Academy of Science. 87 



A NEW METHOD OF DETERMINING THE WIND'S 



VELOCITY. 



By John H. Long, Class of '77, University of Kansas. 



It having been repeatedly stated by certain observers in Kansas that tlie ane- 

 mometer of the State University registered a higher than probable velocity, I was 

 induced at the suggestion of two gentlemen connected with the institution, to test the 

 correctness of the instrument. The apparatus used by me was veiy simple, consistmg 

 essentially of a hollow copper sphere suspended in front of a graduated horizontal 

 scale. But as a more detailed description may be necessary to the understanding of 

 what follows, I will give it here. Imagine first a perpendicular shaft of iron, eighteen 

 feet long, whose bottom fits into a socket and to whose top is attached a swivel. 

 To this swivel are fastened several wires whose other extremities are secured so as 

 to give complete steadiness to the shaft. Other braces are attached for the same 

 purpose, and the swivel on top permits it to turn to suit the varying direction of the 

 wind. A short distance below the swivel a horizontal arm, fifteen inches in length, 

 is firmly attached to the shaft, and just below this another oue is similarly attached. 

 These two arms are equal in length and parallel to each other. To the extremity of 

 the upper arm are fastened two fine iron wires, one, seventeen feet long, supporting 

 a plummet, and the other, six and a half feet long, supporting the copper sphere 

 mentioned above. This sphere is 8.5 centimetres in diameter, and weighs 135.92 

 grammes. To the extremity of the lower arm is attached the scale, consisting of 

 two lath-like pieces of wood, about four feet long, fastened parallel to each other and 

 about one-half inch apart. Between these, constituting a guide, the wires are sus- 

 pended, and on the front one the graduation is made. The plumb line serves to 

 determine the zero point, and is of no further use. By means of the swivel above 

 and the socket below, the apparatus is easily turned, so that when the ball is deflected 

 by the wind its vibrations may take place in the space between the two laths. The 

 observation consists in registering the amount of this deflection from the zero point, 

 or point in which the perpendicular line cuts the scale. It is well known that the 

 force of the wind is not constant for any great length of time. It is hence necessary 

 to take a great many observations, at short intervals, in order to obtain a correct 

 mean. In my work I noticed the deflection of the ball through fifteen minutes, 

 making a record every fifteen seconds, which gave me sixty observations for the 

 quarter of an hour. The following table taken from my note book will illustrate : 



Juue 19, 40 m. past 6, def.=20ceDtimeti'eg. 

 4014 '^ 6, "18 

 40'/2 " 6, " 20 

 40-ii " 6, " IT 

 Cup anemometer marked 15.24 m. per hour. 



I observed always the record of the anemometer for the same fifteen minutes, and 

 at the close of my work, which was continued on several days to obtain mean 

 deflections corresponding to different velocities, I had a number of such records as 

 the above, each consisting of the position of the ball at sixty di9"erent periods. 



By a well known principle of mechanics I found the force or pressure of the wind 



