743 



MR J. D. HAMILTON DICKSON ON 



transparent celluloid scale, having a straight line marked on it, and it was adjusted until 

 this line fairly coincided with the points ; no point was farther from the line than the 

 width of the pencil-point mark making the point, say half a mm. Readings of the 

 points on this line were taken from the millimetre paper, at a distance of some 760 mm. 

 apart, so chosen that the numerator of the tangent of the required angle should be an 



fl, 



r 





O * 



\)B 



/ 



1 / 



/ 



/ 

 i / 

 ■ i 



1 i 





Fig. 5. 



exact number of centimetres of convenient length (it was 5 cm.). These points were 



756 

 T=178, H= -206, and T=128, H = 550; hence cot *> = — - = 1512, a result agree- 



ing well with 15*20 measured from the earlier diagrams. 



A fresh calculation, similar to that already described, but with the new value of 

 tan a>, was made, and gave these results — 



ith 



a = 118-6492, 

 k = 312-7536, 

 p= 89-9627, 



(21) 



\v 



leading to 



tan to- 



1 



1512 J 



whence 



the equation of the Tait-line. 



1,022,522-48 -3024-0 +111895-00^/0: 

 where 6 = t + 420-6684 



dE onnA .11189500 



(22) 

 (23) 



(24) 



