Orchard's Vacuum Engine
In 1826 there was published in "Mechanics' Magazine," London, a communication from a Mr. Orchard, concerning an invention he considered himself as having made. The account is published in his own words, and is as follows:
A is an iron reservoir nearly filled with mercury; B, a tube twenty-four inches long, having its lower end inserted in that reservoir; and C and D, two cocks for the convenience of filling the tube B. From this another tube M proceeds at right angles, to the vessel G. In this latter tube is the cock F, to admit of, or shut off, a communication between the tube and the vessel G. This communication being closed, the tube B is carefully filled with mercury; after which the cock D is closed and the cap E screwed on.
The vessel G is to be filled with mercury through the cock H, the pipe I being open to allow of the escape of air. When this vessel has been filled, the cock H should be closed and its cap screwed on; and the pipe I be also closed by a valve, which is to be pressed tight by the cap on the head of the pipe. I is a vent-pipe, open at the top. The space represented by the double lines is a panel of thick plate glass having two horizontal lines described on its surface, whereby the attendant may observe the quantity of mercury within the vessel.
The cock F being closed, a quantity of mercury must be allowed to run out of the vessel G, equal to the space 1, 2, 3, 4, which space will become a vacuum. If, therefore, the cock L be then opened, to allow of the discharge of a certain quantity of mercury on the wheel, and the cocks C and L also opened, the mercury will continually rise from the reservoir A into the vessel G, and thence be discharged on the wheel, whence it will again fall into the vessel A, to keep up the supply. The cock F must be so adjusted as to admit into the vessel G a quantity of mercury equal to that which is discharged by the cock L. This can be ascertained and regulated by means of the panel of glass above described.
The specific gravity of mercury being 7½ ounces, it is evident that but a small quantity of it is required to turn the wheel, which has no friction but that of the axis on which it turns.
