No. 2.—This must be seven and a half inches long, one and a half inches outside, and an inch inside.
No. 3.—This is a length of tubing about sixty inches long, two and a half inches in outside circumference, and at least an inch thick. If an inch and a half thick all the better, as it will be more air-tight.
Divide tube No. 2 into two equal parts, cutting from right to left at an angle of 45 degrees. Into one of the parts fit a plug of hard wood pierced lengthwise by a red hot wire (fig. 1); the figure shows the shape of it sufficiently. In the hollow side cut a small opening, and over this tie very tightly a band of flexible india-rubber (fig. 3). This band will serve as the valve of the piston of the pump. Figs. 3 and 4 give a side and front view of this valve. Great care must be taken neither to split the plug in boring the hole nor to cut the tube.
Fig. 3.
Fig. 4.
This valve must now be inserted in the large tube No. 1, as seen in fig. 2.
At the other end of the large tube, which will serve as the body of the pump, at B fig. 2, fix a similar valve to the above, but the india-rubber band must be fixed on the other side of the valve as at B fig. 2. The fitting A will serve for escape, the second for withdrawing the air from the space to be exhausted. Finally fix tube No. 3 on valves A or B, fig. 2, according to your wish to produce a vacuum or to compress the air.