Uncle George’s tank was very simple. It was made up of several large glass bells, such as the gardener uses for covering tender plants.
Each glass bell had a nob on the end of it. Uncle George got a large block of wood for each bell-jar. This block he hollowed out with a chisel.
He next bored a large hole in the centre of the hollow to hold the nob. Then he cut a piece of thick green cloth into a round shape, with a hole in its centre.
This piece of cloth was placed over the hollowed out part of the block, and the bell-jar, turned upside down, was placed in the block so that the glass nob fitted into the hole.
Uncle George fitted up four of these tanks and filled them with fresh water. The frog spawn was put into the first vessel. The next was for the newts. The third one held the caddis worms and some other curious creatures that had been found in the ditch.
In the fourth vessel were half a dozen pretty little fishes called stickle-backs, which the boys had caught in the brook.
Some water weeds and a few water snails or whelks were put into each vessel, except that with the frog spawn in it.
Every other morning Uncle George changed the water by means of a tube which he called a siphon.
This was a piece of lead pipe, about two feet long, and bent in the middle into the form of the letter U.
“The water weeds are very pretty,” said Frank.
“They are,” replied his uncle, “and they are also very useful. They help to keep the water pure. I should have to change the water every day if there were no weeds in it.
[Illustration: Stickle-backs, Pond Weed, etc., in Aquarium.]
“The whelks also are most useful. They are the road-men of our ponds and streams. They eat up all the waste matter, and so keep the water clean and healthy.”
It was great fun feeding those little fishes. They were fed sometimes on raw meat chopped very fine, sometimes on little pieces of biscuit. At first they were very shy, but they soon got over that. In less than a week they were quite at home, and would come up to the top of the water and take tiny pieces of beef from the boys’ fingers.
They would swim after Frank’s finger as he drew it round the tank, and would even leap out of the water for food that was held out to them.