“Now, all that grass is spoiled,” said Rollo.
“O, no,” said Jonas; “it hasn’t hurt the grass. It has only burned the dry tops and the weeds. The roots of the grass are all safe, and the ashes left by the fire will make them grow all the better next summer.”
“Then, Jonas, let’s burn the ground all over.”
“No,” said Jonas; “if so large a surface gets on fire, we can’t stop it, till it runs into the fence, and sets that on fire,—or else gets over into the other field.”
So saying, Jonas pointed to a large level field or pasture over the fence, where the grass and weeds were much higher than where they were. The grass and weeds in this other field extended back some distance to a piece of woods; and Jonas said that, if the fire got into the woods, he could not tell how far it would go, or what mischief it would do. “So you see we must be sure and not let the fire get away from us,” said he.
Just then, Jonas saw that the fire was beginning to spread from another of the heaps; and he went to it to watch it. He said he was going to let it run a little way before he put it out, for he knew that if a piece of the ground around the heap was once burned over, the fire would not spread again from the heap.
So he waited, and, when the circle from that heap had become as large as he wished, he and the boys whipped it out; and then they went back to the first fire, which was now getting beyond the thistles, so that they whipped that out too. Rollo and James felt much relieved, now that they perceived that, by the aid of their fir-branches, they had the fires so entirely under their control.
About this time, Rollo saw his father coming through the trees, on the other side of the brook. His father had been a little afraid that Jonas would get into difficulty with his fires, and had come out to see. He found, however, that Jonas knew how to manage the business. He took a branch, and began to help the three boys whip the fires, as fast as they spread beyond the limits which they concluded to allow them.
“I didn’t know that the grass would burn so before,” said Rollo.
“It will not,” said his father, “unless it is both hot and windy. This is an illustration of what I explained to you the other day. When grass is heated above a certain point it takes fire. Now, when one blade of grass is burning, it does not usually produce heat enough to raise the next one to such a degree of heat that it will take fire; but this afternoon it will; for now the heat of one little tuft burning is enough to heat the next one sufficiently to cause it to take fire, because it is already partly heated by the sun.”