My dear Father,

Your problem I understand to be this¹

Drop a marble down AB on to the inclined plane BC,—find the inclination of BC to the horizon so that the range BC may be a maximum. If the marble is perfectly elastic the inclin. is 30^o to horizon or 60^o to the vertical; if of glass (on to a glass plane) it is 29^o; if of tight packed wool or of iron it is 21^o. And the less elastic the ball & plane are the less must be the inclin. to the horizon²

I have no conception what the elasticity of water on a leaf would be; I fancy it is rather the upper part of the drop wh. splashes off the lower part & then what we require is the elasticity of water on water. From the height wh. water splashes I sh^d. think the elasticity must be pretty great. I am thinking however of trying an experiment wh. may give a clue—by squirting ink out of a very fine syringe onto inclined sheets of paper & observing the pattern. I have got a syringe but it is too coarse.

Judging from the marble I sh^d. guess the leaf sh^d. be³