Let everybody try to do everything they fancy.

Even if they fail, they will have learnt at least that they cannot do it.
But now--and this is a secret which you would never find out for yourself, at least without the help of a microscope--the greater part of this lump of chalk is made up of things which neither Analysis can perfectly take to pieces, nor Synthesis put together again.

It is made of dead organisms, that is, things which have been made by living creatures.

If you washed and brushed that chalk into powder, you would find it full of little things like the Dentalina in this drawing, and many other curious forms.

I will show you some under the microscope one day.
They are the shells of animals called Foraminifera, because the shells of some of them are full of holes, through which they put out tiny arms.