I looked out of the window. The ambulance had gone back, but the driver of the car had evidently waited to call up his office for instructions. I beckoned to him, and together Kennedy and I placed the packages in the car.
Thus we were able quickly to get back again to the wharf where the Haytien was berthed. Instead of going aboard again, however, Kennedy stopped just outside, where he was not observed and got out of the car, dismissing it.
In the office of the steamship company, he sought one of the employés and handed him a card, explaining that we were aiding Burke in the case. The result of the parley was that Kennedy succeeded in getting to the roof of the covered pier on the opposite side from that where the ship lay.
There he set to work on a strange apparatus, wires from which ran up to a flag pole on which he was constructing what looked like a hastily improvised wireless aerial. That part arranged, Kennedy followed his wires down again and took them in by a window to a sort of lumber-room back of the office. Outside everyone was too busy to watch what we were doing there and Craig could work uninterrupted.
"What are you doing?" I asked. "Installing a wireless plant?"
"Not quite," he smiled quietly. "This is a home-made wireless photo-recording set. Of course, wireless aerials of amateurs don't hum any more since war has caused the strict censorship of all wireless. But there is no reason why one can't receive messages, even if they can't be sent by everybody.
"This is a fairly easy and inexpensive means by which automatic records can be taken. It involves no delicate instruments and the principal part of it can be made in a few hours from materials that I have in my laboratory. The basis is the capillary electrometer."
"Sounds very simple," I volunteered, trying not to be sarcastic.
"Well, here it is," he indicated, touching what looked like an ordinary soft glass tube of perhaps a quarter of an inch diameter, bent U-shaped, with one limb shorter than the other.
"It is filled nearly to the top of the shorter limb with chemically pure mercury," he went on. "On the top of it, I have poured a little twenty per cent sulphuric acid. Dipping into the acid is a small piece of capillary tube drawn out to a very fine point at the lower end."