Arrange a siphon (Fig. 54), start the water flowing, and then pour sand or mud into the upper tumbler. Is the sand of mud siphoned over into the lower tumbler? [Illustration: FIG. 55 A SQUIRT BOTTLE ] Attach a long tube to the outer arm of the siphon and repeat the experiment. Is the sand or mud siphoned more rapidly and more thoroughly? Experiment 41. To make a squirt bottle. [Illustration: FIG. 56 SQUIRT BOTTLE IN ACTION ] Make a nozzle at one end of a piece of No. 2 tubing, make a bend near the nozzle, cut off the other end at such a length that it will reach to within ¼ inch of the bottom of the bottle, smooth this end, allow it to cool, wet the tube and the two-hole stopper, shove it through one hole of the stopper, insert an elbow in the other hole, and your squirt bottle is complete (Fig. 55). Fill the bottle with water, and blow through the elbow. Do you get a fine long stream from the nozzle (Fig. 56)? [Illustration: FIG. 57 TUBE FOR TRICK SQUIRT BOTTLE ] Experiment 42. To make a trick squirt bottle. You can have any amount of fun with a trick squirt bottle. It is exactly the same as the squirt bottle described in Experiment 41 except that it has a hole just below the bend (Fig. 57). [Illustration: FIG. 58 MAKING A SMALL HOLE ] To make the hole, make the long bent nozzle as in the last experiment, then heat the tube just below the bend in the blowpipe flame, touch a piece of glass tube to the red-hot glass (1, Fig. 58), and pull it away (2, Fig. 58). Do you find that the hot glass is pulled out into a thin pointed tube? Break off the thin tube close to the large tube, heat in the blowpipe flame until the edges are smooth and at the same level as the sides of the large tube. Flare the edges of the hole, if necessary; it should be about ⅛ inch in diameter. [Illustration: FIG. 59 TRICK SQUIRT BOTTLE ] Now fill the bottle with water, and blow hard (Fig. 59). Do you find that one stream of water is driven into your face and another out of the nozzle? Experiment 43. Fun with a trick squirt bottle. [Illustration: FIG. 60 TRICK BOTTLE IN ACTION ] Now to have fun with your trick bottle, show it to one friend at a time. Do not ask him to try the bottle, just go where he can see you and squirt a long stream, but unknown to him have your finger over the hole below the bend. [Illustration: FIG. 61 A SIMPLE ENGINEER’S LEVEL (_From Aldous’ Physics. Courtesy of The Macmillan Company_) ] Your friend will just naturally want to have a try at it. So you say “All right, let’s see who can squirt the longest stream.” Tell him that all he has to do is to take a deep breath and blow as hard as he can. He will do so, with laughable results (Fig. 60). Now together find another friend. Do not ask him to blow, but each of you blow as long a stream as you can, where he can see you. He will beg to be allowed to try, and finally you let him, with the same laughable results. [Illustration: