Ishaw-henry] 



SIMPLE PERIODIC CURVES 



147 



30 H es: 



Figure 4 



angles 6 = 9° and = 50° 30 ; while from b to c the projection was 

 obtained with the angles ^ = 13° and = 44° 50 from the projection 

 of a sine curve with A = 2 • 5 cm. and r = • 84. In the figure the scale for 

 1 hour corresponds to -53 cm. in the original copy of the projection. 

 By varying r other fair adjustments could be obtained. 



In Fig. 4, however, we have a satisfactory and remarkable agree- 

 ment. The Levis curve of Fig. 3, has been projected into the curves 

 for other places higher up the St. Lawrence, and it has been projected 

 successfully as a whole, the angles being the same for each tide. In 

 curve (a) of Fig. 4 the continuous line represents the projected Levis 

 graph, at 6 = 1° 45 and = 34°, while the dotted line represents the 

 actual record at Platon^ on the same day. 



In (è) the continuous line shows the projection of the Levis curve 

 at = 55° and = 2°, while the dotted line gives the correct graph for 

 Richelieu^ on the same day. 



Similarly in (c) the continuous line gives the Levis record after 

 projection at = 75° and 0= 10°, while the dotted line gives the actual 



' Platon, Richelieu and Cap à la Roche are respectively 30, 40 and 50 miles 

 approximately, above Levis. 



