BUILDING AND ORNAMENTAL STONES. 353 



the euUiblatiires and the " tablettes " of balustrades iipuu which the 

 water drips or runs more slowly. It is for this reason that architeets 

 advocate the under-throating of window sills and other projections in or- 

 der that the water may be thrown ofl' from the building and not allowed 

 to run down over the face of the stone beneath. The disastrous effects 

 from neglect of this proceeding have been dwelt upon by Julien in 

 reference to buildings in New York City. The author has in mind 

 the costly residence of a former Cabinet minister in Washington in 

 which the middle portion of the brownstone entablatures are almost 

 continually wet throughout the winter months by the soaking througli 

 of water from above. The stone steps in the same house are constantly 

 wet and show a whitish efflorescence. Both these defects are liable to 

 appear in so porous a material, but might in large part have been 

 averted by exercising proper care in building. 



It may not be out of place here to comment on the folly of placing 

 iron railing on steps, platforms, etc., of finely finished granite, since in 

 spite of i)aint and other means of protection the iron invariably rusts, 

 staining and badly defacing the entire surface beyond possibility of 

 repair. 



The method of dressing a stone has an important bearing upon its dura- 

 bility. As a rule it may be set down that the less jar from heavy 

 ])oundiug the surface is subjected to the better; this for the reason that 

 the constant impact of the blows tend to destroy the adhesive or cohesive 

 power of the grains, and thus renders the stone more susceptible to 

 atmospheric influences. It is stated by Mr. Batchen that some of the 

 dolomites used in Chicago, although apparently perfectly sound when 

 quarried, shortly showed a tendency to scale on exposure. On examina- 

 tion it appears that in dressing these surfaces were both ax- and bush- 

 hammered, the implements used weighing from 8 to 12 pounds, and capa- 

 ble of striking blows of not less than 150 or 200 pounds. The effect of 

 these heavy blows was to "stun"* the surfaces for the depth of from 

 one-sixteenth to one-eighth, or even one-fourth, of an inch, and on ex. 

 posure scaling- resulted, leaving them ragged and unsightly. Sawn 

 surfaces of the same stone, on the contrary, do not usually show the 

 slightest tendency to scale. 



Kesults such as these, are what one is naturally led to expect, but 

 further experiments are necessary before it will answer to speak too 

 positively regarding the merits or demerits of various kinds of finish. 

 With compact crystalline rocks like the granites and diabases it would 

 seem probable that rock-faced work, untouched by chisel or hammer, 

 would prove most durable, since the crystalline facets thus exposed are 

 best fitted to shed moisture and the natural adhesion of the grains has 

 not been disturbed t. 



*/. «., to break the gruiiia and produce minute fissures. 



t The single oxpcrimont of Pfaff, iu which a polished grauito was found to weather 

 more rapidly than one unpolished, sooms too anomalous to ho accepted until further 



H. Mis. 170, pt. 2 23 



