“He spoke of the bridge of boats across the river, and said she would enjoy watching it open and shut to let the steamers and big rafts pass through.  And he told of the Cologne water that is sold in so many of the shops.  It is hard to tell which makes the town most famous, the great cathedral or the Cologne water.”

“Father, how was the bridge of boats made?” asked Bertha.

“The boats were moored in a line across the river.  Planks were then laid across the tops and fastened upon them.  Vessels cannot pass under a bridge of this kind, so it has to be opened from time to time.  They say it is always interesting to see this done.”

“Yes, Frau Braun said she would rather see the bridge of boats than anything else in the city.  She has already begun to plan how she can save up enough money to make the trip.”

“I will go over there to-morrow to see her new necklace,” said Bertha.  “But what is amber, father?”

“If you should go to the northern part of Germany, Bertha, you would see great numbers of men, women, and children, busy on the shores of the ocean.  The work is greatest in the rough days of autumn, when a strong wind is blowing from the northeast.

“Then the men dress themselves as though they were going out into a storm.  They arm themselves with nets and plunge into the waves, which are bringing treasure to the shore.  It is the beautiful amber we admire so much.

“The women and children are waiting on the sands, and as the men bring in their nets, the contents are given into their hands.  They separate the precious lumps of amber from the weeds to which they are clinging.”

Their father stopped to fill his pipe, and the children thought he had come to the end of the story.

“But you haven’t told us yet what amber is,” said Bertha.

“Be patient, my little one, and you shall hear,” replied her father, patting her head.  “As yet, I have not half told the story.  But I will answer your question at once.

“A long time ago, longer than you can imagine, Bertha, forests were growing along the shores of the Baltic Sea.  There was a great deal of gum in the trees of these forests.  It oozed out of the trees in the same manner as gum from the spruce-tree and resin from the pine.

“Storms arose, and beds of sand and clay drifted over the forests.  They were buried away for thousands of years, it may be.  But the motion of the sea washes up pieces of the gum, which is of light weight.

“The gum has become changed while buried in the earth such a long, long time.  Wise men use the word ‘fossilized’ when they speak of what has happened to it.  The now beautiful, changed gum is called amber.

“There are different ways of getting it.  I told you how it comes drifting in on the waves when the winds are high and the water is rough.  But on the pleasant summer days, when the sea is smooth and calm, the men go out a little way from the shore in boats.  They float about, looking earnestly over the sides of the boats to the bottom of the sea.