ROFF'S PATENT FOR WEIGHING VESSELS.

Grey River Argus, Volume XII, Issue 1143, 3 April 1872, Page 2

ROFF'S PATENT FOR WEIGHING VESSELS.

A discussion has been going on recently in the Melbourne papers regarding tho ballasting of ships, which has again brought Roffs patent for the weighing of the contents of vessels before the public. The following is the detailed description, as given by the Age, of the test to which this machine was recently subjected: — "Some eight or nine months ago we gave a notice of a new invention designed to accurately ascertain the weight of cargo taken on board or landed, and of water admitted into a ship by leak or otherwise. The Ecliptic, a barque of 500 tons, trading to Newcastle for coal, and now in this port, has tested the invention. Captain Elaridge states that it does its work so satisfactorily that it will in all probability come into speedy use for all classes of merchant vessels. Like most useful inventions, the principle of action and its application are extremely simple, consisting merely of a small tube passing into the water through the ship's bottom, and communicating with another and larger tube that rises to a height of three or four feet above the deck, near the mainmast. Having thus free communication with the water outside the ship, and being placed exactly in the vessel's centre of gravity, the water in the tube naturally Btands at the precise level of her line of flotation, whatever may bo her position, whether on an even keel, rolling, or pitching, with her stem or stern high out of wator. A small hollow copper ball floats on the surface of the water inside the tube, from which a cord, having a very small counter weight at its other extremity, passes over a drum that communicates motion to a train of wheelwork in connection with the pointer of an index dial, divided into hundredths. It will be easily understood that every, even the slightest, variation in the vessel's displacement will cause the water in the tube to rise or fall, and tho floating ball rising or falling accordingly, necessarily marks the change on the face of the indicator. So susceptible is it to these variations, that the Ecliptic having been loaded in the Hunter River with 482 tons 13cwt of coal, the difference of specific gravity on gettin < into Bait water was made distinctly perceptible on the dial plate, which rJso registered an increase of about a quarter of a ton in the ship's loading when three persons stepped on board on her arrival in Hobson's Bay. The index is so arranged as to make one complete revolution for every 600 tons, bat it can be set to any other rate that is desired. The expense of fitting it is inconsiderable, a complete machine for a large vessel not costing more that L 50."