TO SHOW THAT AIR HAS WEIGHT

Drive a thin nail by the exact centre of a long rod such as a metre stick or a yard stick. Balance the stick by resting the nail on the rims of two drinking glasses. Make a rider out of a short length of wire and place it on the end of the stick which requires weight to balance. Move the rider unless the stick balances perfectly.  Hang a rubber balloon and a rubber band on single end of the stick.   Now   counterbalance   the balloon exactly with a few weights on the other end of the stick. Mark the place on the stick where the balloon and counter-weight were placed. Take away the balloon and inflate it, using a bicycle pump. Close with the rubber band. Next hang the balloon and counterweight precisely where they were before