safely
to-morrow. If necessary, I'll get an order for them."

The station-agent reluctantly yielded; especially as a small green
banknote figured in the transaction. Craig and I tenderly lifted the big
bottles in their cases into our trap and drove back to our rooms in the
hotel. It quite excited the hangers-on to see us drive up with a lot of
empty five-gallon bottles and carry them up-stairs, but I had long ago
given up having any fear of public opinion in carrying out anything
Craig wanted.

In our room we worked far into the night. Craig carefully swabbed out
the bottom and sides of each bottle by inserting a little piece of
cotton on the end of a long wire. Then he squeezed the water out of the
cotton swab on small glass slides coated with agar-agar, or Japanese
seaweed, a medium in which germ-cultures multiply rapidly. He put the
slides away in a little oven with an alcohol-lamp which he had brought
along, leaving them to remain overnight at blood heat.

I had noticed all this time that he was very particular not to touch any
of the bottles on the outside. As for me, I wouldn't have touched them
for the world. In fact, I was getting so I hesitated to touch anything.
I was almost afraid to breathe, though I knew there was no harm in that.
However, it was not danger of infection in touching the bottles that
made Craig so careful. He had noted, in the dim light of the station
lamps, what seemed to be finger-marks on the bottles, and they had
interested him, in fact, had decided him on a further investigation of
the bottles.

"I am now going to bring out these very faint finger-prints on the
bottles," remarked Craig, proceeding with his examination in the better
light of our room. "Here is some powder known to chemists as 'grey
powder'--mercury and chalk. I sprinkle it over the faint markings, so,
and then I brush it off with a camel's-hair brush lightly. That brings
out the imprint much more clearly, as you can see. For instance, if
you place your dry thumb on a piece of white paper you leave no visible
impression. If grey powder is sprinkled over the spot and then brushed
off a distinct impression is seen. If the impression of the fingers is
left on something soft, like wax, it is often best to use printers' ink
to bring out the ridges and patterns of the finger-marks. And so on
for various materials. Quite a science has been built up around
finger-prints.

"I wish I had that enlarging camera which I have in