FOR DETACHED OBSERVATORIES. 



529 



rain guage Z. The pins for registering these indications are also of 

 ebonite, and may run with considerable friction over their scales, since 

 there is in these instruments a superabundance of motive force. 



In the case of the wind vane, which, by its sudden and extended oscil- 

 lations, may often endanger the gold "point" of which we are about to 



Fig. IV. 



Fig. IV h. 



speak, I propose to use a strained rubber band around the two wheels, 

 instead of a chain or leather band, in order to lessen the intensity of 

 tin' si locks. 



The divided limb MMMM may be made of metal or any other ma- 

 terial, but its outer edge should be of platinum or of brass, heavily gold- 

 plated, because through it the galvanic current is made and broken, and 

 consequently it is necessary to preserve it from oxidation. In front of 

 the graduated limb is a clock, of which Fig IV & shows only the minute 

 hand R R, the arbor of which is in the prolongation of the axis around 

 which the several indexes turn. This minute hand is of metal, and car- 

 ries at its extremity a metal "point" ,r, which glides over the platinum 

 or gilt rim of the divided circle. The rim being connected by a conduct- 

 13. Mis. 54 34 



