e ought to study "railroading."

"Or laying pipes," Ned would tell him when Nat pointed out some
improvement in the miniature telephone system.

But Joe and Roger loved to watch their big cousin make the sparks and turn
on the signals, the latter task always being assigned to Roger, who had a
very small engine of his own to practice on.

"Come on, boys," said Nat to the youngsters, when, dinner being over,
Major Dale and his sister, Mrs. White, went to "figure out Christmas
secrets," and Dorothy turned to the piano to put in her time until the
hour for going out again, "come on, and we'll rig up something."

Instantly both little fellows were at Nat's heels, through the back hall
to the cellar-way, where Nat stopped to don his overalls, for he always
insisted that the first principle of true mechanics was "good, stout
overalls."

Nor were the clothes protectors unbecoming to Nat. In fact, he looked the
ideal workman, except he was not exactly of the muscular build, being
decidedly tall, and having such a crop of light, bushy hair.

"I'll show you how to make gas," said Nat as his two young cousins waited
impatiently to hear the program announced. "We can produce a very superior
article by the mere use of bark from a white birch tree, and a common clay
pipe. You cut the bark up into little pieces with a pair of scissors, fill
the bowl of the pipe, and then make a cover or plug for the bowl by using
clay or a mixture of salt, ashes and water. Stick the bowl of the pipe in
the stove or furnace like this," and he opened the door of the big heater;
"the fire causes the birchbark to give off a gas, it comes up into the
pipestem, and can be lighted at the end, thus--"

"What was that?" interrupted Joe. "A wagon outside?"

"Might be," admitted Nat, "but what's that got to do with making birchbark
gas?"

"I thought I heard some one call," apologized Joe, again taking his place
in front of the heater.

"There is some one calling," declared little Roger. "I just heard them."

"Well, I guess we had better give up the gas business," said Nat
impatiently, "and you kids might as well go out and interview the night
air." And with this he threw down the long-stemmed pipe, which broke into
a dozen pieces. Then, while the younger boys made their way back to the
kitchen, Nat started for the yard.

"My, it's cold!" he could not help exclaiming as he stepped out into the
clear, frosty air.

Then he brushed against something.