SOME BEMAEKS ON 
203 
anemometer of the second of the above classes^ in which a square 
board is made to turn by a weather vane so as always to face 
the windj and the record is kept by means of a lever moving a 
pencil to a distance corresponding to the pressure, over a sheet of 
paper actuated by clockwork* This instrument-™described in 
various publications^— -after the expenditure of much time and 
money, was at last brought to a very perfect state, and has 
superseded all other pressure anemometers, wherever such 
instruments are used. 
But, beside the want of self-registering instruments, there 
is another -reason given for the small progress in Meteorological 
results, viz., the long continued mistake of seeking to determine 
the elements direction and pressure, instead of direction and 
velocity. This is not easy at once to understand, for there 
can be proved to be a direct relation existing between pressure 
and velocity of the wind, of which the most simple and easily 
remembered expression is that given by Mr. Hawkesley at the 
recent meeting of the British Association at York — 
when = pressure in lb. per square foot, 
'y = volocity in ft, per second. 
But though it is true, as stated by a writer in Enc. that, 
owing to the want of uniformity in the motion of the air, the 
relations between these two quantities are practically much 
more complex ; yet, if the actual pressure were obtained, the 
velocity would be approximately deduced, and the real question 
appears to be rather as to the possibility of obtaining a correct 
record of pressure. For the meteorologist who requires the 
velocity, there can be no hesitation as to the choice between the 
^ British Association Eeport, 1844. 
2 Vol. II., p. 24., Ninth Edition, 
