and at the

Scale one third inch=1 foot TRANSVERSE SECTION.

Fig. 43. is a transverse section of a 30-horse-power waggon boiler of the kind employed by Messrs. Boulton and Watt. This boiler will serve as a type of its class. We shall hereafter give the length, breadth, height, and surface for the different powers.

Fig. 44. represents the boilers erected by Messrs. Maudslay and Field at the London terminus of the Blackwall Railway. One set of them is on the Cornish plan, and the other of the ordinary marine construction; and with the same amount of surface, and all other circumstances as nearly as possible the same, the Cornish have been found to be the least effectual at the pressure at which these boilers are worked.

Fig. 45.

of the engines or the number of the boilers to the drawings, as all this information will be given in a more commodious form in the tables we intend to furnish.

Figs. 49. and 50. represent a Yankee boiler, which will be looked upon as a sort of phenomenon in this country. The vessel in which this boiler is applied is said to run 150 miles in about 9 hours. The plates are " thick; rivets, " diameter, and the pressure of the steam is 50 lbs. ! Figs. 51, 52, 53, 54, 55, 56, are different views of the boilers of the

Scale one-fifth inch=1 foot.

LAND BOILER BY MESSRS, CAIRD AND CO. Longitudinal Section.

Figs. 45. and 46. represent a land boiler of a very good description constructed by Messrs. Caird and Co. for a blast engine of small size. This kind of boiler is common enough; but it has generally only one tube for conducting the smoke through the boiler, instead of the number here represented.

Figs. 47. and 48. represent the boiler introduced by Messrs. Caird into some iron tug-boats made by them. Cylinder, 32 inches in diameter, length of stroke, 3 ft. 6 inches. We shall not, in general, append the size

Scale one fifth inch=1 foot.

AND BOILER BY MESSRS. CAIRD AND Co. Transverse Section..