`That is a minor matter,' Mein Herr carelessly replied. `But they have the comfort of knowing that, whether drowned or not, they are all lighter than water. We have not yet reached the standard of making people lighter than air: but we are aiming at it; and, in another thousand years or so--'

`What doos oo do wiz the peoples that's too heavy?' Bruno solemnly enquired.

`We have applied the same process,' Mein Herr continued, not noticing Bruno's question, `to many other purposes. We have gone on selecting walking-sticks -- always keeping those that walked best -- till we have obtained some, that can walk by themselves! We have gone on selecting cotton-wool, till we have got some lighter than air! You've no idea what a useful material it is! We call it "Imponderal".'

`What do you use it for?'

`Well, chiefly for packing articles, to go by Parcel-Post. It makes them weigh less than nothing, you know.'

`And how do the Post Office people know what you have to pay?'

`That's the beauty of the new system!' Mein Herr cried exultingly. `They pay us: we don't pay them! I've often got as much as five shillings for sending a parcel.'

`But doesn't your Government object?'

`Well, they do object a little. They say it comes so expensive, in the long run. But the thing's as clear as daylight, by their own rules. If I send a parcel, that weighs a pound more than nothing, I pay three- pence: so, of course, if it weighs a pound less than nothing, I ought to receive three-pence.'

`It is indeed a useful article!' I said.

`Yet even "Imponderal" has its disadvantages,' he resumed. `I bought some, a few days ago, and put it into my hat, to carry it home, and the hat simply floated away!'

`Had oo some of that funny stuff in oor hat to-day?' Bruno enquired. `Sylvie and me saw oo in the road, and oor hat were ever so high up! Weren't it, Sylvie?'

`No, that was quite another thing,' said Mein Herr. `There was a drop or two of rain falling: so I put my hat on the top of my stick -- as an umbrella, you know. As I came along the road,' he continued, turning to me, `I was overtaken by--'

`--a shower of rain?' said Bruno.

`Well, it looked more like the tail of a dog,' Mein Herr replied. `It was the most curious thing! Something rubbed affectionately against my knee. And I looked down. And I could see nothing! Only, about a yard off, there was a dog's tail, wagging, all by itself!'

`Oh, Sylvie!' Bruno murmured reproachfully. `Oo didn't finish making him visible!'

`I'm so sorry!' Sylvie said, looking very penitent. `I meant to rub it along his back, but we were in such a hurry. We'll go and finish him to-morrow. Poor thing! Perhaps he'll get no supper to-night!'

`Course he won't!' said Bruno. `Nobody never gives bones to a dog's tail!'

Mein Herr looked from one to the other in blank astonishment. `I do not understand you,' he said. `I had lost my way, and I was consulting a pocketmap, and somehow I had dropped one of my gloves, and this invisible Something, that had rubbed against my knee, actually brought it back to me!'