The generator is supported in the furnace by cast iron brackets represented by Figs. 12 and 13, built into the sides of the furnace for the projecting parts of the generator to rest on, where F, Fig. 11, is the fire place, A the ash-pit, and C part of the chimney. R represents part of the pipe that leads from the force pump to the generator, whence the water circulates round and round the spirals from the circumference to the centre of the under half of the generator, as cends the centre pillar P, then circulates outwards from the centre of the upper half of the generator to its circumference, and escapes by the pipe S, that leads to the cylinder of the engine. The pipe T is the one that conveys part of the escape steam from the cylinder into the chimney. This generator works a small high pressure engine, of which the following is a short description : The frame of it is of cast-iron, of the form of the upper part of Mr. Maudslay's portable engine with its parallel motion. The piston of the cylinder is six inches in diameter, and the length of the cylinder per mits the piston rod to make a stroke of seventeen inches. The steam is permitted to enter the cylinder alternately above and below the piston by means of a spring slide valve wrought by the engine, and has a stroke of one and two-eighths of an inch. The axis of the fly-wheel cranks, Ste. is two inches and a quarter square ; the rounded parts two and one-eighth inches in diameter. The fly is seven hundred weight. and six feet in diameter. In the steam-pipe that leads from the generator to the cylinder, there is a three way cock introduced, with a branch proceeding from it to the hot well of the engine, by which the steam may be permitted either to pass the cylinder, or by one-third turn of the cock into the hot well of the en gine. This three-way cock answers for stopping or starting the engine. As there is no space in this kind of generator, as in common engine-boilers, for the steam to condense or expand, the common throttle valve is not applicable to this kind of generator ; but in place of it, a spring slide valve is introduced in the steam-pipe between the three-way cock and generator, with a branch from it communicating with the branch pipe that leads between the three-way cock and hot well. This slide valve is raised and lowered against a very acute angled aperture by means of centrifugal balls, so as to permit a necessary regulating quantity of steam to escape into the hot well. In the pipe by which the steam escapes from the cylinder into the chimney, there is a branch to the hot well ; in this branch there is a cock by which the temperature of the water in the hot well is regulated. The forcing pump is wrought by the engine, and supplies the gene rator with water from the hot well. In a side vessel that communicates with the hot well, there is a forcing pump wrought by hand for starting the engine. Into this vessel additional water enters to supply the en gine, and where the height of the water in the hot well is regulated. As the engine is intended to work different kinds of machines y, either together or sepa rately, different powers are required.
To produce these several powers, there is a short branch from the steam-pipe near the generator, that reaches to a convenient place, where a steel yard safe ty valve is placed. On the lever of this safety valve, the safety valve weight is to be hung at divisions marked on it answering to the power required, and a corresponding length of stroke is also to be given to the forcing pump of the engine.
The engine was first publicly tried in January 1828, before it was connected with machinery of any kind ; but that it might meet with some resistance, a friction bar of iron with a considerable pressure was applied to the periphery of the fly-wheel, when the engine made eighty-eight double strokes per minute.
The engine was lately tried connected with grinding and turning-lathe machinery, and at the same time it wrought east-iron rollers bruising blear for lire clay.
Although the bleas were very irregularly fed into the rollers, yet the engine continued to make sixty-four double strokes per minute. A greater number might
have been obtained ; but from the irregular manner the bleas was fed in, there was reason to fear that the main axis of the engine might give way.
On the bottom and sides of vessels that have been long used for boiling fresh water, a calcareous crust is generally formed more or less in thickness.
It is proposed, if it shall be found that the spiral grooved generators are liable to be incrusted in this manner, that a water-tight cistern be placed somewhat higher than the generator. This cistern is to be con nected with the upper part of the generator by a pipe and stop-cock. There is also to he a branch pipe from the steam-pipe close to the under part of the generator, with a particular stop-cock, that when open, it shall cut off the communication between the generator and the slide valves. Let this cistern be filled brimful with water, and the cock at the bottom of the generator left open. If the cock of the cistern be opened, the whole water of the cistern will escape through the generator; and if the time it takes to escape be observed by a pen dulum or stop-second watch, the repetition of this ex periment at any time will show if the passage through the generator be contracted since last experiment. Should it be found to be so, it is then proposed to fill the generator with diluted muriatic acid, taking care to cut off the communication between it and the slide valves. After letting it remain in the generator a sufficient time, it is then to be washed out with warm water poured into the above-mentioned cistern. If the cistern be filled brimful it will serve to ascertain if the passage be clear, by observing the time it takes to pass through the generator. Repetitions of these ex periments will undoubtedly free the generator of all calcareous matter. But as none of the strong acids act on the crust formed by sea water, it is therefore proposed to proceed in the same manner with diluted sulphuric acid, taking care never to give time for much crust to form by sea water, so that by the diluted sulphuric acid partly acting on the iron, it shall effect the removing of an imperfect crust pro duced from salt water ; the generator to be always thoroughly washed out with warm water.
The length of time that this engine has been in constructing, gave ample time to devise improve ments. Several were proposed, but few of them were thought of in time to be introduced without making material alterations on the parts made ; such as im provements in the manner of constructing generators of greater strength, but of which it is unnecessary to lengthen this paper with a description. However, one thing may be mentioned, as it would add to the improvement of the engine. In place of working the escape steam slide valve by the immediate action of the centrifugal balls, it was proposed that the axis of a bevelled wheel should be turned by the machinery of the engine, and which is to turn other two bevelled wheels on one axis. These two last mentioned wheels are neither of them to be fixed to the axis, but both to slip round freely upon it, turning in contrary di rections as they receive motion from the opposite sides of the first mentioned wheel. A locking stub box is fitted upon the axis between the two wheels, and can, by moving it one way or the other, be made to lock either of the wheels to the axis at the same time that it leaves the other disengaged. It is proposed that the centrifugal balls shall shift this stub box back or forward as their centrifugal motion shall be affected by the velocity that they receive from the engine. The axis of these two wheels is proposed to be so connected with the escape steam slide valve, that, on its turning one way round it shall raise the valve to let the steam escape, and by turning the contrary way, it shall de press the valve that less may escape ; and it is further proposed, that there shall be spring sockets on the axis of the first wheel, to prevent any part giving way when the valve is fully wrought up or down. In like manner it is proposed to work the furnace damper for regulating the heat of the fire.