432 Col. Beaufoy on a new Wind Guage, [Dec. 



pressed backwards, it draws the chain, and turns the barrel and 

 fusee round, drawing up the weight, which acts with an increas- 

 ing power as the screen is forced further backwards, by the 

 silken cord winding upon a larger radius of the fusee. The axis 

 of the fusee is furnished with a ratchet wheel (and pall) to retain 

 it, and prevent any retrograde motion ; in order that the index 

 upon the axis of the fusee may indicate the extreme point at 

 which the screen had been forced by the wind at any period of 

 the experiment. 



The construction of the apparatus is particularly described in 

 Plate XII. Fig. 1 represents a perspective view of the whole 

 apparatus, placed in a situation to act; it is mounted upon a 

 mahogany tripod stand, similar to the portable instruments used 

 in surveying. The upper part of the apparatus is surmounted by 

 a light stick bearing a small silk Hag upon its top, to show the 

 direction or quarter of the wind, in order to place the surface of 

 the screen perpendicular to the direction of the wind's motion, 

 previous to making an experiment upon the force of it. 



Fig. 2, represents a side elevation of the apparatus with only 

 part of the sliding bar, 13 B, shown. 



Fig. 3, a plan of the whole apparatus. 



Fig. 4, a side elevation with some parts of the frame removed 

 to explain the internal works ; and figures 5, 6, and 7, represent 

 transverse sections of the apparatus taken at different parts of 

 its length. The same letters of reference serve to | denote 

 similar parts upon each. A A, the screen which is attached 

 by a screw pin p to the extreme end of the bar B, B. a a, 

 b b, represent the four rollers which serve to guide the bar 

 horizontally; and cc,d d, those which guide it sideways, as 

 seen in fig. 3. C and D, the chain, one end of which is fixed 

 to the underside of the bar at C, and the other end winds round 

 the barrel D upon the axis of the fusee F. G shows a silken 

 cord, which winds round the fusee, having a weight H hooked to 

 the lower end of it ; E, the ratchet wheel upon the fusee axis, 

 furnished with a click or pall, I, to prevent the descent of the 

 weight, after it has been drawn up to any particular point by the 

 action of the wind upon the screen A. K K, represent two bra>s 

 plates, which receive and support the axis of the fusee, as also 

 the axis of the pall I, and the pivots of the two rollers, a a. The 

 plates, K K, are kept parallel by three small pillars, S S S (in 

 the manner of clock movements), and are attached by screw 

 bolts, e e, to the wooden block M, which forms the principal 

 frame of the apparatus. The wood rises up at N, and is hol- 

 lowed cut to contain the small rollers, b b ; the pivots of which 

 turn in brass plates, h h, screwed on each side of the block, as 

 seen by the dotted lines in the plan, fig. 3. 



The vertical rollers, d d, are supported by brass cocks, i i, 

 screwed against the plates, h h ; the pivots of the other vertical 

 rollers, c c, also turn in cocks, Ic I;, screwed to the plates K K, 

 as seen in the transverse section, fig. 5. O, shows a circular 



6' 



