5 22 



Modes of ascertaining the Heights of Trees. 



be figured to correspond with its place on the original scale of 

 feet. The centre of the quadrant (c) is the point the plummet is 

 to be suspended from ; and [d c) is the edge to be brought in a 

 line with the object the height of which is required. In the dia- 

 gram I have imagined a base line of 100 feet, as I think that a 

 distance which will be generally suitable ; but each person can 

 arrange that distance according to his own ideas. 



Should it happen that the object cannot be seen from a station 

 at the distance of 100 feet, go twice as far off; take the height 

 as before, and double the figuring on the graduated scale; or, if 

 more convenient, go in to half the distance, and then halve the 

 In either case the result will be correct. 



A quadrant thus arranged will only be available for the above- 

 mentioned stations ; but a series of concentric scales can be 

 formed on the same quadrant, arranged for other stations at 

 various distances from the object; and this will in no way inter- 

 fere with the simplicity of the instrument, though it will make it 

 applicable to nearly every possible case or situation. Fig. 93. is 

 a rough sketch of a quadrant so arranged. 



figuring. 



I have never either seen or heard of this instrument having 

 been made or used by any one but myself; but it is so simple, 

 that it is very likely that it has been thought of and acted on 

 before. — Bichard Varden. Worcester, September 7. 1835. 



