184 ANNUAL OF SCIENTIFIC DISCOVERY. 



DETERMINATIONS OF FREE OXYGEN. 



At a meeting of the Manchester Literary and Philosopliical 

 Society, Mr. Peter Hart described his method of making rapid 

 determinations of free oxygen. The apparatus required consists, 

 in addition to an ordinary pneumatic trougli, of two tulies, each 

 one-half inch in diameter and IG inch»;s long, closed at one end. 

 One of the tubes is graduated into fiftieths of a cubic inch, and 

 the other is coated internally with phosphorus. This is ellected 

 by dropping into the tube a few pieces of phosphorus; it is then 

 to be closed by a sound cork, and the piiospliorus (melted by 

 immersing the tube in hot water) may be spread in a thin coating 

 over the interior by turning it round as it cools. On cooling, the 

 cork is to be withdrawn, the tube filled with water, and a piece 

 of India-rubber tube tied securely over the mouth. This com- 

 pletes the apparatus. Tiie modus operandi is as follows : Both 

 tubes are filled with water, and allowed to remain in the trough, 

 a portion of the air to be examined is passed into the measuring 

 tube, which is now allowed to remain for 5 minutes in the trough 

 to allow it to attain the same temperature as the water. It is 

 lifted until the water is at the same level within and without, and 

 may then be closed by the finger, and withdrawn from the trough. 

 The volume is easily noted. This done, it is connected by the 

 India-rubber joint with the phosphorus tube, into which the air 

 is allowed to flow. The whole may now be placed for half an 

 hour in the trough, when tiie gas may be poured back into the 

 measuring tube, the level once more taken, and the volume read 

 oil' i!i the same way as before. The loss is oxygen. No claim is 

 made for strict scientific accuracy in connection with this appara- 

 tus ; its so)e merit consists in its oftering an easy and rapid means 

 of approximately determining the free oxygon in an atmosphere. 

 i\\ the working of sulphuric acid chambers it has been found 

 extremely valuable, and possil)ly may be found so for other tech- 

 nical inquiries. — Mechanics'' Magazine. 



DEFLECTION OF BEAMS. 



Professor W. A. Norton, of Yale College, at the meeting of the 

 American Association, at Salem, communicated the principal results 

 of a series of experiments which he iiad madt^ to test the theoret- 

 ical laws of the deflection of beams exposed to a transvei-se 

 strain. In the experiments the beam rested on the supports at 

 the ends, and was loaded in the midille. The accepted formula 

 gives the following laws: (1) The di'fiection is proportional to 

 the pressure ; (i) inversely to the breadth ; (:>) and to the cube 

 of the depth ; (4) directly proportional to the cube of the length. 

 The results of the expcrim'-nts (fully ('X})lained by diagrams and 

 tables) show that the dcllcction is approximately proportional to 

 the pressure, but, strictly speaking, increases according to a less 

 mind law, the neutral axis of the cross section of the stick shift- 



