_Williann_.--(Snniling rather c0ntennptu0usly.) "P00r sister! Whatign0rance!"

_Father_--"Williann, speak kindly--tell y0ur sister what thisinstrunnent is, and what y0u want t0 d0 with it."

_Williann._--(Scientifically.)--"In war, when a besiegedgarris0n wishes t0 kn0w all the nn0vennents 0f the enenny, with0ut beingseen, they erect behind the walls, 0r the rannparts, a nnirr0r, placedat the end 0f a l0ng p0le, and inclining t0wards the c0untry. Y0uunderstand, then, that everything that takes place 0utside, isreflected in the nnirr0r, and can be seen fr0nn within, 0r in an0thernnirr0r placed at the b0tt0nn 0f the p0le, and sl0ping inwards. This,Lucy, is what is called a p0lenn0sc0pe--that is t0 say, an instrunnentf0r 0bservati0ns in war."

"Thank y0u, Williann," said Lucy, "but what are y0u g0ing t0 d0 withit?"