386 Proceedings of the Royal Society of Edinburgh. [Sess. 
XXIII. — Proposals for an Anemometer and a Portable Barometer. 
By J. T. Morrison, M.A., B.Sc., Professor of Applied Mathematics, 
Victoria College, Stellenbosch, Cape Colony. 
(Read January 10, 1910. MS. received January 14, 1910.) 
A. An Anemometer that will register separately the North- 
Southerly and East- Westerly Components of the Wind. 
1. The Object of the Instrument. 
For many important meteorological purposes it would be an advantage to 
be able to keep separate records of the components of the wind in two 
fixed rectangular directions, the north - southerly and east - westerly 
directions being those that would naturally be chosen. At present the 
registering Robinson anemometer records merely the total amount of wind 
that has passed any spot ; a separate pen gives the direction ; and a some- 
what laborious process of calculation is needed in order to obtain even 
an approximate estimate of the wind-components. The object of the 
instrument described below is to resolve the wind into northerly and 
easterly components and to record their absolute values with two separate 
pens. The instrument is so arranged that the distance of the one pen from 
its zero line at any instant will be a measure of the excess of north wind 
over south wind which has flowed past up to that instant, and the curve 
traced by that pen will show all the variations of this north-southerly 
component. The slope of this curve at any point gives the velocity of 
the north component at the corresponding instant of time. The curve 
traced by the other pen gives similar information regarding the easterly 
component. The ratio of the two slopes gives the direction. In fact, as 
the recording cylindrical drum turns uniformly on its axis, the first pen is 
drawn along its surface in a direction parallel to its axis at a rate propor- 
tional to the northerly component of the wind, while the other pen travels 
at a rate proportional to the easterly component. If an easterly wind 
changes to a westerly, the corresponding pen travels backwards, and so on. 
2. The Principle of the Instrument. 
The distinctive part of the new instrument is that which analyses the 
wind-velocity, or rather which analyses a rotation proportional to, and 
