DIRECT MEASUREMENT OF VOLUME. 27 



feet are marked by alternate colours, alongside the tree, so as 

 to read off the distance between the lower ray of the lower 

 angle and the foot of the tree, a distance which has to be added 

 to the height taken from the table. 



The instrument is at the same time an admirable clinometer, 

 with which the angles of slopes can be measured and roads 

 laid out. 



The author has used the instrument extensively both for 



Fig. 20. Fig. 19. 



the measurement of the height of trees, and for the laying out 

 of forest roads ; he has arrived at the conclusion that it is 

 decidedly the most useful of similar instruments which are 

 known to him. 



The instrument works accurately, and much quicker than 

 the reader would imagine ; besides, its strong construction 

 renders it admirably adapted for forest work. 



6. Instruments for the Direct Measurement of the Volume. 



For this purpose the xylometer, either alone or in combina- 

 tion with a scale, is used. The method is based upon the 

 fact that a submerged body displaces a volume of water equal 

 to the volume of the body, and the instrument used is called 

 a xylometer. It consists of a graduated vessel, Fig. 19, in 



