From Leonard Darwin to Horace Darwin [18 November 1872]

Dear Jim

Yours undated to hand.

Rummmy you should take an interest in our football—just like Roger. Well we have drawn a bie for the second round so we dont play till the third round not for some time.

To business.

You remarked in your favour of the —^th. that you did not think elect. magnets could do the work. That set this gigantic intellect on the qui vive.

I have never tried to draw what I am going to draw not so I may fail. [DIAG HERE]

I suppose you consider the difficulty is to get enough motion. Well the coil is separate from the soft iron inside just touching it. In front of the magnet there are discs of soft iron fastened together so that they can move into the magnet but can only move a certain distance wasy. Now turn on the electricity. The first disc will be drawn into the magnet and by the system of levers the coil will at the same time be drawn over the disc. So we get the magnet as good as new to work on the second disc.