daddy blake and the two children glided to and fro over the ice of the frozen lake on their sharp steel skates. soon all their cheeks were red and rosy, and they felt as warm inside as though they had taken some hot chocolate at the corner drug store.

"daddy," asked hal, "what makes you warm when you run fast, or skate?"

"it is because your heart pumps so much more blood up inside your body," explained daddy blake. "our blood is just the same to our bodies as coal is to a steam engine. the more coal the fireman puts under the boiler (that is if it all burn well, and there is a good draft) the hotter the fire is, and the more steam there is made."

"is our blood like steam?" asked mab, as she tried to peep down at her red nose and cheeks. but she could not see them very well so she looked at hal's.

"well, our blood is something like steam," said daddy blake, with a laugh. "that is if we didn't have any blood we could not move around, and live and breathe, any more than an engine could move if it had no steam.

"you see we eat food, which is fuel, or, just what coal and wood are to an engine. the food is changed into blood inside our bodies, and our heart pumps this blood through our arteries, which are like steam pipes. our heart is really a pump, you know; a very wonderful pump."

"my heart is pumping hard," said hal, putting his hand over his thumping chest.

"well," went on his father, "the reason for that is, that when we run, or skate fast, our body uses more blood, just as an engine which is going fast uses more steam than one going slowly. the heart has to pump faster to send more blood to our arms and legs, and all over, and whenever anything goes fast, it is warmer than when it goes slowly.

"if you rub your finger slowly over the window-pane, your finger will not be very warm, but if you rub it back and forth as fast as you can, your finger-tip will soon be almost warm enough to burn you.

"that is something like what happens when you run quickly. the blood goes through your body so much faster, and your heart beats so much harder, trying to keep up, that you are soon warm. and it is a good thing to exercise that way, for it makes the blood move faster, and thus by using up the old blood, you make room for new, and fresh.

"but i guess we've had enough talk about our hearts now," spoke daddy blake with a laugh. "we'll eat some lunch and then take home our fish."

daddy blake built a little fire on the shore, near the frozen lake, and over this blaze, when the flames were leaping up, and cracking, he heated the chocolate he had brought. then it was poured out into cups, and nice chicken sandwiches were passed on little wooden plates.

"isn't this fun!" cried mab as she sipped the last of her chocolate.

"indeed it is," agreed hal. "i'm coming skating over to this lake every day!"

"well, i guess not every day," spoke daddy blake with a smile. "but we'll come as often as we can, for i want you to learn to be good skaters. and besides, there may be snow soon, and that will spoil the ice for us."

"oh, i hope it doesn't snow for a long time," sighed mab.

"so do i!" echoed her brother. "but, if it does, we can have some other fun. daddy will take us coasting; won't you?"

"i guess so," answered mr. blake.

the lunch things were packed in the basket, and then hal and mab went back to where the pickerel fish they had caught were left lying on the ice.

"why, they're frozen stiff!" hal cried, as he picked up one fish, which was like a stick of wood.

"that shows you how cold it is," said mr. blake. "but mamma can thaw out the fish by putting them in water, and we can have them for dinner to-morrow."

"when are we coming skating again?" asked hal as they were on their way home.

"oh, in a few days," his father promised. "meanwhile you and mab can practice on the pond near home, and then you can have a race."

"oh, good!" cried mab. "and i'll win!"

"huh! i guess not!" exclaimed hal. "boys always win races; don't they,

daddy."

"well, not always," said mr. blake. "and mab is becoming a good little skater."

"well, i'll win!" declared hal. "you see if i don't!"

the next day was too cold for the children to go skating with their daddy, but a little later in the week it was warmer, and one afternoon, coming home early from the office mr. blake said:

"come on now. i hear you two youngsters have been practicing skating on the pond, so we'll go over there and have a race."

"hurray!" cried hal.

"oh, i do hope i win!" exclaimed mab.

there were not many other skaters on the ice when the children and their father reached it mr. blake marked off a place, by drawing two lines on the ice with his skate. the space between them was about as long as from the blake's front gate to their back fence.

"now, hal and mab," said daddy blake, "take your places on this first line. and when i call 'go!' start off. the one who reaches the other line first will win."

hal and mab took their places. they were so eager to start that they stepped over the line, before it was time.

"go back," said daddy blake, smiling. finally they were both evenly on the line. the other skaters came up to watch.

"go!" suddenly cried daddy blake.