06 Proceedings of the Royal Society of Edinburgh. [Sess. 
5 -6k 
4-5 
3-4k 
sl 
\ 
r 
N Y 
1 
sl 
' x 
+t?r>b. ^ 
< 
7^"* 1 
\ 
s of isobars and isotherms 
£ 1 J 1° — \Ktlomtbss 
scale, of wind velocity 
9 20 3 ,° 
J I 
7/ieCeo per second 
2-3i 
1-2 
0-1 
Fig. 4. — Pilot balloon sounding, April 29, 1908. North-west wind over south- 
west : characteristic of an advancing depression. 
The arrow shows the direction and velocity of the wind ; the full line, the position of 
isobar next above that which passes through the station. The dotted line through the 0 
shows the isotherm passing through the station ; the parallel dotted line, the isotherm 
for one degree higher than that of the station. 
