Mr. J. Napier on Damp Walls. 335 



Fi'om tliese it appears to be the physical structure that causes different 

 rates of absorptioD. The rate of progression we think worthy of further 

 notice. 



Apiece of Craigleith stone, of the sort referred to in my last paper, was 

 tried along with these, but the water did not rise one inch in twelve 

 hours. 



Placing one of these stones in the position above described, the dimen- 

 sions of the stone being seven inches high and six inches thick, and 

 dropping upon one face of the stone a little water so as to imitate a 

 shower of rain falling upon the walls of a house, the stone very speedily 

 becomes wet all over, the capillary attraction seems increased, and the 

 absorption goes on somewhat like the dotted line in the following figure : 



f^^ 



In this experiment the stone was wet all over in less than half the time 

 required to do so by capillary attraction alone, so that when a house is 

 built upon a wet foundation, the water will rise up the walls by capillary 

 attraction, and during rain this rise will be greatly increased. 



The height to which the water will rise in the wall of a house will 

 depend somewhat on the state of the atmosphere. When the evapora- 

 tion from the surface of the wall is equal to that drawn up by capillary 

 attraction, that will form the point to which it will ascend ; but this is 

 by no means a small height. I have observed in a good many houses 

 built within these five years, where the stone is not yet so black as to 

 hide the damp, that the line of damp has reached from five feet to seven 

 feet above the surface of the ground, and upon pillars at the sides of 

 doors, the water generally rises in these from one to two feet above that 

 of the ashlar wall, no doubt from its being one stone, showing how putty 

 between stones helps to retard the rise of the water. Where the found 

 has been laid upon sand or gravel the wet does not ascend so high by 

 nearly two feet. The whole length of time required for the water to 

 ascend the height of seven feet I have not positively ascertained, but, 

 when once it is up a wall, the drying is a slow process. In two instances 

 that I have strictly watched, the wet did not descend more than six inches 

 during six weeks dry weather. 



1 would suggest a very simple remedy against the capillary attraction 

 from the foundation, by putting one or two courses of common house 



