the equilibrium of
the glass inside it.

Ringing the bell of one of the houses in Endsleigh Gardens, Mr. Tertius
was presently confronted by a trim parlourmaid, whose smile was ample
proof that the caller was well-known to her.

"Is the Professor in, Mary?" asked Mr. Tertius. "And if he is, is he
engaged?"

The trim parlourmaid replied that the Professor was in, and that she
hadn't heard that he was particularly engaged, and she immediately
preceded the visitor up a flight or two of stairs to a door, which in
addition to being thickly covered with green felt, was set in flanges of
rubber--these precautions being taken, of course, to ensure silence in
the apartment within. An electric bell was set in the door; a moment or
two elapsed before any response was made to the parlourmaid's ring. Then
the door automatically opened, the parlourmaid smiled at Mr. Tertius and
retired; Mr. Tertius walked in; the door closed softly behind him.

The room in which the visitor found himself was a large and lofty one,
lighted from the roof, from which it was also ventilated by a patent
arrangement of electric fans. Everything that met the view betokened
science, order, and method. The walls, destitute of picture or ornament,
were of a smooth neutral tinted plaster; where they met the floor the
corners were all carefully rounded off so that no dust could gather in
cracks and crevices; the floor, too, was of smooth cement; there was no
spot in which a speck of dust could settle in improper peace. A series
of benches ran round the room, and gave harbourings to a collection of
scientific instruments of strange appearance and shape; two large
tables, one at either end of the room, were similarly equipped. And at a
desk placed between them, and just then occupied in writing in a
note-book, sat a large man, whose big muscular body was enveloped in a
brown holland blouse or overall, fashioned something like a smock-frock
of the old-fashioned rural labourer. He lifted a colossal, mop-like head
and a huge hand as Mr. Tertius stepped across the threshold, and his
spectacled eyes twinkled as their glance fell on the bag which the
visitor carried so gingerly.

"Hullo, Tertius!" exclaimed the big man, in a deep, rich voice. "What
have you got there? Specimens?"

Mr. Tertius looked round for a quite empty space on the adjacent bench,
and at last seeing one, set his bag down upon it, and sighed with
relief.

"My dear Cox-Raythwaite!" he said, m