[2] 1 ounce avoirdupois weighs 28A.349 grammes. [3] 1 mA"tre equals 39A.37 English inches. _Rectangular plates about 21 inches_ (0A.525 m.) _by 10 inches_ (0A.248 m.) _and 1/6 inch_ (0A.004 m.) _thick_. The frame with the glass inserted was laid on the ground, and in the middle of the plate a weight of more than 10 lbs. (5 kilogrammes[4]) was placed, and upon it as a base, other weights were placed, care being taken to avoid all shock. [4] 1 kilogramme = 2A.2 lbs. avoirdupois. 1Aš _Ordinary glass_, broke with a weight of about 70 lb. (35 kilos.) having resisted weights of from 30 to 50 lb. 2Aš _Toughened glass_ resisted fracture until a weight of more than 510 lb. (255 kilos.) had been added, and then was not broken. The experiment was not carried to its limit for want of weights. _Rectangular plates, about 13 inches_ (0A.325 m.) _by 10 inches_ (0A.248 m.) _and 1/5 inch_ (0A.005 m.) _thick_. These plates were allowed to fall flat on to a floor of wood or thrown to a distance and allowed to fall. 1Aš _Ordinary glass_ allowed to fall flat from a height of 1-2/10 inch (0A.03 m.) was broken at the first trial. 2Aš _Toughened glass._ Thrown to a height 6 feet 6 inches (2 mA"tres) and to a distance of 13 feet (4 mA"tres) was also broken at the first trial. The piece, however, which had sustained the weight of 510 lb. did not break till the fourth trial. _Rectangular plates, about 10 inches_ (0A.245 m.) _by 6 inches_ (0A.157 m.) _and 1/4 inch_ (0A.007 m.) _thick_. These plates were subjected to the same kind of tests as the foregoing. After raising them to a given height they were allowed to fall flat upon a wooden floor. 1Aš _Ordinary glass_ raised to a height of 20 inches (0A.50 m.) was broken on falling. 2Aš _Toughened glass_ resisted successive falls of from 20 inches (0A.50 m.), 32 inches (0A.80 m.), 5 feet (1A.50 m.), and 5 feet 7 inches (1A.70 m.), but was broken when dropped from a height of 6 feet 6 inches (2A.0 m.). _Rectangular plates about 10 inches_ (0A.245 m.) _by 6 inches_ (0A.157 m.) _and 1/5 inch_ (0A.006 m.) _thick_. Placed in the frames, they were held in position in the rabbets by laths nailed to the sides so as to prevent any play. The frames were raised to different heights and allowed to fall in such a manner as to cause as much vibration as possible. 1Aš _Ordinary glass_ was broken with a fall of about 2 feet (0A.60 m.). 2Aš _Toughened glass_ resisted falls from heights of 3 feet 3 inches (1 mA"tre), 6 feet 6 inches (2 mA"tres), 8 feet (2A.50 m.), 9 feet 9 inches (3 mA"tres), and 14 feet 6 inches (4A.50 m.). It was only broken by a fall of 19 feet 6 inches (6 mA"tres). _Rectangular plates 6 inches_ (0A.158 m.) _by 4-3/4 inches_ (0A.120 m.) _and 1/5 inch_ (0A.006 m.) _thick_.