MAKING SECTIONS. 



445 



wards be easily separated. The process of cutting consists in raising 

 the wood by the micrometer screw, so that the thinnest possible slice 

 may be taken off by the knife ; after a few thick slices have been re- 

 moved to make the surface level, a small quantity of water or spirit 

 may be placed upon it ; the screw is then to be turned one or more 

 divisions, and the knife passed over the wood until a slice is removed ; 

 this, if well wetted, will not curl up, but will adhere to the knife, from 

 which it may be removed by pressing blotting-paper upon it, or by 

 sliding it off upon a piece of glass by means of a wetted finger. The 

 plan generally adopted is to have a vessel of water by the side of the 

 machine, and to place every section in it : those that are thin can then 

 be easily separated. from the thick by their floating more readily in the 

 water ; and all that are good, and not immediately wanted, may be put 

 away in bottles with spirit and water, and preserved for future exami- 

 nation. If the entire structure of any exogenous wood is required to 

 be examined, the sections must be made in at least three different 

 ways ; these may be termed the transverse, the longitudinal, and the 

 oblique, or, as they are sometimes called, the horizontal (seen at No. 5, 

 fig. 211), yertical, and tangental : each of these will exhibit different 

 appearances, as may be seen upon reference to fig. 215. 6 is a vertical 

 section through the pith 

 of a coniferous plant : this 

 exhibits the medullary 

 rays, which are known to 

 the cabinet-maker as the 

 silver grain ; and at e is a 

 magnified vi^w of a part 

 of the same : the woody 

 fibres- are seen with their 

 dots I, and the horizontal 

 lines k indicating the me- 

 dullary rays cut length- 

 wise j whilst at c is a tan- 

 gental section, and/a por- 

 tion of the same magnified : the openings of the medullary rays m m, and 

 the woody fibres with vertical slices of the dots, are to be seen. Very 

 instructive preparations may be made by cutting oblique sections of the 

 stem, especially when large vessels are present, as then the internal 

 structure of the walls of some of them may oftentimes be examined. 

 The diagram above given refers only to sections of a pine ; all exoge- 

 nous stems, however, will exhibit three different appearances, according 



'. 215. 



