G92 SEC. 14. METEOROLOGY. 



with the thermometer. Fixed to and passing over this wheel is a fine thread, 

 from which is suspended a pencil holder, moving up and down on a vertical 

 slide. The pencil will be raised or lowered according to the direction in 

 which the wheel is moving. The other portions of the clock-work are 

 arranged in a manner similar to that employed in the barograph. 



In the present instrument a cylinder 4^ inches, both in width and diameter, 

 is made to revolve once in Seven days. Around this cylinder is placed a 

 paper, on which the days and hours are indicated by vertical lines. The 

 cylinder is so placed that the surface of the paper is -^th of an inch away from 

 the pencil point, moving at right angles to its surface. A small striker is 

 connected with the clock-work in such a manner that at every quarter of an 

 hour it gives the. pencil a tap, striking its point against the paper. The regis- 

 tration of the temperature is thus indicated be a dotted line which can be read 

 off by a prepared scale supplied Avith the instrument. 



The scale for reading oif the register is prepared by observing the extent to 

 which the pencil rises for every 10, as indicated by a standard thermometer. 

 In this particular instrument it is found that for every 10 the pencil is raised 



f of an inch ; this gives ^ths for each degree, and the index is accordingly 

 divided to this scale. 



2S26n. Fluctuation Thermometer. Prof. Balf our Stewart. 



I v. ANEMOMETERS. 



2830. Static Anemometer, for measuring the force of the 

 horizontal component of the wind, especially of gusts. 



Scottish Meteorological Society. 



Two sets of Robinson's cup anemometers are placed one above the other on 

 one vertical spindle, so that the couple tending to turn the spindle depends 

 on the force of the horizontal component of the wind, not on its direction. 

 To the spindle is attached a spring, so that the magnitude of the couple (and 

 therefore the force of the horizontal component) is measured by the angle 

 through which the spindle is turned. This is recorded by a pencil which is 

 raised and lowered by a screw cut on the spindle. The clockwork and paper 

 for recording have not been sent. Designed by Professor Crum Brown, 

 M.D., F.R.S.E., Member of Council. 



2831. Anemometer, for ascertaining pressure of wind. 



Scottish Meteorological Society. 



This anemometer acts by lengthening (not compressing). The maximum 

 result is recorded by the thread which is fixed to the rod and pulled through 

 a hole in the brass plate fixed to the side of the box. To ascertain the 

 maximum elongation which takes place, press the thread against the plate, 

 then push in the disc until the part of the thread which has been drawn 

 through the hole is again tightened, and read off the result from the graduated 

 tube. The small disc is for high winds, the large for light. Designed by 

 Thomas Stevenson, C.E., F.R.S.E., Honorary Secretary, and described in 

 the Society's Journal, vol. iv., p. 266. 



2832. B. Ballingall's Anemometer, for continually regis- 

 tering the pressure of the wind. Scottish Meteorological Society. 



The principle of this anemometer consists in a cistern of mercury in the 

 left band chamber, with a wooden plunger, which acts in connexion with the 



