Meafarement of a Baft 012 Houn flow- Heath. 439 
tinder the roof of Sir Joseph Banks’s Barn. The objedt here 
in view was the meafurement of fuch a fpace as the garden 
would conveniently admit of, when the rods were in their dry 
or contracted fiate ; and to re-meafure the fame fpace next 
morning, when the rods, being left out for the purpofe, had 
imbibed all the humidity they could from the moifiure of the 
intervening night. Accordingly, the fourth being a fine dry 
day, the fun fhining bright, and the thermometer about 68°, 
feventeen hands were arranged in the long walk, with fo much 
nicety in the fame inclined plane as to appear but like one. 
The firfi or lowermoff hand had a brafs cock fcrewed to its 
top* The two uppermofi, that is to fay, the fixteenth and 
feventeenth, were of the fixed kind, each with a brafs Aide, 
and placed only forty-five inches aftmder. The firh deal rod 
was made to butt againh the brafs cock, and the reft fuccefl- 
lively againff each other, until fifteen rod lengths were mea- 
fured off, and a fine line drawn on the hide marking the extre- 
mity of the fifteenth. That rod being removed, forty-five 
inches, taken from the brafs feale, were then laid off back- 
wards from the line on the hide of the feventeenth to, the Aide 
of the Axteenth Aand, where another fine line was drawn. 
Thus the fpace comprehended between this laA line and the cock 
on the firfi Aand, wasjuA 300 feet, or fifteen coincident rods. 
During the night of the 4th, which was very fine, the rods 
lay on the fmooth grafs. About fun- riling of the 5th there 
Came on a thick fog, which entirely difpelled about 8 o’clock. 
At 7 h. A.M. the rods being lifted from the grafs, it was per- 
ceived, that the under fides were perfeAly dry, while all the 
reff was quite wet with the dew that had fallen. The four- 
teen Aands, comprehended between the firA and fixteenth, 
having their difiances gradually reduced from twenty feet three 
Vol. LXXV. M m m inches 
