16 



BULLETIN 510, U. S. DEPARTMENT OF AGRICULTURE. 



1 to 2 feet (fig. 16) or set on short posts. A few of the best mills 

 make use of concrete piers for this purpose. The latter type of 

 foundation ^YOulcI be gi'eatly improved by the use of stringers treated 

 with a wood preservative. 



The dangers arising from partially rotted foundations are evident, 

 as has been seen from the earlier discussion of the activities of wood- 

 destroying fungi. Where wood blocks are used to support the skids, 

 fungi often progress directly from the moist soil upward, in this way 

 frequently infecting the skids, thus adding the possibility of direct 



mycelial infection to 

 that of spore infec- 

 tion. The infected 

 skids themselves are 

 dangerous, since the 

 fungous mycelium 

 can progress directly 

 from them to the bot- 

 tom of the lumber 

 piles (PI. IV, fig. 3; 

 text fig. ir). Once 

 started, and the 

 weather conditions 

 being warm and 

 moist, such infections 

 may pass through an 

 entire stack. In con- 

 sidering the menace 

 of infected skids, we 

 must also not lose 

 sight of the fact that 

 such timbers are a 

 prolific source of 

 fruit bodies (PI. Ill, 

 fig. 3) with their 

 many spores, to be 

 borne up into the 

 lumber piles either directly by the wind or by convection currents 

 which occur in relatively still air. The proof of this latter form of 

 air currents is often before us in the form of rising mists or fogs. 



The first requisite in building foundations is to get them well off 

 the ground, so as to allow ample ventilation beneath, which will 

 dry out the timbers themselves as well as the soil below. A height 

 of at least 24 inches from the top of the skids to the surface of the 

 ground should be adhered to. 



Fu;. 12. — Rotten base of an old hardwood stack upon 

 •Which sound lumber has been piled. This is a most 

 insanitary practice, as fungous infection will be spread 

 both by the contact of the diseased with the sound lumber 

 and indirectly by the production of fruit bodies and 

 spores, the latter blowing about, reaching sound mate- 

 rial, and germinating to produce new infections. 



