DRY-ROT IN TIMBER. 531 



with the seeds of decay, stimulated by moisture, the bad atmosphere 

 of an ill-contrived burial-place, and afterward by heat from the stoves 

 constantly in use. All these circumstances account satisfactorily for 

 the extraordinary and rapid growth of the fungi. 



The decayed state of a barn-floor attacked by rot is thus described 

 by Mr. B. Johnson : " An oak barn-floor which had been laid twelve 

 years began to shake upon the joists, and on examination was found 

 to be quite rotten in various parts. The planks, two and a half inches 

 in thickness, were nearly eaten through, except the outsides, which 

 were glossy and without blemish. The rotten wood was partly in a 

 state of snuff-colored, impalpable powder ; other parts were black, and 

 the rest clearly fungus. No earth was near the wood." 



An indication of dry-rot in a damp pantry will be a coating of fine 

 powder, like brick-dust, upon the shelves and earthenware, which con- 

 sists of myriads of reddish spores shed by the dry-rot fungus. When 

 these spores fall upon a wet surface, the red skin cracks at both ends, 

 and fine filaments are sent out, which grow and ramify in all directions, 

 and do their work of mischief with the timber of the closet. 



Ventilation as a remedy for dry-rot in buildings is of doubtful ser- 

 vice. If dry air be admitted in such a way as to absorb the moisture 

 which sustains it, the fungus will of course be destroyed ; but the 

 trouble is that the circulating air will carry the spores along with it, 

 and so spread the disease to unaffected parts. This is the great danger 

 with dry-rot, while the wet-rot or ordinary decay is only communi- 

 cated by actual contact. Another difficulty in ventilating for dry-rot 

 arises from the fact that air, in passing through damp places, soon 

 becomes humid, and loses its efficacy, or even does more harm than 

 good. Intestinal decay is not reached by ventilation, for the air can 

 not penetrate the spongeous exterior rottenness of timber so affected. 



The temperature at which dry-rot proceeds most rapidly is 80 

 Fahr. At 90 it is slower, and at 100 slower still, and from 110 to 

 120 is generally arrested. Its progress is rapid at 50, slow at 36, 

 and is arrested at 32 ; but will return if the temperature is again 

 raised to 50. But in a constancy and equality of temperature timber 

 will endure for ages. The wooden piles on which Venice and Amster- 

 dam are founded remain sound because of the constancy of the condi- 

 tions that surround them. Nothing is more destructive to wood than 

 partial wetting. If it be kept always wet or always dry, and at a 

 steady temperature, decay does not begin. It is recorded that a pile 

 was drawn up sound from a bridge on the Danube that parted the 

 Austrian and Turkish dominions, which had been under water fifteen 

 hundred years. It has been remarked that the part of a ship which is 

 constantly washed by bilge-water is never affected by dry-rot ; and 

 that the planking of a ship's bottom which is next the water remains 

 sound for a long time, even when the inside is quite rotten. 



As the decay of wood is chiefly due to the presence in it of sap, and 



