| Show BY THE STARS HOW TO TELL IF YOUR WATCH IS KEEPING PERFECT TIME few persons know perhaps that a watch may be more easily and more accurately regulated by a star than by the aun sun the reason Is that the motion of the earth with reference to the fixed stars Is perfectly uniform while with reference to the sun it Is not select a window opening on the south and giving a view of a chimney or of the side of a house to the side of the window attach a piece of cardboard with a little hole bored in it the card must bo be so placed that you can see a star through the hole watch the star as it approaches the chimney or the side of the house and note the exact time of its disappear disappearance behind it watch the ther same star the follows following ng night for the motion of the earth will cause it to disappear behind the chimney exactly 3 minutes and 56 seconds earlier than it did on the first night and that is what your watch will show it it be keeping accurate time let us its suppose that you saw raw the star disappear at 8 9 on the first night then on the second night it will disappear at 3 minutes and ar seconds before 8 it if you find therefore that the star disappears at three minutes before S on the second night according to your watch you will know that your baten has gained 56 seconds in the 21 24 hours it if it disappears at 4 minutes and 54 56 seconds before 8 your watch will have lost one minute if the sky eky be cloudy for say three nights after spur first observation so that you cannot see the star yo you u have only to multiply 3 minutes and 56 sec see onas by three and deduct the product from the time of your first observation to find the time that your watch should give it Is hardly necessary to say that you should use one of the fixed stars and not a planet as your our guide |
