l INTRODUCTION. 
gauge is placed in the centre of the Makerstoun garden, with a good exposure; the 
funnel mouth is 6.7 inches in diameter, 63 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 € 
are about 180 feet distant. 
The gauges B and C were observed by Mr Macea 1, 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 AprE and Son, and invented by Mr R. 
ApiE 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 water. 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 Trarxx in his Physical Geography. 
