Mr. J. Napier on Damp Walls. 



343 



ino-0 

 This analysis corresponds somewhat to the circumstances. Swansea is 

 upon the sea-shore, and in the immediate neighbourhood of extensive 

 copper-works, which are constantly sending into the atmosphere sulphur- 

 ous acid, often enveloping the town in a dense fog, which condenses 

 and deposits during chilly and dewy evenings sufficiently to destroy 

 vegetation. By inquiry 1 learned that some time before I occupied the 

 house, the guttering along this wall had got out of repair, so that rain 

 was admitted into the wall. Now after a short time of dry and calm 

 weather, the smoke from the copper-works having been over the town, 

 the first rain occurring after, coming off the roofs of houses, always con- 

 tained sulphate of soda, and very little chlorine, although, no doubt, the 

 soda was from sea-salt that had been decomposed — hence, this no doubt 

 was the source of the efflorescence and damp in this crack. Although 

 this analysis may not represent the general composition of efflorescence 

 on walls, the whole circumstances are suggestive of causes that may 

 produce these effects. 



Nitrates in plaster have been long known as a source of efflorescence 

 on walls ; and although I found none in the samples I tested, I have no 

 doubt they are often present, being very easily formed when organic 

 matters are present;] and, as I have mentioned, such salts may be absent 

 in one locaUty and prevail in another. Nitrates are always found to pre- 

 vail upon the walls of stables, «fec., no doubt from the soluble organic 

 matters absorbed by the wall or plaster after being built or used as a 

 stable or cowhouse. There is a practice of workmen urinating upon the 

 inside wall of a house being built : this, when continued in one place for 

 any length of time, is reprehensible, and often requires years to get quit 

 of the consequences. 



In speaking of the efflorescence and dihquescence upon walls, it is 

 often supposed that these effects are caused only by the presence of such 

 salts that have by themselves efflorescent or diliquescent properties. 

 This is a mistake. Every substance, soluble in water, that is either put 

 in or formed within a wall, produces these effects. They are brought to 

 the surface by the water, and there left dry, giving the appearance of 

 efflorescence ; and, when a more moist atmosphere occurs, the salt is 

 again dissolved, giving the appearance of deliquesence and damp. 



