DECAY 183 



Engineering Building at McGill University use was made of 

 very fine timbers of Douglas fir as supporting beams to carry 

 the heavy floors of the upper stories. These were seated in 

 cast-iron, flanged bed plates. Within a few years, in the room 

 used as a hydraulic laboratory, the timbers had developed dry 

 rot, which extended upwards from the base for a distance of 

 about one foot. The obvious cause was to be found in the con- 

 fined air and in the accumulation of moisture condensed from 

 the atmosphere of the room. In another case brought to my 

 notice the heavy oak roof timbers of a large building developed 

 an extensive growth of dry rot. Upon examination it was found 

 that the air of the low attic was confined and no circulation was 

 possible. Openings were at once made at opposite ends and a 

 free circulation established. The difficulty was speedily removed, 

 and there has been no recurrence of the trouble within a period 

 of about fifteen years. 



Our knowledge of the way in which and the conditions under 

 which dry rot operates makes it possible to apply effective reme- 

 dial measures with intelligence. These measures involve : 



1. Complete ventilation. 



2. Removal of all sources of alkaline and particularly of ammoniacal 

 products. 



3. A complete removal of all diseased wood. 



4. Treatment with some fungicide, such as cupric sulphate, if the condi- 

 tions are such as to make other remedies in any way ineffective. 



Finally, the observations of Dudley (14, 44), that fungi do 

 not penetrate cedar ties unless there is a good supply of air, 

 and that when the latter is cut off the growth stops, once 

 more direct attention to the nature of the effective prevent- 

 ive measures. 



From these considerations it becomes obvious that for fungi in 

 general higher temperatures offer correspondingly more favor- 

 able conditions for growth, which is also accelerated by an in- 

 crease of moisture, both operating within certain well-defined 

 limits. And we may further conclude that preventive measures 

 will be most effective under those conditions which involve low 



