y and leave a large margin beside. The
possibility of loss of human life should also be considered, though this
may seem a far cry from the question of repair costs.

Space Occupied--The space required for the boilers in a plant often
exceeds the requirements for the remainder of the plant equipment. Any
saving of space in a boiler room will be a large factor in reducing the
cost of real estate and of the building. Even when the boiler plant is
comparatively small, the saving in space frequently will amount to a
considerable percentage of the cost of the boilers. Table 2 shows the
difference in floor space occupied by fire-tube boilers and Babcock &
Wilcox boilers of the same capacity, the latter being taken as
representing the water-tube class. This saving in space will increase
with the size of the plant for the reason that large size boiler units
while common in water-tube practice are impracticable in fire-tube
practice.

TABLE 2

COMPARATIVE APPROXIMATE FLOOR
SPACE OCCUPIED BY BABCOCK & WILCOX
AND H. R. T. BOILERS

+------------+----------------+---------------+
|Size of unit|Babcock & Wilcox| H. R. T. |
|Horse Power |Feet and Inches |Feet and Inches|
+------------+----------------+---------------+
| 100 | 7 3 x 19 9 | 10 0 x 20 0 |
| 150 | 7 10 x 19 9 | 10 0 x 22 6 |
| 200 | 9 0 x 19 9 | 11 6 x 23 10 |
| 250 | 9 0 x 19 9 | 11 6 x 23 10 |
| 300 | 10 2 x 19 9 | 12 0 x 25 0 |
+------------+----------------+---------------+

BABCOCK & WILCOX BOILERS AS COMPARED WITH OTHER WATER-TUBE DESIGNS

It must be borne in mind that the simple fact that a boiler is of the
water-tube design does not as a necessity indicate that it is a good or
safe boiler.

Safety--Many of the water-tube boilers on the
market are as lacking as are fire-tube boilers in the positive
circulation which, as has been demonstrated by Mr. Babcock's lecture, is
so necessary in the requirements of the perfect steam boiler. In boilers
using water-leg construction, there is danger of defective circulation,
leaks are common, and unsuspected corrosion may be going on in portions
of the boiler that cannot be inspected. Stresses due to unequal
expansion of the metal cannot be well avoided but they may be minimized
by maintaining at the same temperature all pressure parts of the boiler.
The result is to be secured only by means of a