P1 and P2 are two pans suspended from the lower end of the spring. Above pan P3 is an index head B. The lower
	pan P2 and attachments are immersed in water in th& cylinder G. Reading a is taken on the graduated scale after properly adjusting the apparatus, so that the index head lies against the upper part of the scale. The stone is then placed in the upper pan, the amount of immersion is adjusted to the same level as before by lowering the level of water. Reading b is now taken. The stone is now placed in P2 inside water, and the level of water again adjusted as before, and reading c is now taken.