NO. 7.] DECLINATION. 19 



PI. I XVII. In the case of every series of observations, I have placed the 

 deviations from the lowest value of the day in column D, or in column M, 

 as ordinates according to the scale 1 10 mm., so that every millimetre is 

 equal to 6', while the hours are marked as abscissae according to the scale 

 l h = 10 m.m. As the observations were only taken in the daytime, the time- 

 scale extends only from 9 a. m. to 9 p. m. 



