earth for normal human pulses between seventy and eighty beats per minute yet this rhythm valets every time we move or change position it's like this when we are resting like there is when we are running or at play and changing to with our emotions when we are happy and angry or frightened listen what do you hear now human heart your watch is a power plant that must operate unfailingly under an infinite variety of conditions and yet unlike our heartbeat the beat of this tiny power plant must age unlike the giant generator that has no tons of concrete on which to rest solid level and sleep from vibrations which might affect its accuracy there are no logical attendan lol careful drivers low skilled pilot know banks of instruments and controls to regulate its speed and guard its accuracy to understand what goes on inside a watch let's make a simple device that will keep time and will use a garden hose first will place a little water wheel and dial in the center when water passes by opening the nozzle wider we allow a heavy stream of water to flow through the hose and the hand on the dial turns faster if our source of power the water pressure remained constant and if we could adjust the nozzle carefully enough we would have a time piece that would keep accurate time it's here in a greatly simplified form we have the four elements needed in every time piece our source will begin with this part the main spring and bottle assembly and so we can see everything that goes on inside let's use giant parts to make a watch model this is the mainspring and it lives inside the mainspring barrel it's the mainspring is the power plant of the watch but source of power like the faucet in our water block by winding the spring we can store up energy here is a winding stem with gears and a click to keep the spring from unwinding and here is the unit that controls the flow of power like the nozzle on our hose it is called the balance wheel and hairspring assembly it consists of the balance wheel hairspring balance staff or axle fastened to the balance staff is a part called a roller now to the power across arm we add up our jewel shaped like this or use the energy stored up in our name spring to drive the escape wheel as the mainspring on coils it causes the barrel to rotate with it that didn't last long did it let's try it  once things get started there's nothing to stop them what we need now is a way of holding the power in check releasing it our little at a time and just when it's needed another power gen at the other end of the power cross  until the escape wheel is again unlocked but when we connect the mainspring directly to the escape wheel the power is soon exhausted in an actual watch it would last only a few seconds but we need is a way to stretch the power so it will last for more than a day in our water clock we use the hose to transmit power from the faucet to the nozzle we also need a way to transmit power here so let's add a system of will stretch them out in the line instead of in their usual closely confined location in a watch look at the gears a moment and see what they do a partial revolution of the center wheel drive the third wheel a complete enough to last a full day and longer energy from the mean spraying back and for the balance wheel swings controlled by a small coiled spring the hairspring imperfect rhythm each swing unlocks the escape wheel so it can give an all we have to do now to measure time is current that takes but this would be a tedious job and not very practical just as we needed a dial on our water clock here too we need a method for recording the flow or power so to the shaft of this gear or wheel we add an indicating hand to measure seconds as the gear train of a watch which is just the right size so about it turns one complete revolution while the second hand makes sixty revolution and to copy ours we can have another pointer geared just so to move one complete revolution every twelve hours now we can tell what time it is but again a train or a strong nod like this is a long way from an actual watch let's let our model do a bit of rearranging all by itself with incredible accuracy but the basic principles are those we have just seen frequently applied on a scale almost microscopic to produce the rounds most accurate about measuring instruments in a truly fine watch there are many things which make possible the accurate control and release of power jewels for example many people correctly believe jewels increase the value of a watch they increase the value of all right but not by being on a mental jewels are in a large strictly for business they add to the value if only when correctly placed a these tiny services are finished so smoothly they reflect images like a camera lens and working with oil it takes a drop no larger than a pinhead for the entire watch there is almost no friction final watch the hairspring has uniform thickness throughout its whole range is polished to a mirror like finish and made of metal relatively unaffected by magnetism or changes in temperature knife like edges of the instrument which checks it with perfect poising and without error springs centered on the balance wheel it runs accurately in any position all right time and it's the same with all the parts but tiny screws scarcely larger than a speck of dust the exceedingly small shaft precisely made gears and pinion mikkel silver plates and bridges every part is made with most precision precision which approaches perfection when we look at the almost invisible parts understand what they are wonderful mechanism with that you can accurately measure the passing of time and record data passing for your use and convenience but this mighty little servant is a creation of beauty to