64 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTUKAL SOCIETY. 



serve as a valuable check on the experiments of other 

 departments. 



This department possesses a complete equipment for prepar- 

 ing sections and photomicrographs of wood, and is making a 

 collection of North American woods. The specimens are in the 

 form of half-logs 4 feet long, with bark attached, cut so as to 

 display the transverse, radial, tangential and obliquely tangential 

 surfaces. 



3. IVood Prescrvatio7i and (8) Pathology Departments. — The 

 wood of these two departments is so closely connected that it 

 is simpler to describe them together. The Wood Preservation 

 Laboratory contains a very complete equipment for testing the 

 various problems of wood preservation by treating the wood 

 with materials which increase its durability. 



These problems may be divided broadly into two classes : 

 {a) Those dealing with the preservatives themselves, their 

 effect on the wood and their efficiency in resisting 

 fungi, insects and fire. 

 {b) Those concerned with the methods of forcing the 

 preservative into the wood. 



{a) In the study of the first of these problems the preservatives 

 are analysed and fractionally distilled in the chemical laboratory. 

 The efficiency of each preservative and its different fractions 

 is then tested by subjecting woods treated with them to the 

 action of wood-destroying fungi or animals, and noting their 

 relative powers of resistance. The effects of weather on the 

 preservative in the treated specimens are also investigated and 

 taken into account in judging efficiency. 



The efficiency of each preservative or of its fractional 

 distillates is also tested by making culture media of wood- 

 destroying fungi to which the preservatives are added in different 

 percentage strengths. The extent to which the fungus succeeds 

 in growing in such media affords an indication of the efficiency 

 of the preservative. 



Experiments of a similar kind on a larger scale are alsa 

 being attempted in a fungus pit which has been specially 

 constructed below the floor in one corner of the Wood Preserva- 

 tion Laboratory. 



ij)) The equipment for studying the second class of problems, 

 viz., the methods of impregnating the woods with the different 

 preservatives, is very complete. There are four sizes of pressure 



