1889-90.] . SCIENTIFIC TIME RECKONING. 229 



with our preconceived notions and habits of thought. The Hour Zone 

 system is introduced as an easy means of transition from old to new 

 ideas and it is found that by adopting Hour Meridians as local stand- 

 ards for reckoning, grave difficulties are in a large measure overcome 

 without any violent departure from our inherited usages and prevailing 

 customs. The hour zone system also furnishes the means of applying 

 the correct principles of Universal time in ordinary affairs. 



13. In the Hour zone system the circumference of the Globe is 

 divided into twenty-four sections or zones. The central line of each 

 zone is an hour meridian, and the hour meridians are fifteen degrees of 

 longitude apart. The accompanying chart of the world on Mercator's 

 projection shows the geographical position of the twenty-four hour 

 meridians. They are numbered in consecutive order towards the west 

 from zero, the anti-prime meridian. 



14. The Hour zones theoretically extend seven and a half degrees of 

 longtitude on each side of the hour meridians, but in practice that is by 

 no means an essential rule. The boundary line of contiguous zones may 

 be governed by national, geographical, or commercial circumstances. 



15. As the earth rotates on its axis in twenty-four hours an hour 

 elapses between the solar passage on each successive hour meridian, it 

 is obvious therefore that if the reckoning in each zone be governed by 

 its respective meridian, the reckonings everywhere will be directly 

 related. There will be differences but the differences will in every case 

 be known and they will invariably be multiples of an hour. Through- 

 out the Globe there will be complete identity in the minutes and seconds. 

 For example when the reckoning in the tenth zone is six hours twenty- 

 five minutes, in the eleventh zone it will be five hours twenty-five 

 minutes, in the twelfth zone four hours twenty five minutes, and so on, 

 each successive zone differing by an exact hour. Thus the only 

 departure from complete uniformity in reckoning around the Globe 

 will be in the numbers of the hours, but the numbers of the hours 

 being governed by the numbers of the hour meridians, the passage 

 to Universal time is simple and direct. 



16. As the reckoning in the zone of the twelfth hour meridian 

 corresponds with Universal time, the reckonings in all zones to the East of 

 that meridian will be one or more full hours in advance of Universal time, 

 and in all zones to the West of the twelfth hour meridian the reckonings 

 will be behind Universal time. Universal time will be the mean of all 

 possible reckonings under the hour zone system, and the Universal day 

 the mean of all possible local days. 



