with a wire which passes through a vertical spindle, and is held tight at 

 the bottom by a slight spring; by this wire a pencil is moved trans- 

 versely to the direction in which the paper, intended to receive the 

 record, is carried by a clock. Lines are printed on the paper which 

 correspond to the different values of the pressure; the intervals of 

 these lines were adjusted by applying weights of 4 lbs., 8 lbs., &c., to 

 move the pressure plate in the same manner as if moved by the force of 

 the wind. The vanes which keep the pressure plate facing the wind 

 are made to turn the vertical spindle, and by means of a spiral groove 

 near the bottom of the spindle a rod is raised or depressed. This rod 

 'carries a pencil which is moved, when the direction of the wind changes, 

 transversely to the direction in which the paper is carried by the clock. 

 Lines are printed on the paper which correspond to the positions which 

 the direction pencil must take when the pressure plate faces the diffe- 

 rent points of the compass ; the paper has also transverse lines which 

 correspond to the positions of the pencils at eveiy hour. The direction 

 pencil was adjusted by placing it on the south line when a vane placed 

 over the transit instrument was seen, during a brisk wind, to point to 

 the meridian mark. The meridian mark of the transit instrument is 

 three miles distant from the observatory. 



The receiving surface of the rain-gauge is 30 feet above the ground, 

 and it exposes to the rain a surface of 397 6 square inches. The col- 

 lected water passes through a tube into a glass vessel ; the glass vessel 

 is made to descend by the weight of the water, and in its descent a 

 pencil is carried with it. When a quarter of an inch of rain is collected, 

 the glass receiver discharges itself by means of a modification of the 

 syphon, and the pencil ascends to the zero line. The scale of the printed 

 paper was adjusted by filling the water vessel until it emptied itself, and 

 then by weighing the water its bulk was ascertained. 



The velocity of the air is obtained by means of a horizontal windmill, 

 having for its vanes four hemispherical cups ; the action of the wind on 

 the concave surfaces exceeds that on the convex ; and Dr. Robinson 

 has found by a great number of experiments that, in a windmill thus 

 constructed, the centres of the cups move with one-third the velocity of 

 the air. The hemispheres are eight inches diameter, and the distance of 

 their centres from the axis of rotation is three feet. A vertical spindle 

 connected with the horizontal windmill is made to turn a cylinder, the 

 circumference of which is 278 inches. The paper which receives the 

 record is stretched tight over the cylinder, and for every inch of paper 

 worked off the centres of the hemispheres travel l'2-75 miles, or 38*25 



