1 Introduction. 



gauge is placed in the centre of tlie Makerstoun garden, with, a good exposure ; the 

 funnel mouth is 6.7 inches in diameter, 6i feet above the soil, 171 feet above the 

 level of the sea, and about 620 feet N. by E. of the gauge A. The gauges B and C 

 are about 180 feet distant. 



The gauges B and C were observed by Mr Macgall, the head gardener. 



§ 11. Anemometer. 



63. Previously to August 26. 1842, there was no vane to be relied on, and no 

 instrument for determining the force of the wind before October 21. 1842. 



The estimations of direction were generally made with a handkerchief as a 

 flag, and the force was estimated; the scale adopted being, calm 0, and boisterous 6. 

 Owing to the rarity of strong winds, the one extremity of the scale was not well 

 understood, and in the other the estimations were much too high. 



64. A vane was erected by Messrs Adie and Son, on the north wall of the 

 observatory, which, by means of a rod and geering- wheels, indicated the direction 

 on a dial-plate within the observatory. 



65. An anemometer made by Messrs Adie and Son, and invented by Mr R, 

 Adie of Liverpool,* was placed at the north-east corner. In this instrument the 

 wind blows down a tube, the opening of which, at the back of the vane, is always 

 presented to the wind. The tube is bent up at the lower extremity into a vessel 

 inverted in a cylinder full of Avater. This vessel is suspended by a cord passing 

 over a wheel, and is balanced by a weight acting on a spiral. An index attached 

 to the common axle, shews the pressure, on a dial, in pounds of pressure on a square 

 foot of surface, and leaves a moveable index at the maximum. The spiral on which 

 the weight acts is an involute of a circle, in order that the divisions on the dial 

 may be nearly of equal size throughout. 



66. Comparisons of estimated pressure, with the indications of the anemometer, 

 shewed that the estimations under 2'0 were nearly equivalent to the same quantities 

 by the anemometer, increasing above that, till 4*0 might probably be equivalent to 

 a pressure of 8*0 pounds. 



67. The way in which this instrument is observed is as follows : — About 2™ 

 before the observation hour, the highest pressure shewn by the independent index 

 is registered as the maximum pressure ; this index is then put back to zero, and 

 from 7"^ to 10°^ after, the position which the index has attained is noted as the present 

 pressure, and the index again set. 



68. It is conceived that, on the whole, this instrument is trustworthy. It is 

 occasionally, however, liable to slight derangements. A cup at the top contains 

 mercury, in which the tubular portion of the vane turns ; this fills with rain, which, 

 when frozen, prevents the vane turning its aperture to the wind. 



* Described and figured by Dr Traill in his Physical G-eography. 



