In this last example the tender is atttached to the engine in the manner usual upon other railways; but in fig. 80 the tender is stuck on to the end of the engine and is supported upon wheels which are put into revolution by means of rods proceeding from the nearest wheels of the engine, which wheels are themselves put into revolution by means of gearing. Upon the third axle of the engine a toothed wheel is

EIGHT-COUPLED WHEEL ENGINE OF SEMMERING INCLINE, 1861.

fixed, which gears into another toothed wheel of the same size, and this last wheel gears into another toothed wheel on the next axle and turns it round. The positions of these toothed wheels are shown in the figure by dotted circles.

In some of the forms of engine with four cylinders, and six coupled axles, three of the axles and two of

the cylinders are attached to a framing, on which the boiler rests on two points, one on each side of the fire-box, while the other three axles and the other two cylinders are attached to a bogie or independent carriage travelling upon a centre on which the smoke box rests, and this bogie accommodates itself to the curves of the road. Such a device, however, is only a clumsy approximation to two independent engines, and the use of two engines with the footplates brought together as recommended by me in my "Treatise on the Steam Engine' in 1845, so that one set of handles might govern the movements of both engines and one stoker fire both furnaces, would

be greatly preferable to the use of those uncouth leviathans. The great height of these engines relatively with the width of base necessarily makes them top heavy; while the relative narrowness of the gauge -which limits the diameter of the barrel of the boiler and consequently the area for the introduction of the tubes has led to such crowding and such contraction of the areas in this part, as to diminish the efficiency of the heating surface, besides leading to other inconveniences.

The principal dimensions of some of the more remarkable of the continental locomotives are given in the following table :

To this has to be added heating surface of superheater 239 square feet.

AMERICAN LOCOMOTIVES.

The American locomotives differ in several of their features from those which are employed in this country, and there is nearly always some special feature in the traffic, the fuel, or the climate to warrant the distinction, and to render it judicious; but the difference is not nearly so great as that which obtains in some of the continental locomotives. The fore part of the engine is usually supported upon a small four-wheeled truck or bogie; a large cone is frequently placed around the chimney for catching the sparks, which are very inconvenient when wood is burned; but many American locomotives now burn coal. When a spark-catcher is used, a sort of inverted saucer over the mouth of the chimney deflects the sparks downwards into the cone, whence they are drawn off at intervals by a small door. The top of the cone is covered with wire gauze. In the front of the engine is an arrangement of bars of iron called a cowcatcher, for throwing any object off the line which may happen to be upon it; and this apparatus also acts like a snow plough, should snow have fallen on the line. Fig. 82 is a vertical section of a first-class American locomotive, exhibited in Paris in 1867, by the great locomotive works of Patterson, fifteen miles from New York. The engine is an outside cylinder engine, with four coupled wheels and a bogie under the fore part. The following are some of the chief dimensions: Diameter of cylin