able to the place in which it is designed to be put; one end of this tube is closed so as to present a rounded end, the form, however, not being deemed essential. The contrary end which forms the stay is turned conical at the point A, and is made to fit steam-tight into a corresponding conical hole in the interior of the furnace, either above or in the vicinity of the fire. After passing through the interior sheet of furnace, this tube is prolonged until it reaches the interior side of the external sheet of the boiler or fire box. Directly opposite this tube a hole is bored through the exterior plate to allow a bolt to pass through, so as to draw the tube tight into the conical hole, thereby connecting the inner and outer surface of fire box, and making a secure stay. Free circulation is made into the interior of this stay by two or more holes made through the portion of the tube in the water side, which permits free ingress of water and egress of steam in the direction of the arrows. The object in making the stay in this form is to secure the very efficient fire surface surrounding the part which extends into the fire box, and at the same time to make a secure stay removable at pleasure without difficulty by simply unscrewing the bolt b, a matter of much importance in boiler repairs. The use of such a stay enables the boiler to be more thoroughly cleaned by taking them out occasionally at the points where mud or other matter is most likely to collect. It will be seen that the tubular stay above described does not differ so far as it is used for increasing fire surface from the "teats," well known and long used, the improvement consisting only in the mode of putting them in, so as to make them act as a stay.

Locomotive Boilers.-Chapter the second. Sheet No. 2, figures 1, 2, and 3, show a boiler as at present used for locomotives, with certain additions for increasing the fire surface in the fire box. These additions consist in using the tubular stay wherever it is practicable, which has been alluded to in the description of Marine Boiler, and in placing a series of tubes filled with water across the fire box above the fire, and disposed in the manner shown in figures 1, 2, and 3, sheet No. 2. A series of screw plugs opposite each tube will enable them to be cleaned or taken out, if necessary. These tubes may be placed in the intermediate space between the present stays. The ordinary stays may be removed, and the new arrangement of tubular stay used between each of these cross tubes, and at any other parts of the fire box, either above or around the fire, where it may be deemed necessary. This arrangement of cross tubes may be applied, as well as the tubular stay, to any locomotive boiler now in use, thereby increasing the fire surface to a very considerable extent at the part where it is most efficient.

These improvements may also be with equal advantage applied to marine or other boilers, at any parts of the fire box or flues where it would be advisable to increase the fire surface; and it is so intended to apply them to any boilers now in use, or which may be hereafter made, upon the principle now generally in use. Sheet No. 3, figures 1, 2, and 3, show an arrangement somewhat similar to the mode of constructing marine boilers as previously described. In this case also, the external form of locomotive boiler is precisely similar to those generally in use; the variations being in the mode of getting fire surface in the interior of the boiler and fire box. The fire box is again extended forward, as in

the instance of the marine boiler, cylindrical in form, as shown in section figure 3, until it reaches within such distance of the tube sheet at the smoke box, в, as may be deemed most desirable. A series of tubes, D, D, D, D, figures 2 and 4, containing water leading from the back water space, F, figures 2 and 4, to the front water space, E. These tubes are

so disposed as to let the flame and combustible gases from the furnace, A, pass between and around them in their journey forward to the end of the internal cylinder, which, after reaching the heat that may still remain unabsorbed, passes out through the tubes, c, c, c, c, figures 2 and 4, which run through the water space, F, F, into the smoke chamber, B, and up the chimney in the direction of the arrows. For the purpose of supporting the tubes, D, D, D, D, it is intended, if necessary, to connect each row vertically as shown in figures 1 and 2, sheet 3, with a small pipe or pipes connected with the water space, surrounding the interior cylinder, thereby adding to the means of circulation, and at the same time supporting the longitudinal tubes. By experiment, it is found that these tubes, D, D, D, D, may in most cases, be made so short that no stay or support will be needed, whilst at the same time, a sufficiency of surface can be brought in contact with the fire to effectually take up all the heat that may be generated. The faint lines in figure 3, sheet 3, show the arrangement of short flues leading through the water space, F, F, figure 2 and 4, into the smoke chamber, B. For sustaining a more perfect combustion of the gases that pass from the fire, holes are made at G, G, G, G, figures 2 and 4, sheet 3, so as to let in at pleasure, a certain amount of pure air, which will become partially heated in being allowed to circulate between the sheet iron jacket and the boiler, before entering the tubes, G, G, G, G, G. Another method for heating the fresh air before entering the cavity of the boiler, and applicable to this boiler, will be hereafter described. Sheet 4 shows an arrangement of locomotive boiler, somewhat different from the one last described; this boiler has the same arrangement of cross tubes in the fire box above the fire, as is described in the specification of boiler, on sheet No. 2, and it is intended to have the tubular stays in the same manner as the boiler just alluded to. It has the middle or waist part of the boiler between the smoke box and fire box made square, with the corners slightly rounded, as shown in section, figure 3, sheet 4. The fire box is extended forward, also of square form, with regular water space surrounding it within; it reaches within a short distance of the tube sheet, at the smoke chamber. Instead of the horizontal tubes filled with water, as in two of the former descriptions, the interior chamber forward of the fire box is filled with vertical tubes containing water so arranged as to allow the flame from the fire to pass in between and amongst them, until it reaches the forward end, when it passes off into the smoke chamber through a series of tubes surrounded with water in the same manner as described in, and shown on, sheet No. 3, fig. 5, in section. The arrangement of vertical tubes, figure 6, sheet 4, shows an arrangement of this boiler, wherein the tubes leading into the smoke chamber are dispensed with, the smoke being carried off through the curved flue, A, into the smoke chamber. If it is required, the square part of the prolonged fire box may be carried entirely into the smoke chamber, and the entire intermediate space filled with the vertical or cros