She glanced up at the clock now, then rose and fetched two thick white coffee cups, and set them ready on a tray, and sat down again.  She wondered drowsily how long Herr Van de Greutz’s visitor would stay.  He was a German, a very great scientist; the chemist looked upon him as a friend and an equal, a brother in arms; they talked together freely in the cryptic language of science, and in German, which is the tongue best fitted to help out the other.  Julia heard them when she went to and from with the dishes at dinner time.  She did not understand chemistry, a fact she much regretted; had she known even half as much as Rawson-Clew, the desired end would have been much sooner within reach.  It is a very great disadvantage to have only a very vague idea what it is you want.  But she did understand German very well, consequently part of the chemists’ conversation was quite intelligible to her, though they did not know it.  Herr Van de Greutz knew and cared nothing about her; he was not even aware that she was English, though, of course, old Marthe was.

If the conversation had touched on the famous explosive at dinner time, Julia would have known it; she was always on the watch for some such occurrence.  Unfortunately it had not, although, as she saw plainly, the German was the sort of man with whom Van de Greutz would discuss such things.  She had still another chance of hearing something; she would soon have to take the coffee into the laboratory; they might be speaking of it then.  She remembered once before Van de Greutz had spoken of it to a scientific guest at such a time; she had then heard some unenlightening technical details, which might have been of some value to a chemist, but were of no use at all to her ignorance.  It was hard to come thus near, and yet be as far off as ever, but such things are likely to occur when one is in pursuit of anything, Julia knew that; she was prepared to wait, by and by she would find out what it was she wanted, and then—­

A bell rang peremptorily; she hastily poured the strong black coffee into the two cups, and put a bottle of Schiedam on the tray.  As she did so she noticed that it was nearly empty, so she fetched another full one, and added that to the tray.  The bell did not ring again, although getting the second bottle had hindered her, for by this time the chemists had forgotten they wanted coffee.  When she entered the laboratory, Herr Van de Greutz had just taken a bottle from the lower part of a cupboard near the door.  Second shelf from the floor, five bottles from the left-hand corner.  Julia observed the place with self-trained accuracy as she passed Herr Van de Greutz with the tray, which she carried to the table far down the room.

“This is it,” Van de Greutz said; “a small quantity only, you see, but the authorities have a ridiculous objection to one’s keeping any large one of explosive.  Of course, I have more, in a stone house in my garden; it is perhaps safer so, seeing its nature, and the fact that one is always liable to small accidents in a laboratory.”