These experiments took place about the year 1826; since which time the engine of Mr. Gurney has undergone very considerable improvements; and this machine may now be considered to have attained a state of perfection which fits it for immediate use for light loads, as a means of transport for passengers and goods, for short stages, but never can pay its expense for construction and conducting it like all the others, but on railroads it can be used to advantage.
The grate-bars of the furnace in this engine, are a series of parallel tubes stretching from the front to the back, and sloping slightly upwards. In the front these tubes are fastened in the side of a strong metal cylinder, which extends across the front under the door of the fire-place. The extremities of the same tubes at the back of the grate are connected with the ends of a corresponding series of upright tubes, which, in fact, form the back of the furnace. The upper extremities of these last tubes are connected with the extremities of a third series, which form the roof of the furnace, sloping slightly upwards from the back towards the front. In the front, their extremities are fastened in the side of a strong metal cylinder, which extends across the front of the fireplace over the fire-door, and corresponds with the other cylinder already described. These two cylinders are connected by two large upright metal tubes, one placed at each side of the fire-door, and forming the sides of the front of the furnace. From this description, it will be easily perceived, that the tubes and cylinders which surround the furnace, afford the means of a complete circulation round it, communicating freely with each other at their several points of connection. The cylinder, which is placed above
