xtracted from the leaves, and is
used for medicinal and other purposes. It is said to be very
objectionable to mosquitoes, and Harry was told that if he scattered a
few drops of eucalyptus oil on his pillow at night, he would not be
troubled with mosquitoes, even though there might be many of them in the
room. He promised to try the experiment at the first opportunity.

Ned asked what variety of the eucalyptus was the tallest, and how tall
the highest tree of Australia was.

"The giant gum, _Eucalyptus amygdalina_, is said to be the tallest tree
in the world," the gentleman replied. "I am not sure whether it is
really so or not, as you have some very tall trees in the United States,
and there are also some of great height in the valley of the Amazon
River. I have heard of giant gum trees five hundred feet high, but their
location has always been given very vaguely, and nobody knew by whom
they had been measured. There is one giant gum tree on Mount Baw-Baw, in
Gippsland, that has been officially measured by a surveyor and found to
be four hundred and seventy-one feet high. What its diameter is at the
base I am unable to say, but probably it is not less than fifteen or
sixteen feet. New forests and new groups of trees are being discovered
from time to time, and perhaps we will one day find a tree more than
five hundred feet high.

"I will add," said their informant, "that the giant gum is also called
the 'silver stem,' because when it sheds its bark every year the new
surface of the tree, when the old one has come off, is as white as
silver. A group of these trees is a very pretty sight, as the trunks are
perfectly round, and very often the lowest limbs are fully two hundred
feet from the ground."

CHAPTER VI.

AUSTRALIAN BLACKS--THROWING THE BOOMERANG.

"Those giant gums are not easy to climb," Ned remarked, as the gentleman
paused.

"Not by any means," was the reply; "at least, not for a white man, but
the black fellow will climb one of them, or any other tree, with very
little trouble."

"Why, how does he do it?"

"He cuts notches in the trunk of the tree where he can place his feet,
and he goes on cutting notch after notch as he ascends, making a broad
spiral around the tree until he reaches the limbs. Sometimes he passes a
piece of rope, made out of twisted bark, around the body of the tree to
steady himself, but he is just as likely to take no rope along, and
trust entirely to keeping his balanc