RESULTS OF INJECTION. 



673 



The more resinous a wood the less easily it is injected and 

 much resin in wood may entirely prevent injection, as for 

 instance in Scotch pinewood ; it has not yet heen ascertained 

 whether the different injecting processes afiect matters in this 

 respect. 



Beechwood with reddish false heartwood (from trees over 100 

 years old) is quite unsuitable for injection. It is not yet known 

 whether variations in the specific gravity of the same wood 

 affect matters in this respect ; this question should be decided 

 experimentally. 



5. Results of Injection. 



Reference has heen already made (p. 120) to the results ot 

 injecting railway-sleepers ; it was stated that the locality, nature 

 of the soil and wear and tear on a railway must be considered 

 in judging the durability of injected sleepers. The method of 

 injection, the anatomical structure of the wood and whether the 

 injected wood is used immediately after injection or is first kept 

 some time in store, also aff"ect its durability. 



As regards the methods of injection, the following results are 

 given by German Railways : — 



Lowenfeld found the following percentages of antiseptic sub- 

 stances in sleepers after being used for 13 years : — 



Chloride of zinc. Tar-oil. 



Oak 45 31 



Larch 51 41 



Beech 71 42 



Scotch pine 28 21 



Spruce, Silver-fir 83 55 



VOL. V. XX 



