ON MR. WHEWELL’S ANEMOMETER. 159 
again replaced at the top and the Register recommenced. The 
vane V consists of two inclined planes as seen in figure 1, and 
is placed so as to be nearly in the prolongation of the axis of the 
fly. This arrangement has been found to preserve the direction 
more completely and maintain the position of the fiy in direct 
opposition to the current. The wheel-work just described is 
effectually defended from wet and other atmospheric damage 
by means of a close cover C, fig. 4, titted securely and closely 
over it. 
In the instrument hitherto in use, the registering apparatus 
D, fig. 3, is placed within a smali wood cover and the whole 
exposed to the wind on the ridge of a house or other elevated 
place. We have found it, however, necessary to set the whole 
up in a more commodious and permanent manner. A small 
lantern of wood about 3 feet square and 4 feet high, within 
which the registering apparatus is placed, fig. 3, has been 
erected on the top of a house, the circular plate A A in figs. 1 
and 2, being moveable over its summit and toward which it con- 
verges. The vane and fly are thus freely exposed to the wind 
whilst the registering apparatus descends within. 
In order to sustain the vertical axis upon which the plate A 
turns, a small beam BB, figs. 3 and 6, is placed across the 
bottom of the chamber hollowed at EK, fig. 3, in a half circle. 
The hollowed part E carries an iron ring R, figs. 3, 6 and 12, of 
about 4 inches diameter fixed to the beam B by three arms. 
Within this is a second ring of brass r, fig. 6, forming the nut 
of a third ring H, fig. 7 and 12, which can be screwed within the 
former and removed at pleasure by means of a small forked lever 
L, fig. 8. These rings preserve the position of the register 
barrel D, fig. 3, and admit of the easy motion of the axis of 
the plate A in the following way:—the lower extremity of the 
barrel terminates in a solid cap of brass ¢¢¢, figs. 3 and 5; 
this cap ¢ fits within the rings Rr, fig. 6, and there is a stud 
of brass s, fig. 5, projecting from it corresponding to a notch r, 
fig. 6, in the fixed ring; the position of the lines on the barrel 
indicating the direction of the wind is hence determined. The 
barrel D, fig. 3, is passed up through the ring R on the descend- 
ing vertical axis of the plate D, figs. 2 and 9, until its solid ring 
ft, fig.3,comes in place. It is then finally secured by screw- 
ing up the fixing ring H, figs. 7 and 12. When the barrel is 
thus secured, a screw N, figs. 3 and 5, carrying on its extremity a 
polished centre, is screwed up through the bottom of the brass cap 
of the barrel until it reaches the point of the vertical axis D, fig. 
9, of the metallic plate A A, figs. 1 and 2. It is then finally 
secured by a small nut N, figs. 5 and 12, turned up with press- 
ure against the under part of the cylinder so as to prevent 
