I06 BROWN : 



yearly motion ' " mean one and the same thing as far as visible 

 results go. The two ideas are interchangeable, and are so 

 treated in astronomical discussions. 



As we in this North Temperate Zone face the sun in the 

 South his yearly motion is from West to East, from our right 

 to our left "through the button hole " ; against the hands of 

 the watch which we hold before our face. The outward and 

 visible sign of this is the slow movement of the constellations 

 over toward the west. The daily motion is of course the 

 other way. 



One important use of mean solar time, it will be perceived, 

 is to save countless millions of people the intolerable and use- 

 less trouble of trying to understand the apparently irregtilar 

 motions of the true sun. 



And here I may remark that I have not attempted any 

 discussion of "dialling" or the draughting of the "hour 

 mai'ks ' ' ; for the simple and sufficient reason that I know 

 nothing, or very little about it. It is a somewhat intricate 

 matter. There are those that earn mone^^ by means of it ; 

 and those only find it worth their while to master the science. 



The difference of time between the arrivals at the meridian 

 of the mean sun and the real sun is called the " Equation of 

 Time." It is given roughly in the Almanac, for eveiy day in 

 the year ; and in the Nautical Almanac is set out down to the 

 hundredth part of a second. It is added ( algebraically) to 

 apparent time according to circumstances. 



That is to say. 



The expression " Clock Fast " is used to signify that the 

 true sun does not pass the meridian until after mean noon. 



The expression " Clock Slow " is used fo signify that the 

 true sun passes the meridian before mean noon. 



"Algebraically" means added with the proper sign, plus 

 or minus. 



And dial or apparent time is taken as the basis. 



So that we must add the equation with the plus sign to 

 dial tiiHL^ if the clock l)e fast. 



