SELF-REGISTERING ANEMOMETER AND RAIN-GAUGE. 127 



An Account of the Self-registering Anemometer and Rain-gauge 

 erected at the Liverpool Observatory in the Autimm q/'1851, ivith 

 a Summary of the Records for the years 1852, 1853, 1854, and 

 1855. By A. FoLLETT Osler, F.R.S. 

 It was at the Meeting held in Liverpool in 1837, that my self-registering 

 Anemometer and Rain-gauge were first introduced to the notice of the 

 British Association. Never having previously seen any instruments designed 

 to accomplish similar purposes, I was at the outset much at fault, especially 

 with regard to the Anemometer, and soon became sensible that to construct 

 one that would record light winds with any degree of accuracj', and at the 

 same time effect the registration of storms and hurricanes, would necessarily 

 involve many difficulties. Subsequent experience has enabled me to over- 

 come most of these, and I believe that the instruments now under the able 

 superintendence of Mr. Hartnup, at the Liverpool Observatory, of which I 

 subjoin a brief description, have for these four years past registered an 

 accurate and complete series of results. 



The direction of the wind is obtained by means of a wheel-fan, similar to 

 that at the back of a windmill ; this preserves a steady action and is very free 

 from oscillation. Its motion is connected with the recording portion of 

 the instrument, by means of a tube carrying at the lower end a large screw 

 or spiral groove *, to which the direction pencil is attached ; the motion given 

 by this means causing a pencil to trace the direction of the wind on a sheet 

 of paper stretched on a vertical cylinder, which is moved at a uniform rate by 

 means of a clock. The paper is engraved with perpendicular lines to show 

 the time, and with horizontal lines to indicate the direction. 



The force of the wind is ascertained by means of a circular plate having 

 an area of four square feet, which is kept by the vane at right angles to the 

 current of the wind. This plate is suspended by four light springs, imme- 

 diately behind which are four strong ones, the whole being so arranged that 

 the light springs are in action in light winds, but as the force increases the 

 pressure is gradually received on the strong ones. To this pressure-plate is 

 attached a wire which communicates with a recording pencil below, that 

 marks off the force of the wind in pounds avoirdupois per square foot on the 

 margin of the paper on which the direction is recorded. 



For the method employed for ascertaining the amount of horizontal motion 

 of the air, I am indebted to Dr. Robinson, who first introduced that beauti- 

 ful and simple arrangement of the revolving hemispherical cups. These 

 cups revolve in a horizontal plane, the difference in resistance between the 

 convex and concave surfaces securing their constant revolution in one di- 

 rection at a velocity of one-third of that of the airf. Dr. Robinson has 

 fully explained the laws that regulate their motion in a paper to the Royal 

 Irish Academy (vol. xxii. part 3). The plan for registration, however, 



* In the first instruivicnt the paper was placed horizontally, and the motion conveyed to 

 the direction pencil by means of a rack and pinion ; but finding a vertical position on several 

 accounts more convenient, I made use of the screw movement described above, which had 

 been pre^'iously suggested in a conversation with the late Mr. Henry Knight, of Birmingham. 



t In the first instrument which I erected at Birmingham, the velocity of the airwas obtained 

 by means of a light wheel three feet in diameter, placed horizontally, having fans resembling 

 those on a water-wheel, the greater portion of the wheel being screened by a cover with a 

 vane attached to it, so that only a few of the fans were exposed to the action of the wind. 

 The number of revolutions was recorded on the same paper on which the other registers 

 were taken, by communicating their motion, reduced by screw movements, to a spiral incline, 

 which propelled a pencil at right angles to the direction in which the paper was moved by 

 the clock. I found, however, that the high velocity at which it revolved interfered so much 

 with its durability and accuracy, that after a few months I discontinued the use of it. I have 



