"About half a minute, Mr. Rennie says. He watched one of these little creatures, and found that she was building on the inside wall of a coal-house, where the bricks and mortar were left rough: she was at work between two of the bricks where the mortar had fallen out, or where the bee had taken it out. And the conduct of the bee at her house was very different from what it was at the clay-bank. She was not frightened, but went on working when any one came near the clay-bank; but at her house she seemed afraid that it should be found out where it was. She would alight first on the roof outside, as if she merely wished to rest herself; and when she flew into the coal-house she would not go directly to her nest, but would settle on a shelf, and sometimes pretend to be examining a great many places in the wall between different bricks; and at last, when she supposed there was no risk, or when there was nothing to alarm her, she would fly to her nest, and go to work with all her might in fixing her piece of clay to the wall." "Why did she wish her house not to be found out, Uncle Philip?" "Mr. Rennie supposed it was her instinct: she had seen probably some of the insects which would destroy her young, watching her to see where she was building; and sometimes after flying nearly to her nest with a load, she would turn back and fly towards the clay-bank, or take a large sweep off in another direction, and so come to her house. "Besides the mason-bee, boys, there is the mason-wasp, which I have heard some persons call the _dirt-dauber_: it is very common, especially in the southern part of the United States. It works very much like the mason-bee, only it is apt to fix its nest under the eaves of old houses, which I think the mason-bee never does. "There is also another kind of mason-wasp which will actually break a hard brick. Mr. Rennie says that he saw one at work on a brick of a hard yellow kind. Whether the wasp found a hole in the brick to begin with, he did not know; but if he did he was hard at work making it larger: he would break off a piece as large as a mustard-seed at a time. Here is a drawing of that kind of wasp; and the insect is no larger than the picture. [Illustration: Mason-wasp.--Natural size.] It seems wonderful that so small an insect should have so much strength. Here is a picture of its jaws, seen through a microscope, so as to appear a great deal larger than they really are. [Illustration: Jaws of Mason-wasp.--Greatly magnified.] "I do not know, boys, that the masons we have been talking of, show us any _tools_ like those with which men who are masons work; but they show us, at any rate, how to make mortar by kneading or working it together; and they certainly show us that we were not the first who built walls. But there is another kind of mason who works in stone. He picks out the stones which are of proper size, and he fastens them together with mortar really as men do." "Pray tell us of him, Uncle Philip."