202 
THE METHODS OF WIND MEASUEEMENT. 
before this, there had been numerous wind pressure guages 
invented, which have been divided by Dr. Eobinson into four 
classes. 
(1) Windmills kept facing the wind and winding on their 
axle a string against some form of graduated resistance. 
(2) Spring pressure boards, also kept facing the wind, and 
acting somewhat as an ordinary spring weighing balance. 
(3) Tubes in which a difference of level of a liquid due to 
different pressures could be seen. 
(4) Pendulum anemometers, in which the extent to which 
the pendulum was swung out of perpendicular against the 
action of gravity by the force of the wind gave approximately 
the pressure. 
Besides these, there were the musical anemometer of Dr, 
Hooke, which recorded the velocity by the pitch of the note 
emitted, and those of Leslie and Brewster, in which the rates of 
cooling and evaporation were respectively used to give the 
quantity. 
Quite recently a pressure anemometer has been described^ by 
C. H. Hagemann, in which the pressure of wind acts on a 
column of air, and is registered on a dial by an apparatus not 
unlike a gasometer in principle. 
But the comparatively unfruitful result from these instru- 
ments, in spite of the existence of the tables of Eous, Smeaton, 
and Hutton, were no doubt chiefly due to their being non- 
recording — a defect which, in consideration of the uncertain and 
changeable nature of the wind, is obviously fatal, for nothing less 
than a continuous record can be of use for accurate scientific 
purposes. 
About the year 1837, a self-recording instrument was 
invented by Mr. Osier, of Birmingham. This was a pressure 
Quarterly Journal Meteorological Society, Oct., 1879. 
