378 CORRECTION TO BAROMETER FOR FORCE OF WIND. 
best suited for the purpose.* The wind-gauge was of a very simple construction, 
and on the same principle as the instrument used for weighing letters, the weight 
or pressure being indicated by the compression of a spiral spring in a tube. 
Fig. 1. 















































































































































































































































































































































































































































































































































































































































































































































































































































































Lufra Cottage, Grahton, 
The wood-cut, fig. 1, represents my cottage (~~) and an open summer-house (~~) 
near it. The table in my room in the cottage, the seat of the summer-house, and 
the surface of the ground (~) close to the summer-house, are all on the same level ; 
I could thus very readily compare the indications of the barometer in these three 
different situations—that is, as sheltered by the cottage, as sheltered by the back 
only of the open summer-house, and as laid on the ground without any shelter 
whatever. f 
During calm weather I found that the indications of the barometer were iden- 
tically the same in all three positions; but that when the wind blew with any 
considerable force, the barometer in the two sheltered positions, that is, in the 
cottage and in the summer-house, were depressed as compared with the indica- 
tions of the instrument on the open ground, and that in the two sheltered posi- 
tions the depressions were in proportion to the force of the wind; and further, 
* The correction for temperature to my aneroid between 56° and 92°, is :0025 for every degree 
of increase or decrease of temperature, but the barometer is more immediately affected by a change 
of temperature than the enclosed thermometer. 
