Meafurement of a B^tfe on Hounflow-Heath. 4^^ 



tinder the roof of Sir Joseph Banks's Barn. The obje£l 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 ftate ; 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 moifture of the 

 intervening night. Accordingly, the fourth being a fine dry 

 day, the fun fliining bright, and the thermometer about 68°, 

 feventeen ftands were arranged in the long walk, with fo much 

 nicety in the fame inclined plane as to appear but like one. 

 The firft or lowermofl {land had a brafs cock fcrewed to its 

 top. The two uppermoft, that is to fay, the fixteenth and 

 feventeenth, were of the fixed kind, each with a brafs flide, 

 and placed only forty-five inches afunder. The firft deal rod 

 was made to butt againfl: the brafs cock, and the.^ft fuccef^ 

 fively againft each other, until fifteen rod lengths were mea- 

 fured off, and a fine line drawn on the Aide marking the extre- 

 mity of the fifteenth. That rod being removed, forty-five 

 inches, taken from the brafs fcale, were then laid off back- 

 wards from the line on the flide of the feventeenth to the flide 

 of the fixteenth ll"and, where another fine line was drawn. 

 Thus the fpace comprehended between this laft line and the cock 

 on the firft ftand, wasjuft 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-rlfing 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 perfectly dry, while all the 

 Teft was quite wet with the dew that had fallen. The four- 

 teen ftands, comprehended between the firft and fixteenth, 

 Jiaving their diftances gradually reduced from twenty feet three 

 VcL. LXXV, M m ra inches 



