PRACTICAL HINTS 



the simple type, which seem to have arisen independently yet 

 closely pressed against each other. 



If the pores are large and the rays seem to avoid them, the 

 latter may be said to be less than a pore's width apart, and vice 

 versa. ' These terms stand for definite divisions between the 

 species of woods, as will be seen later, and in addition form 

 convenient points d'appui when accurate measurement is not 

 immediately possible. 



Whenever the soft-tissue is arranged in bands or lines suscep- 

 tible of measurement, the same scale can be used as that arranger 1 

 for the rays. 



All the preceding matter has been written exclusively in con- 

 nexion with the transverse section. The two other sections may 

 be treated in precisely the same way, but of course the details 

 differ. The height of the rays in tangential section requires 

 measuring, and is here expressed in fractions of a mm. The 

 soft-tissue and the contents of the pores also require special 

 attention. In the case of some Conifers the horizontal resin- 

 canals are more easily located in the tangential section. 



Thin sections in a vertical direction are only possible with 

 woods with extremely fine pores, otherwise they fall into narrow 

 strips divided by all pores whose depth is greater than the 

 thickness of the section. For exhibition purposes the wood 

 may be cut in a slightly oblique direction, so that the open pore 

 does not run the whole length of the thin film, which will then 

 hold together. Coniferous woods seldom fall to pieces from this 

 cause, and many excellent sections may be picked up from the 

 floor of a joiner's shop. Similarly I have often caught a handful 

 of beautiful transverse and other sections as they streamed in 

 ribbons from the turner's chisels. 



A fascinating method of study is to be found in the use of the 

 lantern, and I am almost persuaded to say that it is preferable 

 to the microscope, as the broad grasp of the structure of the 

 wood which the lantern affords makes a great impression upon the 

 mind. Instead of the limited field of view of the microscope, 

 which necessitates the removal of one portion of the section 

 in order that another may come into view, the whole sec- 

 tion is displayed at one time, and the broad rings compared with 

 the narrow; misleading impressions being thereby dissipated. 

 After seeing a section of Oak thrown upon the screen the observer 

 feels that he will recognize the wood again even if he does not 

 possess sufficient knowledge of the structure to analyze its parts. 

 In addition, the absence of the strain upon the eyes entailed 

 by prolonged work at the microscope is avoided, and the facility 

 for pointing out and discussing details with a second person 

 makes this method of inestimable value. Again, it is scarcely 



xxxiii c 



