"It makes it, boys. This kind of bee may be seen flying about, picking up sand, grain by grain, putting it into a heap, gluing them together with a sort of gum out of her own mouth, and building with them a foundation for her house. This little workman commonly builds against the side of a wall between two bricks where the mortar has fallen out; and if you should see one of the nests, it appears exactly like a lump of dry mud which has been thrown wet upon the wall out of a cart-rut: but when you examine it closely, you may see a great many small stones in it, more than is common in mud: a hundred people, though, might pass by it, and never think it was any thing more than a lump of dirt, which had been thrown upon the wall when it was wet, and had afterward dried there. Here is a picture of one of these nests. [Illustration: Exterior wall of Mason-bee's Nest.] You see there is a small hole in it; this leads to a cell inside about an inch deep, and shaped exactly like a lady's thimble; the inside of this cell is polished smooth, and appears like a wall of plaster, except that it has little yellow stains upon it. Here is the bee that makes it. [Illustration: Mason-bee.--Natural size.] In making this mortar to build with, the bee will sometimes add earth that is soft to its grains of sand, and when the lump is about the size of a small shot, it takes it up and flies away with it, to work it into the wall." "Does it always use sand, Uncle Philip?" "Not always: sometimes it takes wet clay, and will dig into a bank of clay baked hard by the sun on the outside, so as to get that which is wet. "Mr. Rennie, a gentleman in England who is very fond of watching insects, and has found out a great many curious things about them, has given an account of some of these bees which he noticed at work. Every one was carrying out of a hole in the clay-bank a small lump of clay; and on catching one of them, he found that this lump was wetter than the clay in the hole, so that the bee had moistened it, and worked it together, to make it stick like good mortar. These lumps too were larger than a shot; they were as large as a garden-pea." "How long did it take them to work up the lump?"