Rondelet says, “The woodwork of the church of St. Paul, outside the city walls, which was destroyed by fire in 1823, was erected as far back as the fifth century.” Although the atmosphere surrounding the framework was often at once warm and damp, yet it was never stagnant. It should be remembered that 500 people in a church during two hours give off fifteen gallons of water into the air, which, if not carried away, saturates everything in the building after it has been breathed over and over again in conjunction with the impurities it contains collected from each individual.
Fever, scrofula, and consumption arise in many instances from defective ventilation.
The signs of decay in timber are, as has been stated, fungi. Some of them now and then are microscopic, and owe their existence to the sporules deposited on the surface; while fermentation, generated by prolonged contact with warm, damp, and stagnant air, is as a soil where seeds sow and nourish themselves.
Mr. McWilliam, in his work on dry rot, states that if the temperature be very low or very high, the effects are the same with respect to the growth of fungi. At 80° dry rot will proceed rapidly, at 90° its progress is more slow; at 100° it is slower still, and from 110° to 120° it will in general be arrested. It will proceed fast at 50°; it may be generated at 40°; its progress will be slow at 36°; and is arrested at 32°, yet it will return if the temperature is raised to 50°.
Dry rot externally first makes its appearance as a mildew, or rather a delicate white vegetation, that looks like such. The next step is a collecting together of the fibres of the vegetation into a more decided form, somewhat like hoar frost; after which it speedily assumes the leathery, compact character of the fungus, forming into leaves, spreading rapidly in all directions, and over all materials, and frequently ascending the walls to a considerable height, the colour variable—white, greyish white, and violet, light or decided brown, &c.
In the section of a piece of wood attacked by dry rot a microscope reveals minute white threads spreading and ramifying throughout its substance; these interlace and become matted together into a white cottony texture, resembling lint, which effuses itself over the surface of the timber; then in the centre of each considerable mass a gelatinous substance forms, which becomes gradually of a yellow, tawny hue, and a wrinkled, sinuated porous consistence, shedding a red powder (the spores) upon a white down; this is the resupinate pileus, the hymenium being upwards, of Merulius lachrymans, in its perfect and matured state. Long before it attains to this, the whole interior of the wood on which it is situated has perished; the sap vessels being gradually filled by the cottony filaments of the fungus; no sooner do these appear externally than examination proves that the apparently solid beam may be crumbled to dust between the fingers; tenacity and weight are annihilated.
Dr. Haller says that seven parts in eight of a fungus in full vegetation are found by analysis to be completely aqueous.
The strength of fungi is proportionate to the strength of the timber the cohesive powers and nutritive juices of which they absorb; and according to the food they receive so they are varied and modified in different ways, and are not always alike. Different stages of corruption produce food of different qualities, and hence many of the different appearances of fungi. One takes the process of corruption up where another leaves it off, and carries it forward and farther forward to positive putrefaction.
The forms which fungi assume are extremely diversified; in some instances we have a distinct stem supporting a cap, and looking somewhat like a parasol; in others the stem is entirely absent, and the cap is attached either by its margin, and is said to be dimidiate, or by its back, or that which is more commonly its upper surface, when it is called resupinate. In some species the form is that of a cup, in others of a goblet, a saucer, an ear, a bird’s nest, a horn, a bunch of coral, a ball, a button, a rosette, a lump of jelly, or a piece of velvet.
Decomposition takes place without fungus where the timber and the situation are always moist, as in a close-boarded kitchen floor, where it is always dry, or very nearly so, and where it is alternately wet and dry, cold and hot. When the decomposition is affected with very little moisture, and no fungus, the admission of air will generally prevent further contamination; but where there is abundance of moisture, rottenness, and fungus, a small quantity of air will hasten the destruction of the building.