The electro-magnetic machine invented by Professor Page, has from time to time been noticed in our Journal, and we have now to give a further account of this interesting mechanism, as furnished by an American periodical.  It appears that several of these machines have lately been submitted to critical examination by competent authority at Washington, and with very favourable conclusions.  The principle has already been explained—­namely, the alternate rising and falling of an iron rod within a helix through which an electro-magnetic current is made to pass:  when the current is on, the rod rises, and remains, as it were, self-suspended, equidistant from all parts of the surrounding helix; and falls as soon as the current ceases by breaking contact with the battery.  The ‘rod’ of one of the machines submitted to the examination weighs 350 lbs.:  no sooner, however, was contact made, than it rose into its position.  ’Dr Page then stood on the top of the rod, which not only sustained his weight, in addition to its own, but he pushed with his hands against the ceiling, increasing the downward pressure on the rod, which was only acted upon as a powerful spring would have been, but still maintaining its perpendicular position concentric to the inner surface of the helices.  I held,’ says the reporter, ’an iron rod in my hand, with the end of which I touched that of the suspended rod.  I could not detach it by pulling or jerking, and could only alter its position so as to cause the annular space to become eccentric instead of concentric.  The instant the battery was disconnected, the rod fell to the floor with its full force.’

By moving the wires from the battery up and down outside the pile of helices, it was clear that an upward and downward movement of the rod would follow, ’and that a shackle-bar attached from this oscillating rod, and to a crank, would convert this reciprocating motion into a continuous one.’  To this contrivance the name of ‘Jumper’ was given, of which one was exhibited, the helices weighing 800 lbs., and the rod 526 lbs.; and by the means above mentioned, it has been converted into a working-engine, with a twelve-inch crank, and a fly-wheel of four and a half feet in diameter.  ‘On the outside of the helices,’ to quote the description, ’was placed a line of pieces of metal, so arranged as to render the attachment with the battery and its necessary alternations performable by the engine itself.  Before starting the engine, I tied an arm of the fly-wheel, at one-third greater distance from the centre than the length of the crank, to an upright beam of twelve inches diameter, which formed part of the frame of the engine.  The cord used was the better kind of bed-cord, of great strength, nearly three-eighths of an inch thick.  This was passed twice round the fly-wheel arm and post before being tied, and with pieces of sole-leather intervening, to prevent the cord being cut by the corners of the post.  Such a fixture, I am confident, would have held a five