![]() ![]() One tip, which applies to all homemade barometers try tomake your barometer on a day which is neither too wet and stormy (low pressure) or sunny and still (high pressure)If you pick a day when the air pressure is at about the middle of its range, then the if the water starts at aboutthe middle of the tube it will have plenty of room tomove as the air pressure changes. See if you can work out the reason for this - think about which lot of water is directly in contact with the outside air. Increased air pressure will make the liquid fall, decreases pressure will cause it to rise - the opposite to the homemade Torricellian barometers. Once the system has stabilized, changes in atmospheric pressure will cause the level of water in the tube to rise or fall. The air can't get back out, and the greater air pressure inside the bottle will force water into the tube. What you've done here is slightly increase the air pressure in the bottle by blowing air into it. You can add a scale or a ruler beside the tube to record changes in the water level. Once you can see water in the tube a fair way above the stopper, use the sealant or some other glue to prevent any air leaking through the hole in the stopper or around its edges. If not, check that everything is airtight and try again. If everything has worked properly, after you've blown some bubbles water should rise into the tube, hopefully well above the top of the stopper. Now comes the fun part - blow a few bubbles into the water. Make sure the end of the tube is below the water level. Insert the tube into the stopper and the stopper into the neck of the bottle. Partly fill the bottle with water and food coloring - a little over half full. It needs to be as airtight as possible, which is why we use rubber rather than cork. The hardest thing to do in the making of this device is to bore a hole through the centre of the rubber stopper and fit the straw or tube into it. You will need a narrow necked bottle, a rubber stopper, a clear straw or piece of plastic tubing (the longer the better), some flexible window sealant, some water and some optional food coloring. Nevertheless, weather glasseswere elegant instruments, and are still made today, mostlyas an ornament or talking point which actually does work. The Weather Glass, also known as a Water Barometer,was quite useful, but was an indicator of weather changerather than a measurer of air pressure - it was almostimpossible to calibrate one with another, and was affectedby evaporation of the water. ![]() It was relativelycheap, consisiting only of blown glass, and using only water,sometimes with other additives. It was called the Weather or Storm Glass, and was used by sailors, farmers, and otherswho needed to know what the weather was doing. Torricelli's barometer was the model for all mercury based barometers for the next two centuries, and providedan easy, if not always convenient way of measuringair pressure.īut at much the same time, a more simple method became popularfor predicting changes in the weather. Follow these links for information on What Is Air Pressure, somesimple Air Pressure Experiments, and the early History Of The Barometer. ![]() But such is often the way of science.īarometers measure air pressure and are one of the most important instruments used in weather forecasting. We'll forget that the original invention came by accident while he was investigatingthe production of a vacuum. In Part 2 of this series on How To Make A Barometer,you'll find how to make a barometer (actually two barometers)in much the same way that Evangelista Torricelli did whenhe invented the barometer in 1643. Make Your Own Water Barometer or Weather Glass ![]()
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