198 Proceedings of the Royal Society of Edinburgh. [Sess. 
Weir’s azimuth diagram does to the (4.0) one. Instead of the A-scale 
(x = 1, y = — cos A) there has been substituted the scale on the circle 
x 2 -\-y 2 — 1 given by the radial line through the origin to this A-scale. 
When one arm of the ruler joins the point a on the u-scale to the point 
( b , c) in the network, the other arm, when made to pass through the origin, 
cuts the circular A-scale in the required value of A. 
This modification has the advantage over the original of being only 
half its size for a given accuracy, and of avoiding some of the excessive 
compression which occurs near where b and c approach the value 90°. 
We could project the a - scale of d’Ocagne’s nomogram to infinity 
instead of the A one by a similar transformation, but it does not seem to 
offer any special advantages. 
(Issued separately November 29 , 1916 .) 
