Science and Invention.

Alexandra Herald and Central Otago Gazette, Issue 452, 15 December 1904, Page 7

Science and Invention.

STEEL caskets for the bodies of those who die suddenly on shipboard are being carried on many of the transatlantic liners. The remains are placed in them and hermetically sealed.. The whirh'ng winds of Arabia sometimes excavate sand pits to the depth of 200 ft., the rim .usually being three times that length in diameter. A sand pit thus made may be entirely obliterated in a few hours, and another excavated within a short distance of it;. A NEW ROTARY ENGINE. A new rotary steam-engine, said to be adapted for automobile purposes, is being exploited. Like most rotary engines, it is of! simple and compact design, and is claimed to be fool-proof. It comprises four roller valves which roll on the intarior surface, of-the cylinder when the engine is in motion, and the frictional loss due to the motion of the slide-valve in an ordinary reciprocating engine is therefore avoided in this engine; | The trial consisted of nine separate runs of one-half hour each, readings being taken every five minutes during r each run. exhaust steam was condensed suriace the condensing water caught and weighed after each run v A separator was used to dry the steam; 'with a throttling calorimeter to detect thff moisture present. Readings of the thermometer on this were taken every minute throughout the runs. The developed horse-power was measured by a Prony brake, length at arm sft. 3in., arm resting on platform scales. First run was made with no load to determine friction, and thereafter a load increasing by lib each run put on, Duration of run 7J hours, hbifer

pressure gauge average 98:13, average r.p.m. 1,242, total condensed water 1,4581b, developed horse-power 9.79, length of brake arm s,|ft., mechanical efficiency 91 percent; THE T)<IJRD LAW OF MOTION Have you ever thought why it is that when the propeller of a steamer revolves, in the water, the vessel moves. If the propeller, or screw, turns to the right, like of a dock, the ship is usually forced ahead. We can see the water churned into foam and driven away from the stern, but that does not account for th 6 motion of the ship. If the water offered no mere frictional resistance than it does, but was less easily tossed about by the propeller blades, the ship would move the faster. If the liquid in which the ship floats was as thick as butter and yet produced no more friction than water does, there would be practically no slip to the screw, and the ship would go ahead at each revolution, a distance about equal to tbe pitch of the screw. The. resistance of the water to the propeller action is what makes the ship move forwatd. The water objects, so to speak, to being driven back and away from the stern, and it exerts a pressure upon the revolving screw, and this pressure tends to drive the propeller itself forward, and cause it to crash into the stern plates of the ship. At the front end of the shaft, near the engines, is placed the thrust bearing or pillow-block. On the portion of the shaft within this bearing .there are several square-faced collars, and theso fit into depressions in the bearing. When the pressure of the water tends to make the propeller beat its way through the stern, and-shove the .shaft towards the bow, the collars Jof ,the thrust-block resist this dangerous motion, and, keeping shaft and propeller where they belong, transfer the motion to the wholo ship. The movement of the ship is then the result of the mutual action of two bodies on each other .which are always equal and exerted in contrary directions. That is one way of stating Newton's third law of motion. If anybody presses or draws another, it is justas much pressed on or drawn itself by tra second body. Almost anyone, if asked how much does a table press up on a 21b hamr nier laid on its surface, would, without thinking, probably reply, ' Nothing at all,' forgetting that the table presses up as much as the hammer presses down. The third law of motion amounts briefly to this; ' Action and re-action are always equal and opposite.' A curious example of how evolution takes care that the action of the * third, law' shall not harm certain birds of strong and rapid, though sometimes irregular, flight was given by Mr C. J. Maynard at a recent meeting of the Boston Scientific Society. The wishbone, as we call it, or the furcula, as they speak of it in Boston, is really, in a bird, the union of the two bones which correspond to the collar-bone in man. The wishbone receives the pressure caused by tho wing strokes of the bird in flight. Birds like the eagle, whose wing strokes are powerful, and where the bird is in the habit of turning suddenly to the right or left, put a heavy strain on the wishbono. The ctrain is greatest when the bird is making a sharp turn, for then the wing pressure is all on one side. The eagle's wishbone has become a solid round arch capable of sustaining considerable end thrust without buckling or springing, or allowing the wing to drive in on the breast, as would be the case with a slender, sharp-pointed bone, such as the spring chicken has, and which we are all familiar with. We have often seen two people break this sharp-pointed bone after dinner to see which shall have the most of the meriy thought. The eagle's arched wishbone would not yield in that way to an easy pull. It is interesting to trace the action of Newton's third law of motion to the movement of the locomotive along the track. The third lavy is involved in why an engine moves, but the solution of the problem has already been given,