on nitrogen, and give out oxygen. They further learned that certain
germs make nitrogen, just the same as we found that certain germs made
carbonic gas in the dough; so that the United States Department of
Agriculture, through its chemical division, concluded to set the germs
to work, and the department will now send a box containing millions of
the tiny creatures to any farmer who applies for them."

"When they get them, how do they set them to work?"

"The germs are thrown into a tub of water, and the seed, like corn, is
put into the water and allowed to remain for a certain length of time.
When the seed is taken out, more or less of the germs remains on each
kernel, and when it is put into the ground the germs keep on working,
making nitrogen which the growing plant absorbs. It is wonderful to see
the effect in a field where one row has these germ-infected seeds, and
the other rows are not so treated."

It was now May, and the weather was slightly cooler, but there was
neither snow nor frost. North of the equator it was growing warmer,
because the winter had passed. Here the summer had gone, and winter was
coming on. From every indication they were not in a cold climate.

"Why do you think we shall not have any snow?" was Harry's inquiry.

"I notice too many trees, as well as shrubs and flowers, which could not
live if we had frosts or freezing weather. Many of the trees about here
do not shed their leaves, and the kind of animals which we now know
exist here are sufficient evidence that we need not fear cold weather."

For more than a week the boys and the Professor put in their time
prospecting in the hills and in carting various ores and mineralogical
samples to their workshop.

The pelts which were on hand needed curing and besides there were also
four yak pelts which had to be tanned, as shoe leather was badly needed.
The hide originally dehaired was long ago ready for tanning, as well as
the later ones.

"What shall we use for the tanning process?"

"The bark of certain trees must be procured, so if you can find either
oak, hemlock, birch or beech trees, we can probably make a tanning
compound which will serve our purpose."

"In what way will the bark of those trees tan the leather?"

"All the barks named contain what is called tannic acid. Other elements
also are used, such as gallic acid, alum, sulphate of iron, and copper,
salt, and other agents."

"What are the chemicals for?"

[Illustratio