210 ANNUAL OF SCIENTIFIC DISCOVERY. 



totally free from these objections. Our readers may make an excel- 

 lent model of the new pump by fitting water-tight into one end of a 

 cylindrical glass gas chimney a piece of wood or cork, in the centre 

 of which is an aperture, closed within the glass cylinder by a flap of 

 leather, which will act as a simple, but tolerably water-tight valve ; 

 and selecting for the plunger a thick rod of wood that nearly fills the 

 cylinder. To work the apparatus it is only necessary to insert the 

 plunger in the cylinder, fill the space around it with water, and place 

 the closed end of the cylinder in a small quantity of that fluid. 

 "When the plunger is drawn up, the valve opens, and water rushes 

 in to supply the vacuum. When the plunger is then pushed in 

 again, the water flows out through the upper end of the cylinder; and 

 thus the process may be continued for any length of time. It is 

 evident that the fluid may be made to issue from a spout or tube, if the 

 upper end of the barrel is enlarged. The principle on which this 

 pump produces its effect is the same as that of the common pump, 

 but it might be supposed that, instead of water rushing up through 

 the valve, water, and even air, would pass down from around the 

 plunger. This, however, is not the case ; and it is the most curious 

 circumstance connected with the apparatus. It may be accounted for, 

 however, by the capillary attraction which exists between the plunger 

 and barrel. Experiment alone can show how large such a pump 

 may be made, or from what depth it would cause water to ascend ; 

 but there are most probably many purposes for which it would answer 

 well. 



CURIOUS PHYSICAL EXPERIMENT. 



An interesting experiment, which, though not new, is not generally 

 known, may be performed as follows : Roll up a large card into a tube 

 a quarter of an inch in diameter, and make the joint tight by a little 

 sealing-wax. Then cut a disc of card two inches in diameter, make a 

 hole through its centre exactly big enough to admit the tube. Seal- 

 ing-wax the card disc on to the top of the tube so as to form a flange, 

 taking care not to let the tube project above the surface of the disc. 

 Cut another card disc of the same diameter, and lay it on the former, 

 holding the tube quite upright with the disc uppermost. Blow gen- 

 tly through the tube, and the loose disc will be thrown off the flange. 

 Iteplaee it, and blow with great vehemence. The disc will then not 

 be thrown off, but will remain close to the flange, vibrating strongly. 

 The loose disc may then be placed on the table, and the tube with the 

 flange downwards held very near it. On blowing violently the loose 

 disc will spring up toward the flange and vibrate as before. 



TESTING OF CHAIN CABLES. 



An interesting paper on the above subject was recently read by Mr. 

 Paget, C. E. before the Society of Arts. The average tenacity of the 

 bars of which the links are made is stated to be 24 tons per square 

 inch ; of this 28.75 per cent is lost in the finished link, in conse- 

 quence of (1) the geometrical form of the link, (:.^) the crushing stress 

 undergone by the inside of the crowns, (3) the deterioration of the 

 iron in bending, and (4)the loss of strength at the welds. As to the 

 proper tests of the ruMe, Mr. Paget suggests the breaking of a por- 

 tion by hydraulic pressure as affording the surest guide to the quality 



