The last days of October were cold and windy and it seemed as if the north wind drove all wild birds before it. Thousands of robins and little yellow-patched birds, the hardy myrtle-warblers, filled the timber on the river islands. Long dark clouds of different kinds of blackbirds passed southward, great whitish gulls came drifting along from somewhere, and the black terns, dull colored in summer, had donned their white autumn plumage.
“I believe I saw 500,000 ducks to-day,” said the trapper as he returned to camp one evening with all the mallards he could carry.
“The birds are going fast, and it will soon be winter. We must cut a lot of wood and pull our boats up to a high place, so they will not freeze in. These woods may be under water next spring and we may need our boats in a hurry.”
Early in November came one of those cold rain-storms that mark sharply the end of Indian summer which often prolongs the warm season far into autumn.
It was the first day that all four campers stayed in the shack, which the trapper and the Indian had during the preceding week transformed into a real cozy cabin. Chunks of ash, elm, maple, and cottonwood slowly burning in the old sheet-iron stove which Barker had set up in the middle of the room kept the cabin dry and warm, while the large spattering drops of rain beat a tattoo on the roof.
The few stray leaves that had until now adhered to their branches were swept away. The river-bottom trees assumed their sharp, undraped silhouettes of winter, and from the bluffs all the bright autumn colors had vanished.
The summer birds had gone. Only a few hardy chickadees, woodpeckers, and nuthatches that defy even the coldest northern winter had remained behind the migrating hosts.
By the middle of November the lake was frozen over.
With the beginning of cold weather little Tim’s health rapidly improved. Soon he was strong enough to go sliding on the ice; and when Barker had a blacksmith at the landing make a pair of skates for each of the boys the joy of the lads was unbounded.
They skimmed lightly over the frozen sloughs, where the trees and banks sheltered them from the wind. From these trips they returned with flushed cheeks and ravenous appetites and many stories of what they had seen.
They had chased pickerel and other fish under the clear ice, they had seen a muskrat swim along with an air bubble attached to his nose, and they had watched clams slowly plowing their furrow in the sand as they withdrew from the shallower banks into deep water.
The Mississippi and its tributaries harbor a large variety of clams whose shells are now used for pearl buttons. The boys were curious about the habits and life of these quiet creatures that were always nearly buried in mud and sand and moved about by queer little jerks. When Tim was still too weak to move about much, he had amused himself for hours dropping clams, which Bill had caught, back into the water, and watching how each shell, slowly opening, put out a sort of white, fleshy foot; slowly righted itself, and crawled away into deep water.
“What do clams eat and how do they spawn?” the boys wanted to know, but on these questions neither trapper nor Indian had any information.
Clams do indeed lead a strange life. They cannot run after their food, so they just open their shells a bit to allow the water to run through, in order to catch any small particles of food the water may contain.
The young clams just hatched are so small that the naked eye can scarcely see them. They have no shell at all and swim about very actively. As soon as possible they attach themselves to the gills of several kinds of fish. The fish do not like it, but they have no way of escaping from the very minute creatures. Embedded in the gills of fish the young clams live for some weeks looking like small pimples. When they have grown a tiny shell they drop to the bottom of the river or lake and begin to live in the usual way of clams. That is the curious life-history of the river clam.
While the skating lasted the boys were well occupied. The............