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PALS a Rene CLONE ISS Re Pr gt See ey TSN ETAT GER SY 5 The -first meridian on the earth passes 'through Greenwich, England. Greenwich is a suburb of the city of London. The Royal Observatory is situated there and all figures and cal- culations used in the Nautical Al- manac are figured by time shown at Greenwich, We now show a cut of the earth as she would appear marked off in parellels of latitude and meridians of longitude--Fig. 21, The Equator is the starting point for latitude and the deep black line shows the first meridian of 'longitude. The great lakes are between latitude 40 and 50 north and between 75 and 95 west longitude. You will notice that parallels of 'TAE Marine Review 'time. Sun time is time. shown by 'the sun. When the sun is*/exactily 'on your meridian (on the north and south line that passes through' where you stand) it is then noon by sun time. But it can't then be noon at any other place. If you were at Cleveland at noon by sun time it is past noon at Fairport and not yet noon at Lorain.. The sun in traveling west takes noon with it wherever it goes. So every place east or: west will have a different sun time. Sun time used to be the only time used but when railroads began to cut through: our country this sun time was found very inconvenient. How could time tables be made where every city b 2 I) II L Hp oa a Cee SK SS a SS SS LA KS Ls WX Fic, - Zh latitude are the same distance apart for their whole length. But meri- dians of longitude are farthest apart at the equator and gradually come together at the pole.. One degree of latitude is €0 nautical miles every- where. A degree of longitude is 60 nautical miles at the equator, but only about 42 nautical miles in the region 'of the Great Lakes. Now, as we have said before, we have to know what. latitude is in order to find the latitude of our ship as is required to find the azimuth in the book. But we do not have to know the longitude of our ship to get an Azimuth. However, as there is a connection between time and longitude we have also told you what longitude is. While longitude is still fresh in our memory we will take up the subject of time. Time, For taking bearings of the sun we must have sun time. But we carry a watch that shows either Central or Eastern Standard time and have to figure sun time from that. You might wonder why we do not carry a watch that is set to sun time and save figur- - ing. This would not be possible un- less you remained in one place all the had a detour time? In 1883 an agreement was made to make Stand- ard time. Instead of having a dif- ferent time at every city it wads de- cided to divide the United States and Canada into four sections with one time for every section. Beginning at the east side of the country the time was named, Eastern Standard time, then Central Standard. time, Mountain Standard time and Pacific Standard time. The country was divided as follows: ee "You 'will notice that four meri-_ 'dians pass through this map, One passes through each section. Now in -- 'choosing' a time to be used in these four sections' they .chose the time of these four meridians. Now to -- show -you the connection between time and' longitude. = <= nee - The sun's rays travel completely around the earth every 24 hours, As every circle has 360 degrees the sun then travels 360 degrees in 24 hours. This' is At) the- pate 98 aa degrees every hour. When the sun * is * directly: 'on the ~ first meridian (the meridian that' passes through Greenwich, England) we will start a clock. It is then noon by sun time. In'-exactly one hour the sun has traveled west and is directly over the 15th meridian.- In another hout it is directly over the 30th meridian and so on. Therefore every fifteenth -- meridian is called a standard meri- dian. Four standard meridians pass through the United States--the 75th, the 90th, the 105th and the 120th (see : standard time map). The time of these four standard meridians was chosen for the standard time to be -- used in the United States. As we said before, it is noon, by sun time, when the sun is exactly over the first -- meridian at Greenwich. "In exactly one hour'it is noon, by sun time on the 15th meridian. In exactly five hours from the time the sun left Greenwich it is over the 75th meri- dian and in six hours it is over the 90th meridian. The 75th and the 90th meridians pass through the region of the Great Lakes. The time of the 75th meridian is chosen for Eastern Standard time and the time of the 90th meridian is chosen for the Cen-. tral standard time. Now when it is noon by Central standard time the sun is exactly over the 90th meridian. K STANDARD TIME ; || BELTS 120 : 105