58 TRANSACTIONS OF THE [XOV. 23, 



a]ii)ear afterward on tlie surface as previously tloscribcd. Nitric 

 acid, and also the alkali ammonia, acr similarh'. Tlieir destructive 

 effect on the mortar and cement, joints is especially noticeable 

 on the brick-work of the tops of chimneys that are in contact 

 witli the outflowing gases resulting from the fires beneath. 



(5) Effects of these salts on building materials. — The alkaline 

 property of some of these salts is very destructive to brick, stone, 

 cement, and mortar, completely disintegrating them, as may be 

 seen by cai'efnl examination of the jdaces where they show; nor 

 can linseed oil, jiamts, or simihir compositions withstand them; 

 the oil being saponified by the alkali and rendered useless, so 

 that the i>aint is destroyed and falls away. I have seen these 

 salts in the walls of buildings in England, nearly 150 years old, 

 still active and troublesome. In Philadelphia on October 4th, 

 18b3, I noticed the peculiai'ly white ap])earancc of a great number 

 of the houses, and asked if they had been whitewashed. I then 

 learned that the whiteness was wholly due to an extraordinary 

 quantity of these salts on the surface of the walls, caused by a 

 three days' rain-fall that hud occurred a few days before, and had 

 completely saturated the brickwork, which, upon drying out had 

 produced the efflorescence. It by no means follows that the 

 brick, cement, and lime severally are not good, because they 

 contain these salts, however undesirable these salts nuiy be; in 

 fact, 1 have constantly observed them in the very best qualities 

 of each. 



(6) Eesponsibility of the ]>rofession and trades. — Architects 

 and builders are often blamed and held amenable for discolora- 

 tions on buildings, and most unjustly so, when they are no more 

 responsible for dirt settling upon and staining the walls, or for 

 the salts that ap})ear thereon, than are the shoemakers for our 

 shoes getting soiled when we walk in a muddy street, or glaziers 

 for our windows getting dirty from rain and dust. 



Water will penetrate an ordinary brick ; it will dissolve the 

 salts in the walls, it will bring the same to the surface and 

 evaporate and leave the salt to crystallize. Dust will float in the 

 air and settle on exposed surfaces, and if rain can fall upon 

 them, it will most assuredly penetrate and permanently stain 

 them. These are natural causes and effects, and no one can be 

 justly and reasonably blamed for such things happening. 



About a year ago, I was requested to examine a large new 

 building in this city; the front was of a light yellow brick. The 

 owner was moving his goods into it. It had become, as usual, 

 stained, and the owner was retaining a part of the money, re- 

 fusing to pay either architect or builder because of these stains. 

 After a careful examination, I told him that neither of them 

 were responsible; that the front faced the North, had been very 



