It can detect a gun as easily if it is in a wood or in a building as if it were on a hill-top.
"Simple as it appears, however, it is not so easy as one might think to make a practical ally of sound ranging.

We have succeeded.

The Germans failed.

Towards the end of the war at least ninety per cent, of the German artillery was marked down accurately by these means; and the staff employed on sound-ranging and flash-spotting (the last a kindred method depending on a mixture of observation and mathematics) had grown from _four_ in 1914 _to four thousand five hundred_ in 1918.
"Casualties have been heavy, and the work arduous.

But those responsible for it have, at any rate, 'done their bit.'" This is just one instance, such as we ignorant at home can more or less follow, of that concentration of British wit and British perseverance on the terrible business of war which carried us to our goal.